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Why We Sleep

📃The Accompanying PDF

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🔖How would I describe this book in 1 sentence?

Your complete guidebook to sleep and the physiology of the human brain.

🗺️What was the role of this book in my journey?

I started paying more attention to sleep when I began learning more about health and productivity during summer 2020.

It became even more crucial in February-March 2021 when I decided to switch my sleeping schedule from 0:00-8:00 to 22:00-6:00. I encountered a lot of obstacles during that process and wanted to learn if everything I did was right or if there are any other useful strategies to improve sleep.

This book is actually 35% about sleep and 65% about the human brain, which I was pleasantly surprised with. Earlier that year, I wanted to research how the human brain works with memory, emotions, concentration, etc. but found very little information about it online. In this book, I learned almost everything I wanted to know about how the brain operates.

The key improvement is that now I can rationalize and explain certain things happening to my mind and my body and pinpoint exact causations of them. For example, in the past I might have mental gaps during one day and mental breakthroughs during others. I couldn't explain this inconsistency and just went along with it. Now I can draw correlations between how I feel my self and how I sleep, what I eat, and what I do.

And surely, incorporating some principles from the book allows me to fight the occasionally striking insomnia.

💡Key Insights

Insights

  1. There are two main factors that determine when you want to sleep and when you want to be awake. As you read these very words, both factors are powerfully influencing your mind and body. The first factor is a signal beamed out from your internal twenty-four-hour clock located deep within your brain. The clock creates a cycling, day-night rhythm that makes you feel tired or alert at regular times of night and day, respectively. The second factor is a chemical substance (adenosine) that builds up in your brain and creates a “sleep pressure.” The longer you’ve been awake, the more that chemical sleep pressure accumulates, and consequentially, the sleepier you feel. It is the balance between these two factors that dictates how alert and attentive you are during the day, when you will feel tired and ready for bed at night, and, in part, how well you will sleep.
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  3. The likelihood of breaking an Olympic record has been clearly tied to time of day, being maximal at the natural peak of the human circadian rhythm in the early afternoon
  4. Wakefulness and sleep are under the control of the circadian rhythm, and not the other way around. That is, your circadian rhythm will march up and down every twenty-four hours irrespective of whether you have slept or not. Your circadian rhythm is unwavering in this regard
  5. Melatonin helps regulate the timing of when sleep occurs by systemically signaling darkness throughout the organism. But melatonin has little influence on the generation of sleep itself: a mistaken assumption that many people hold
  6. Caffeine tricks you into feeling alert and awake, despite the high levels of adenosine that would otherwise seduce you into sleep
  7. Sleep debt accumulates. When you don’t get enough sleep, one consequence among many is that adenosine concentrations remain too high. Like an outstanding debt on a loan, come the morning, some quantity of yesterday’s adenosine remains. You then carry that outstanding sleepiness balance throughout the following day
  8. Brain keeps track of time while you are sleeping. While your conscious mapping of time is lost during sleep, at a non-conscious level, time continues to be cataloged by the brain with incredible precision
  9. Humans don’t just sleep, but cycle through two completely different types of sleep: NREM (non–rapid eye movement) and REM (rapid eye movement). REM sleep, in which brain activity was almost identical to that when we are awake, was intimately connected to the experience we call dreaming, and is often described as dream sleep. NREM sleep is a deep sleep without any dreaming experience
  10. The key function of deep NREM sleep, which predominates early in the night, is to do the work of weeding out and removing unnecessary neural connections. In contrast, the dreaming stage of REM sleep, which prevails later in the night, plays a role in strengthening those connections
  11. When it comes to sleep, there is no such thing as burning the candle at both ends—or even at one end—and getting away with it
  12. Regardless of the amount of recovery opportunity, the brain never comes close to getting back all the sleep it has lost
  13. Brain as an information processing system
    1. Brain as an information processing system

    2. The steady, slow, synchronous waves that sweep across the brain during deep sleep open up communication possibilities between distant regions of the brain, allowing them to collaboratively send and receive their different repositories of stored experience
    3. You can think of each individual slow wave of NREM sleep as a courier, able to carry packets of information between different anatomical brain centers. One benefit of these traveling deep-sleep brainwaves is a file-transfer process. Each night, the long-range brainwaves of deep sleep will move memory packets (recent experiences) from a short-term storage site, which is fragile, to a more permanent, and thus safer, long-term storage location. We therefore consider waking brainwave activity as that principally concerned with the reception of the outside sensory world, while the state of deep NREM slow-wave sleep donates a state of inward reflection—one that fosters information transfer and the distillation of memories.
    4. Wake state = reception. Experiencing and constantly learning the world around you
    5. NREM sleep = reflection. Storing and strengthening those raw ingredients of new facts and skills
    6. REM sleep = integration. Interconnecting these raw ingredients with each other, with all past experiences, and, in doing so, building an ever more accurate model of how the world works, including innovative insights and problem-solving abilities
  14. The brain paralyzes the body so the mind can dream safely
  15. Without exception, every animal species studied to date sleeps, or engages in something remarkably like it
  16. Individuals who are deliberately fasting will sleep less as the brain is tricked into thinking that food has suddenly become scarce
  17. You experience a state of drowsiness and lack of alertness during midafternoon hours because humans were programmed to take short 30-60 minute naps during that time
  18. The true pattern of biphasic sleep—for which there is anthropological, biological, and genetic evidence, and which remains measurable in all human beings to date—is one consisting of a longer bout of continuous sleep at night, followed by a shorter midafternoon nap.
  19. The coolheaded ability to regulate our emotions each day—a key to what we call emotional IQ—depends on getting sufficient REM sleep night after night
  20. REM-sleep dreaming state fuels creativity
  21. Prior to birth, a human infant will spend almost all of its time in a sleep-like state, much of which resembles the REM-sleep state.
  22. REM sleep is essential for the brain formation process. The time of life when REM sleep is greatest is the same stage when the brain is undergoing the greatest construction
  23. Every hour of REM sleep appears to count, as evidenced by the desperate attempt by a fetus or newborn to regain any REM sleep when it is lost. Blocking or reducing REM sleep in newborn animals hinders and distorts brain development, leading to an adult that is socially abnormal
  24. When babies consume alcohol-laced milk, their sleep is more fragmented, they spend more time awake, and they suffer a 20 to 30 percent suppression of REM sleep soon after
  25. The proportion of REM sleep decreases in early childhood while the proportion of NREM sleep actually increases, even though total sleep time decreases
  26. Deep NREM sleep helps in preparing brain for the adulthood
  27. Asking your teenage son or daughter to go to bed and fall asleep at ten p.m. is the circadian equivalent of asking you, their parent, to go to sleep at seven or eight p.m. No matter how loud you enunciate the order, no matter how much that teenager truly wishes to obey your instruction, and no matter what amount of willed effort is applied by either of the two parties, the circadian rhythm of a teenager will not be miraculously coaxed into a change. Furthermore, asking that same teenager to wake up at seven the next morning and function with intellect, grace, and good mood is the equivalent of asking you, their parent, to do the same at four or five a.m.
  28. Older adults who want to shift their bedtimes to a later hour should get bright-light exposure in the late-afternoon hours
  29. The parts of our brain that ignite healthy deep sleep at night are the very same areas that degenerate, or atrophy, earliest and most severely as we age
  30. Sleep is not the absence of wakefulness. It is far more than that
  31. Sleep has proven itself time and again as a memory aid: both before learning, to prepare your brain for initially making new memories, and after learning, to cement those memories and prevent forgetting.
  32. People who take a nap between morning and evening learning sessions, remember 20% more than those who don't
  33. During sleep, memories transition from short-term storage (hippocampus) to long-term storage site (cortex)
  34. Memory retention benefit of between 20 and 40 percent being offered by sleep, compared to the same amount of time awake.
  35. The more deep NREM sleep, the more information an individual remembered the next day
  36. Artificial memory enhancements during sleep
    1. Memory enhancements

    2. You can enhance your memory retention during sleep by using sleep stimulation, and targeted memory reactivation
    3. Experiment 1: Enhancing brainwaves using electrical stimulation

      Since sleep is expressed in patterns of electrical brainwave activity, sleep stimulation approaches began by trading in the same currency: electricity. In 2006, a research team in Germany recruited a group of healthy young adults for a pioneering study in which they applied electrode pads onto the head, front and back. Rather than recording the electrical brainwaves being emitted from the brain during sleep, the scientists did the opposite: inserted small amounts of electrical voltage. They patiently waited until each participant had entered into the deepest stages of NREM sleep and, at that point, switched on the brain stimulator, pulsing in rhythmic time with the slow waves. The electrical pulsations were so small that participants did not feel them, nor did they wake up. But they had a measurable impact on sleep. Both the size of the slow brainwaves and the number of sleep spindles riding on top of the deep brainwaves were increased by the stimulation, relative to a control group of subjects who did not receive stimulation during sleep. Before being put to bed, all the participants had learned a list of new facts. They were tested the next morning after sleep. By boosting the electrical quality of deep-sleep brainwave activity, the researchers almost doubled the number of facts that individuals were able to recall the following day, relative to those participants who received no stimulation. Applying stimulation during REM sleep, or during wakefulness across the day, did not offer similar memory advantages. Only stimulation during NREM sleep, in synchronous time with the brain’s own slow mantra rhythm, leveraged a memory improvement.

    4. It is possible to achieve nearly 100 percent memory enhancement the next morning using proper electrical stimulation during NREM sleep.
    5. Experiment 2: Enhancing memory retention using audiowaves

      Other methods for amplifying the brainwaves of sleep are fast being developed. One technology involves quiet auditory tones being played over speakers next to the sleeper. Like a metronome in rhythmic stride with the individual slow waves, the tick-tock tones are precisely synchronized with the individual’s sleeping brainwaves to help entrain their rhythm and produce even deeper sleep. Relative to a control group that slept but had no synchronous auditory chimes at night, the auditory stimulation increased the power of the slow brainwaves and returned an impressive 40 percent memory enhancement the next morning.

    6. It is possible to achieve 40 percent memory enhancement the next morning using sound stimulation during NREM sleep.
    7. Slow rocking increased the depth of deep sleep, boosted the quality of slow brainwaves, and more than doubled the number of sleep spindles
    8. Experiment 3: Targeted memory reactivation

      Before going to sleep, we show participants individual pictures of objects at different spatial locations on a computer screen, such as a cat in the lower right side, or a bell in the upper center, or a kettle near the top right of the screen. As a participant, you have to remember not only the individual items you have been shown, but also their spatial location on the screen. You will be shown a hundred of these items. After sleep, picture objects will again appear on the screen, now in the center, some of which you have seen before, some you have not. You have to decide if you remember the picture object or not, and if you do, you must move that picture object to the spatial location on the screen where it originally appeared, using a mouse. In this way, we can assess whether you remember the object, and also how accurately you can remember its location. But here is the intriguing twist. As you were originally learning the images before sleep, each time an object was presented on the screen, a corresponding sound was played. For example, you would hear “meow” when the cat picture was shown, or “ding-a-ling” when the bell was shown. All picture objects are paired, or “auditory-tagged,” with a semantically matching sound. When you are asleep, and in NREM sleep specifically, an experimenter will replay half of the previously tagged sounds (fifty of the total hundred) to your sleeping brain at low volume using speakers on either side of the bed. As if helping guide the brain in a targeted search-and-retrieve effort, we can trigger the selective reactivation of corresponding individual memories, prioritizing them for sleep-strengthening, relative to those that were not reactivated during NREM sleep. When you are tested the following morning, you will have a quite remarkable bias in your recollection, remembering far more of the items that we reactivated during sleep using the sound cues than those not reactivated. Note that all one hundred of the original memory items passed through sleep. However, using sound cuing, we avoid indiscriminate enhancement of all that you learned. Analogous to looping your favorite songs in a repeating playlist at night, we cherry-pick specific slices of your autobiographical past, and preferentially strengthen them by using the individualized sound cues during sleep.

  37. Forgetting is the price we pay for remembering
  38. Brain can selectively identify specific memories that will be strengthened, and the ones forgotten
  39. The term “muscle memory” is a misnomer. Muscles themselves have no such memory: a muscle that is not connected to a brain cannot perform any skilled actions, nor does a muscle store skilled routines. Muscle memory is, in fact, brain memory. Training and strengthening muscles can help you better execute a skilled memory routine. But the routine itself—the memory program—resides firmly and exclusively within the brain.
  40. Practice makes perfect. Practice, with sleep, that makes perfect. Sleeping after practicing a new motoric skill (e.g. piano, guitar, riding a bicycle), you can expect a 20 percent jump in performance speed and a near 35 percent improvement in accuracy
  41. We are socially, organizationally, economically, physically, behaviorally, nutritionally, linguistically, cognitively, and emotionally dependent upon sleep
  42. Every hour, someone dies in a traffic accident in the US due to a fatigue-related error
  43. After the first night of no sleep at all, lapses in concentration (missed responses) increase by over 400 percent
  44. 10 days of 6 hours of sleep a night has the same effect as going without sleep for 24 hours straight.
  45. You do not know how sleep-deprived you are when sleep-deprived
  46. Millions of individuals unwittingly spend years of their life in a sub-optimal state of psychological and physiological functioning, never maximizing their potential of mind or body due to their blind persistence in sleeping too little
  47. Drowsy driving alone is worse than driving drunk. After being awake for nineteen hours, people who were sleep-deprived were as cognitively impaired as those who were legally drunk (.08 percent blood alcohol)
  48. The recycle rate of a human being is around sixteen hours (how long can a human go without sleep before their performance is objectively impaired)
  49. Humans need more than seven hours of sleep each night to maintain cognitive performance
  50. No matter what you may have heard or read in the popular media, there is no scientific evidence we have suggesting that a drug, a device, or any amount of psychological willpower can replace sleep.
  51. Without sleep, our brain reverts to a primitive pattern of uncontrolled reactivity. We produce unmetered, inappropriate emotional reactions, and are unable to place events into a broader or considered context
  52. Insufficient sleep does not push the brain into a negative mood state and hold it there. Rather, the under-slept brain swings excessively to both extremes of emotional valence, positive and negative
  53. Bipolar disorder
    1. Bipolar disorder

    2. Patients with bipolar depression vacillate between both ends of the emotion spectrum, experiencing dangerous periods of mania (excessive, reward-driven emotional behavior) and also periods of deep depression (negative moods and emotions). These extremes are often separated by a time when the patients are in a stable emotional state, neither manic nor depressed.
    3. A research team in Italy examined bipolar patients during the time when they were in this stable, inter-episode phase. Next, under careful clinical supervision, they sleep-deprived these individuals for one night. Almost immediately, a large proportion of the individuals either spiraled into a manic episode or became seriously depressed
  54. Major depression
    1. Major depression

    2. Patients suffering from major depression, in which they become exclusively locked into the negative end of the mood spectrum, show what at first appears to be a counterintuitive response to one night of sleep deprivation.
    3. Approximately 30 to 40 percent of these patients will feel better after a night without sleep. Their lack of slumber appears to be an antidepressant.
    4. The reason sleep deprivation is not a commonly used treatment, however, is twofold. First, as soon as these individuals do sleep, the antidepressant benefit goes away. Second, the 60 to 70 percent of patients who do not respond to the sleep deprivation will actually feel worse, deepening their depression. As a result, sleep deprivation is not a realistic or comprehensive therapy option
    5. Major depression has as much to do with absence of positive emotions, a feature described as anhedonia: the inability to gain pleasure from normally pleasurable experiences, such as food, socializing, or sex
    6. The one-third of depressed individuals who respond to sleep deprivation may therefore be those who experience the greater amplification within reward circuits of the brain resulting in far stronger sensitivity to, and experiencing of, positive rewarding triggers following sleep deprivation. Their anhedonia is therefore lessened, and now they can begin to experience a greater degree of pleasure from pleasurable life experiences
  55. E. Joseph Cossman: “The best bridge between despair and hope is a good night’s sleep.”
  56. Is pulling an all-nighter a wise idea for learning? — There was a 40 percent deficit in the ability of the sleep-deprived group to cram new facts into the brain (i.e., to make new memories), relative to the group that obtained a full night of sleep. To put that in context, it would be the difference between acing an exam and failing it miserably
  57. A night of sleep strengthens newly learned memories, boosting their retention
  58. Alzheimer's
    1. Alzheimer's disease

    2. Sleep disturbance precedes the onset of Alzheimer’s disease by several years, suggesting that it may be an early-warning sign of the condition, or even a contributor to it
    3. Over 60 percent of patients with Alzheimer’s disease have at least one clinical sleep disorder. Insomnia is especially common
    4. Alzheimer’s disease is associated with the buildup of a toxic form of protein called beta-amyloid, which aggregates in sticky clumps, or plaques, within the brain. Amyloid plaques are poisonous to neurons, killing the surrounding brain cells
    5. Amyloid plaques only affect some parts of the brain and not others. That area is the middle part of the frontal lobe—which is the same brain region essential for the electrical generation of deep NREM sleep in healthy young individuals. The more amyloid deposits there were in the middle regions of the frontal lobe, the more impaired the deep-sleep quality was in that older individual
    6. Despite Alzheimer’s disease being typified by memory loss, the hippocampus—that key memory reservoir in the brain—is mysteriously unaffected by amyloid protein
    7. Those individuals with the highest levels of amyloid deposits in the frontal regions of the brain had the most severe loss of deep sleep and, as a knock-on consequence, failed to successfully consolidate those new memories
    8. Glymphatic system. Sewage network called the glymphatic system exists within the brain. Glial cells are distributed throughout your entire brain, situated side by side with the neurons that generate the electrical impulses of your brain. Just as the lymphatic system drains contaminants from your body, the glymphatic system collects and removes dangerous metabolic contaminants generated by the hard work performed by neurons in your brain, rather like a support team surrounding an elite athlete. Although the glymphatic system—the support team—is somewhat active during the day, Nedergaard and her team discovered that it is during sleep that this neural sanitization work kicks into high gear. Associated with the pulsing rhythm of deep NREM sleep comes a ten- to twentyfold increase in effluent expulsion from the brain. In what can be described as a nighttime power cleanse, the purifying work of the glymphatic system is accomplished by cerebrospinal fluid that bathes the brain.
    9. The glial cells of the brain were shrinking in size by up to 60 percent during NREM sleep, enlarging the space around the neurons and allowing the cerebrospinal fluid to proficiently clean out the metabolic refuse left by the day’s neural activity. Think of the buildings of a large metropolitan city physically shrinking at night, allowing municipal cleaning crews easy access to pick up garbage strewn in the streets, followed by a good pressure-jet treatment of every nook and cranny. When we wake each morning, our brains can once again function efficiently thanks to this deep cleansing
    10. One piece of toxic debris evacuated by the glymphatic system during sleep is amyloid protein—the poisonous element associated with Alzheimer’s disease. Other dangerous metabolic waste elements that have links to Alzheimer’s disease are also removed by the cleaning process during sleep, including a protein called tau, as well as stress molecules produced by neurons when they combust energy and oxygen during the day
    11. Inadequate sleep and the pathology of Alzheimer’s disease interact in a vicious cycle. Without sufficient sleep, amyloid plaques build up in the brain, especially in deep-sleep generating regions, attacking and degrading them. The loss of deep NREM sleep caused by this assault therefore lessens the ability to remove amyloid from the brain at night, resulting in greater amyloid deposition. More amyloid, less deep sleep, less deep sleep, more amyloid, and so on and so forth
    12. 📌

      Getting too little sleep across the adult life span will significantly raise your risk of developing Alzheimer’s disease

    13. I have always found it curious that Margaret Thatcher and Ronald Reagan—two heads of state that were very vocal, if not proud, about sleeping only four to five hours a night—both went on to develop the ruthless disease
  59. Getting too little sleep across the adult life span will significantly raise your risk of developing Alzheimer’s disease
  60. For as long as the state of insufficient sleep lasts, and for some time thereafter, the body remains stuck in some degree of a fight-or-flight state
  61. During deep NREM sleep specifically, the brain communicates a calming signal to the fight-or-flight sympathetic branch of the body’s nervous system, and does so for long durations of the night. As a result, deep sleep prevents an escalation of this physiological stress that is synonymous with increased blood pressure, heart attack, heart failure, and stroke. This includes a calming effect on the contracting speed of your heart
  62. Daylight savings time. In the Northern Hemisphere, the switch to daylight savings time in March results in most people losing an hour of sleep opportunity. Should you tabulate millions of daily hospital records, as researchers have done, you discover that this seemingly trivial sleep reduction comes with a frightening spike in heart attacks the following day. Impressively, it works both ways. In the autumn within the Northern Hemisphere, when the clocks move forward and we gain an hour of sleep opportunity time, rates of heart attacks plummet the day after. A similar rise-and-fall relationship can be seen with the number of traffic accidents, proving that the brain, by way of attention lapses and microsleeps, is just as sensitive as the heart to very small perturbations of sleep. Most people think nothing of losing an hour of sleep for a single night, believing it to be trivial and inconsequential. It is anything but.
  63. The less you sleep, the more you are likely to eat
  64. Diabetes
    1. Diabetes

    2. Excessively high levels of blood sugar, or glucose, over weeks or years inflicts a surprising harm to the tissues and organs of your body, worsens your health, and shortens your life span
    3. In a healthy individual, the hormone insulin will trigger the cells of your body to swiftly absorb glucose from the bloodstream should it increase, as happens after eating a meal
    4. If the cells of your body stop responding to insulin, however, they cannot efficiently absorb glucose from the blood
    5. The research groups found far higher rates of type 2 diabetes among individuals that reported sleeping less than six hours a night routinely
    6. Participants were limited to sleeping four hours a night for just six nights. By the end of that week, these (formerly healthy) participants were 40 percent less effective at absorbing a standard dose of glucose, compared to when they were fully rested
    7. After participants had been restricted to four to five hours of sleep for a week, the cells of these tired individuals had become far less receptive to insulin. The cells were repelling rather than absorbing the dangerously high levels of glucose
  65. Two hormones controlling appetite: leptin and ghrelin. Leptin signals a sense of feeling full. When circulating levels of leptin are high, your appetite is blunted and you don’t feel like eating. Ghrelin, in contrast, triggers a strong sensation of hunger. When ghrelin levels increase, so, too, does your desire to eat. An imbalance of either one of these hormones can trigger increased eating and thus body weight
  66. A sleep-deprived body will cry famine in the midst of plenty
  67. When short sleeping, the very same individuals ate 300 calories more each day
  68. Three-year-olds sleeping just ten and a half hours or less have a 45 percent increased risk of being obese by age seven than those who get twelve hours of sleep a night
  69. When you are not getting enough sleep, the body becomes especially stingy about giving up fat. Instead, muscle mass is depleted while fat is retained
  70. Short sleep (of the type that many adults in first-world countries commonly and routinely report) will increase hunger and appetite, compromise impulse control within the brain, increase food consumption (especially of highcalorie foods), decrease feelings of food satisfaction after eating, and prevent effective weight loss when dieting.
  71. Reproductive hormones, reproductive organs, and the very nature of physical attractiveness that has a say in reproductive opportunities: all are degraded by short sleeping
  72. A single night of four hours of sleep—such as going to bed at three a.m. and waking up at seven a.m.—swept away 70 percent of the natural killer cells circulating in the immune system, relative to a full eight-hour night of sleep.
  73. Denmark recently became the first country to pay worker compensation to women who had developed breast cancer after years of night-shift work in government-sponsored jobs, such as nurses and air cabin crew
  74. The sleep-deprived mice suffered a 200 percent increase in the speed and size of cancer growth, relative to the well-rested group. The tumors were far more aggressive in the sleep-deficient animals. Their cancer had metastasized, spreading to surrounding organs, tissue, and bone
  75. Poor sleep quality therefore increases the risk of cancer development and, if cancer is established, provides a virulent fertilizer for its rapid and more rampant growth. Not getting sufficient sleep when fighting a battle against cancer can be likened to pouring gasoline on an already aggressive fire
  76. The emotional regions of the brain are up to 30 percent more active in REM sleep compared to when we are awake
  77. Between 35 and 55 percent of emotional themes and concerns that participants were having while they were awake during the day powerfully and unambiguously resurfaced in the dreams they were having at night
  78. Sleep, and specifically REM sleep, was clearly needed in order for us to heal emotional wounds
  79. It was only those patients who were expressly dreaming about the painful experiences around the time of the events who went on to gain clinical resolution from their despair, mentally recovering a year later as clinically determined by having no identifiable depression. Those who were dreaming, but not dreaming of the painful experience itself, could not get past the event, still being dragged down by a strong undercurrent of depression that remained.
  80. PTSD
    1. Solving PTSD

    2. Patients with PTSD, who are so often war veterans, have a difficult time recovering from horrific trauma experiences. They are frequently plagued by daytime flashbacks of these intrusive memories and suffer reoccurring nightmares. When a veteran soldier suffers a flashback triggered by, say, a car backfiring, they can relive the whole visceral traumatic experience again
    3. If the brain cannot divorce the emotion from memory across the first night following a trauma experience, the theory suggests that a repeat attempt of emotional memory stripping will occur on the second night, as the strength of the “emotional tag” associated with the memory remains too high. If the process fails a second time, the same attempt will continue to repeat the next night, and the next night, like a broken record. This was precisely what appeared to be happening with the recurring nightmares of the trauma experience in PTSD patients
    4. If I could lower the levels of noradrenaline in the brains of PTSD patients during sleep, thereby reinstating the right chemical conditions for sleep to do its trauma therapy work, then I should be able to restore healthier quality REM sleep. With that restored REM-sleep quality should come an improvement in the clinical symptoms of PTSD, and further, a decrease in the frequency of painful repetitive nightmares
    5. In his PTSD clinic, Raskind had been treating his war veteran patients with a generic drug called prazosin to manage their high blood pressure. While the drug was somewhat effective for lowering blood pressure in the body, Raskind found it had a far more powerful yet entirely unexpected benefit within the brain: it alleviated the reoccurring nightmares in his PTSD patients
    6. It turns out that the drug prazosin, which Raskind was prescribing simply to lower blood pressure, also has the fortuitous side effect of suppressing noradrenaline in the brain
  81. Problem-solving abilities rocketed up, with participants solving 15 to 35 percent more puzzles when emerging from REM sleep compared with awakenings from NREM sleep or during daytime waking performance
  82. It is sleep that builds connections between distantly related informational elements that are not obvious in the light of the waking day. Our participants went to bed with disparate pieces of the jigsaw and woke up with the puzzle complete. It is the difference between knowledge (retention of individual facts) and wisdom (knowing what they all mean when you fit them together). Or, said more simply, learning versus comprehension. REM sleep allows your brain to move beyond the former and truly grasp the latter
  83. REM sleep is capable of creating abstract overarching knowledge and super-ordinate concepts out of sets of information
  84. Sleepwalking
    1. Somnambulism (sleepwalking)

    2. The term “somnambulism” refers to sleep (somnus) disorders that involve some form of movement (ambulation). It encompasses conditions such as sleepwalking, sleep talking, sleep eating, sleep texting, sleep sex, and, very rarely, sleep homicide
    3. Most people believe these events happen during REM sleep as an individual is dreaming, and specifically acting out ongoing dreams. However, all these events arise from the deepest stage of non-dreaming (NREM) sleep, and not dream (REM) sleep.
    4. If you rouse an individual from a sleepwalking event and ask what was going through their mind, rarely will they report a thing—no dream scenario, no mental experience.
    5. An unexpected spike in nervous system activity during deep sleep is one trigger to sleepwalking. This electrical jolt compels the brain to rocket from the basement of deep NREM sleep all the way to the penthouse of wakefulness, but it gets stuck somewhere in between (the thirteenth floor, if you will). Trapped between the two worlds of deep sleep and wakefulness, the individual is confined to a state of mixed consciousness—neither awake nor asleep. In this confused condition, the brain performs basic but well-rehearsed actions, such as walking over to a closet and opening it, placing a glass of water to the lips, or uttering a few words or sentences
    6. Watching the video, the patient is clearly “awake” and behaving. But look at the brainwave activity and you realize that the patient, or at least their brain, is sound asleep. There are the clear and unmistakable slow electrical waves of deep NREM sleep, with no sign of fast, frenetic waking brainwave activity
    7. For the most part, there is nothing pathological about sleepwalking or sleep talking. They are common in the adult population, and even more common in children
    8. Most episodes of the condition are harmless. Occasionally, however, adult somnambulism can result in a much more extreme set of behaviors
    9. Story of Kenneth Parks in 1987
    10. Most somnambulism episodes (e.g., sleep walking, talking) are considered benign and do not require intervention
  85. Insomnia
    1. Insomnia

    2. Being sleep deprived is not insomnia
    3. In the field of medicine, sleep deprivation is considered as (i) having the adequate ability to sleep; yet (ii) giving oneself an inadequate opportunity to sleep—that is, sleep-deprived individuals can sleep, if only they would take the appropriate time to do so. Insomnia is the opposite: (i) suffering from an inadequate ability to generate sleep, despite (ii) allowing oneself the adequate opportunity to get sleep.
    4. People suffering from insomnia therefore cannot produce sufficient sleep quantity/quality, even though they give themselves enough time to do so (seven to nine hours).
    5. There are several different sub-types of insomnia
      1. The first is sleep onset insomnia, which is difficulty falling asleep
      2. The second is sleep maintenance insomnia, or difficulty staying asleep
    6. Sleep onset and sleep maintenance insomnia are not mutually exclusive: you can have one or the other, or both
    7. Clinical boxes to be checked to be considered a patient with insomnia:
    8. Dissatisfaction with sleep quantity or quality (e.g., difficulty falling asleep, staying sleep, early-morning awakening)
      Suffering significant distress or daytime impairment
      Has insomnia at least three nights each week for more than three months
      Does not have any coexisting mental disorders or medical conditions that could otherwise cause what appears to be insomnia
    9. Conclusion of symptoms: difficulty falling asleep, waking up in the middle of the night, waking up too early in the morning, difficulty falling back to sleep after waking up, and feeling unrefreshed throughout the waking day. If any of the characteristics of insomnia feel familiar to you, and have been present for several months, I suggest you consider seeking out a sleep medicine doctor
    10. The emphasis on duration of the sleep problem (more than three nights a week, for more than three months) is important.
    11. All of us will experience difficulty sleeping every now and then, which may last just one night or several. That is normal. There is usually an obvious cause, such as work stress or a flare-up in a social or romantic relationship. Once these things subside, though, the sleep difficulty usually goes away. Such acute sleep problems are generally not recognized as chronic insomnia, since clinical insomnia requires an ongoing duration of sleep difficulty, week after week after week
    12. Approximately one out of every nine people you pass on the street will meet the strict clinical criteria for insomnia
    13. Insomnia is almost twice as common in women than in men
    14. African Americans and Hispanic Americans suffering higher rates of insomnia than Caucasian Americans
    15. Should you relax the stringent clinical criteria and just use epidemiological data as a guide, it is probable that two out of every three people reading this book will regularly have difficulty falling or staying asleep at least one night a week, every week
    16. The “sleep aid” industry is worth an astonishing $30 billion a year in the US
    17. Insomnia shows some degree of genetic heritability, with estimates of 28 to 45 percent transmission rates from parent to child
    18. External factors that cause poor sleep, such as too much bright light at night, the wrong ambient room temperature, caffeine, tobacco, and alcohol consumption can masquerade as insomnia
    19. The two most common triggers of chronic insomnia are psychological: (1) emotional concerns, or worry, and (2) emotional distress, or anxiety.
    20. 📌

      In this fast-paced, information-overloaded modern world, one of the few times that we stop our persistent informational consumption and inwardly reflect is when our heads hit the pillow. There is no worse time to consciously do this. Little wonder that sleep becomes nearly impossible to initiate or maintain when the spinning cogs of our emotional minds start churning, anxiously worrying about things we did today, things that we forgot to do, things that we must face in the coming days, and even those far in the future. That is no kind of invitation for beckoning the calm brainwaves of sleep into your brain, peacefully allowing you to drift off into a full night of restful slumber

    21. The biological cause of insomnia is an overactive sympathetic nervous system, which is the body’s aggravating fight-or-flight mechanism. The physiological consequences are increased heart rate, blood flow, metabolic rate, the release of stress-negotiating chemicals such as cortisol, and increased brain activation, all of which are beneficial in the acute moment of true threat or danger.
    22. Health problems triggered by overactive sympathetic nervous system:
      1. The raised metabolic rate triggered by fight-or-flight nervous system activity, which is common in insomnia patients, results in a higher core body temperature
      2. Higher levels of the alertness-promoting hormone cortisol, and sister neurochemicals adrenaline and noradrenaline. All three of these chemicals raise heart rate
      3. Altered patterns of brain activity linked with the body’s sympathetic nervous system which prevent sleep from happening
      4. Patients with insomnia have a lower quality of sleep, reflected in shallower, less powerful electrical brainwaves during deep NREM. They also have more fragmented REM sleep, peppered by brief awakenings that they are not always aware of, yet still cause a degraded quality of dream sleep
    23. Simply put, the insomnia patients could not disengage from a pattern of altering, worrisome, ruminative brain activity. Think of a time when you closed the lid of a laptop to put it to sleep, but came back later to find that the screen was still on, the cooling fans were still running, and the computer was still active, despite the closed lid. Normally this is because programs and routines are still running, and the computer cannot make the transition into sleep mode.
    24. Recursive loops of emotional programs, together with retrospective and prospective memory loops, keep playing in the mind, preventing the brain from shutting down and switching into sleep mode
    25. Insomnia patients are unable to function well during the day, cognitively and/or emotionally. In this way, insomnia is really a 24/7 disorder: as much a disorder of the day as of the night.
    26. There is also paradoxical insomnia. Patients suffering from paradoxical insomnia therefore have an illusion, or misperception, of poor sleep that is not actually poor. As a result, such patients are treated as hypochondriacal
  86. The two most common triggers of chronic insomnia are psychological: (1) emotional concerns, or worry, and (2) emotional distress, or anxiety.
  87. In this fast-paced, information-overloaded modern world, one of the few times that we stop our persistent informational consumption and inwardly reflect is when our heads hit the pillow. There is no worse time to consciously do this. Little wonder that sleep becomes nearly impossible to initiate or maintain when the spinning cogs of our emotional minds start churning, anxiously worrying about things we did today, things that we forgot to do, things that we must face in the coming days, and even those far in the future. That is no kind of invitation for beckoning the calm brainwaves of sleep into your brain, peacefully allowing you to drift off into a full night of restful slumber
  88. Narcolepsy
    1. Narcolepsy

    2. Narcolepsy is considered to be a neurological disorder
    3. The condition usually emerges between ages ten and twenty years
    4. Three core symptoms that make up the disorder: (1) excessive daytime sleepiness, (2) sleep paralysis, and (3) cataplexy
    5. The daytime sleepiness is the equivalent of staying awake for three to four days straight.
    6. The second symptom of narcolepsy is sleep paralysis: the frightening loss of ability to talk or move when waking up from sleep. In essence, you become temporarily locked in your body
    7. Most of these events occur in REM sleep
    8. There can be rare occasions when the paralysis of the REM state lingers on despite the brain having terminated sleep. As a result, you begin to wake up, but you are unable to lift your eyelids, turn over, cry out, or move any of the muscles that control your limbs. Gradually, the paralysis of REM sleep does wear off, and you regain control of your body, including your eyelids, arms, legs, and mouth.
    9. Don’t worry if you have had an episode of sleep paralysis at some point in your life. It is not unique to narcolepsy. Around one in four healthy individuals will experience sleep paralysis, which is to say that it is as common as hiccups
    10. The third and most astonishing core symptom of narcolepsy is called cataplexy. The word comes from the Greek kata, meaning down, and plexis, meaning a stroke or seizure—that is, a falling-down seizure. However, a cataplectic attack is not a seizure at all, but rather a sudden loss of muscle control. This can range from slight weakness wherein the head droops, the face sags, the jaw drops, and speech becomes slurred to a buckling of knees or a sudden and immediate loss of all muscle tone, resulting in total collapse on the spot
    11. Cataplectic attacks are not random, but are triggered by moderate or strong emotions, positive or negative. Tell a funny joke to a narcoleptic patient, and they may literally collapse in front of you. Walk into a room and surprise a patient, perhaps while they are chopping food with a sharp knife, and they will collapse perilously. Even standing in a nice warm shower can be enough of a pleasurable experience to cause a patient’s legs to buckle and have a potentially dangerous fall caused by the cataplectic muscle loss.
    12. If you saw a patient collapse under the influence of cataplexy, you would be convinced that they had fallen completely unconscious or into a powerful sleep. This is untrue. Patients are awake and continue to perceive the outside world around them
    13. Scientists have examined the brains of narcoleptic patients in painstaking detail after they have passed away. During these postmortem investigations, they discovered a loss of almost 90 percent of all the cells that produce orexin. Worse still, the welcome sites, or receptors, of orexin that cover the surface of the power station of the brain stem were significantly reduced in number in narcoleptic patients, relative to normal individuals
    14. Because of this lack of orexin, made worse by the reduced number of receptor sites to receive what little orexin does drip down, the sleep-wake state of the narcoleptic brain is unstable, like a faulty flip-flop switch. Never definitively on or off, the brain of a narcoleptic patient wobbles precariously around a middle point, teeter-tottering between sleep and wakefulness
    15. Antidepressants are often prescribed to help with the second and third symptoms of narcolepsy—sleep paralysis and cataplexy—as they suppress REM sleep, and it is REM-sleep paralysis that is integral to these two symptoms. Nevertheless, antidepressants simply lower the incidence of both; they do not eradicate them.
  89. The problem is that some people confuse time slept with sleep opportunity time. We know that many individuals in the modern world only give themselves 5 to 6.5 hours of sleep opportunity, which normally means they will only obtain around 4.5 to 6 hours of actual sleep
  90. Modern society has taken one of nature’s perfect solutions (sleep) and neatly divided it into two problems: (1) a lack thereof at night, resulting in (2) an inability to remain fully awake during the day
  91. Artificial light in modern societies thus tricks us into believing night is still day, and does so using a physiological lie.
  92. Evening blue LED light has twice the harmful impact on nighttime melatonin suppression than the warm, yellow light from old incandescent bulbs, even when their lux intensities are matched
  93. One of the earliest studies found that using an iPad for two hours prior to bed blocked the otherwise rising levels of melatonin by a significant 23 percent
  94. Using LED devices at night impacts our natural sleep rhythms, the quality of our sleep, and how alert we feel during the day
  95. Sedation is not sleep. Alcohol sedates you out of wakefulness, but it does not induce natural sleep.
  96. Alcohol fragments sleep, littering the night with brief awakenings. Alcohol-infused sleep is therefore not continuous and, as a result, not restorative
  97. Thermal environment, specifically the proximal temperature around your body and brain, is perhaps the most underappreciated factor determining the ease with which you will fall asleep tonight, and the quality of sleep you will obtain
  98. Using the snooze feature means that you will repeatedly inflict that cardiovascular assault again and again within a short span of time
  99. Waking up at the same time of day, every day, no matter if it is the week or weekend is a good recommendation for maintaining a stable sleep schedule if you are having difficulty with sleep. Indeed, it is one of the most consistent and effective ways of helping people with insomnia get better sleep
  100. No past or current sleeping medications on the legal (or illegal) market induce natural sleep
  101. Individuals using prescription sleep medications are significantly more likely to die and to develop cancer than those who do not
  102. In younger, healthy adults, exercise frequently increases total sleep time, especially deep NREM sleep. It also deepens the quality of sleep, resulting in more powerful electrical brainwave activity
  103. 12 tips for healthy sleep
    1. ⭐12 tips for healthy sleep

    2. Stick to a sleep schedule. Go to bed and wake up at the same time each day. As creatures of habit, people have a hard time adjusting to changes in sleep patterns. Sleeping later on weekends won’t fully make up for a lack of sleep during the week and will make it harder to wake up early on Monday morning. Set an alarm for bedtime. Often we set an alarm for when it’s time to wake up but fail to do so for when it’s time to go to sleep. If there is only one piece of advice you remember and take from these twelve tips, this should be it.
    3. Exercise is great, but not too late in the day. Try to exercise at least thirty minutes on most days but not later than two to three hours before your bedtime.
    4. Avoid caffeine and nicotine. Coffee, colas, certain teas, and chocolate contain the stimulant caffeine, and its effects can take as long as eight hours to wear off fully. Therefore, a cup of coffee in the late afternoon can make it hard for you to fall asleep at night. Nicotine is also a stimulant, often causing smokers to sleep only very lightly. In addition, smokers often wake up too early in the morning because of nicotine withdrawal.
    5. Avoid alcoholic drinks before bed. Having a nightcap or alcoholic beverage before sleep may help you relax, but heavy use robs you of REM sleep, keeping you in the lighter stages of sleep. Heavy alcohol ingestion also may contribute to impairment in breathing at night. You also tend to wake up in the middle of the night when the effects of the alcohol have worn off.
    6. Avoid large meals and beverages late at night. A light snack is okay, but a large meal can cause indigestion, which interferes with sleep. Drinking too many fluids at night can cause frequent awakenings to urinate.
    7. If possible, avoid medicines that delay or disrupt your sleep. Some commonly prescribed heart, blood pressure, or asthma medications, as well as some over-the-counter and herbal remedies for coughs, colds, or allergies, can disrupt sleep patterns. If you have trouble sleeping, talk to your health care provider or pharmacist to see whether any drugs you’re taking might be contributing to your insomnia and ask whether they can be taken at other times during the day or early in the evening.
    8. Don’t take naps after 3 p.m. Naps can help make up for lost sleep, but late afternoon naps can make it harder to fall asleep at night.
    9. Relax before bed. Don’t overschedule your day so that no time is left for unwinding. A relaxing activity, such as reading or listening to music, should be part of your bedtime ritual.
    10. Take a hot bath before bed. The drop in body temperature after getting out of the bath may help you feel sleepy, and the bath can help you relax and slow down so you’re more ready to sleep.
    11. Dark bedroom, cool bedroom, gadget-free bedroom. Get rid of anything in your bedroom that might distract you from sleep, such as noises, bright lights, an uncomfortable bed, or warm temperatures. You sleep better if the temperature in the room is kept on the cool side. A TV, cell phone, or computer in the bedroom can be a distraction and deprive you of needed sleep. Having a comfortable mattress and pillow can help promote a good night’s sleep. Individuals who have insomnia often watch the clock. Turn the clock’s face out of view so you don’t worry about the time while trying to fall asleep.
    12. Have the right sunlight exposure. Daylight is key to regulating daily sleep patterns. Try to get outside in natural sunlight for at least thirty minutes each day. If possible, wake up with the sun or use very bright lights in the morning. Sleep experts recommend that, if you have problems falling asleep, you should get an hour of exposure to morning sunlight and turn down the lights before bedtime.
    13. Don’t lie in bed awake. If you find yourself still awake after staying in bed for more than twenty minutes or if you are starting to feel anxious or worried, get up and do some relaxing activity until you feel sleepy. The anxiety of not being able to sleep can make it harder to fall asleep.
  104. Certain business leaders mistakenly believe that time on-task equates with task completion and productivity
  105. A study across four large US companies found that insufficient sleep cost almost $2,000 per employee per year in lost productivity. That amount rose to over $3,500 per employee in those suffering the most serious lack of sleep
  106. Sleepy employees are unproductive employees
  107. Under-slept employees are not only less productive, less motivated, less creative, less happy, and lazier, but they are also more unethical
  108. Under-slept employees are more likely to blame other people in the workplace for their own mistakes, and even try to take credit for other people’s successful work
  109. We often think that a good or bad leader is good or bad day after day—a stable trait. Not true. Differences in individual leadership performance fluctuate dramatically from one day to the next, and the size of that difference far exceeds the average difference from one individual leader to another.
  110. In the days after a supervisor had slept poorly, the employees themselves, even if well rested, became less engaged in their jobs throughout that day as a consequence. It was a chain-reaction effect, one in which the lack of sleep in that one superordinate person in a business structure was transmitted on like a virus, infecting even wellrested employees with work disengagement and reduced productivity
  111. NASA discovered Naps as short as twenty-six minutes in length still offered a 34 percent improvement in task performance and more than a 50 percent increase in overall alertness. These results hatched the so-called NASA nap culture throughout terrestrial workers in the organization
  112. REM sleep is what stands between rationality and insanity. It is the lack of REM sleep—that critical stage occurring in the final hours of sleep that we strip from our children and teenagers by way of early school start times—that creates the difference between a stable and unstable mental state
  113. Over 70 percent of parents believing their child gets enough sleep, when in reality, less than 25 percent of children aged eleven to eighteen actually obtain the necessary amount
  114. When sleep is abundant, minds flourish. When it is deficient, they don’t
  115. ADHD
    1. Sleep deficiency and the epidemic of ADHD (attention deficit hyperactivity disorder)

    2. Children with this diagnosis are irritable, moodier, more distractible and unfocused in learning during the day, and have a significantly increased prevalence of depression and suicidal ideation.
    3. If you make a composite of these symptoms (unable to maintain focus and attention, deficient learning, behaviorally difficult, with mental health instability), and then strip away the label of ADHD, these symptoms are nearly identical to those caused by a lack of sleep.
    4. Take an under-slept child to a doctor and describe these symptoms without mentioning the lack of sleep, which is not uncommon, and what would you imagine the doctor is diagnosing the child with, and medicating them for? Not deficient sleep, but ADHD
    5. There is more irony here than meets the eye. Most people know the name of the common ADHD medications: Adderall and Ritalin. But few know what these drugs actually are. Adderall is amphetamine with certain salts mixed in, and Ritalin is a similar stimulant, called methylphenidate. Amphetamine and methylphenidate are two of the most powerful drugs we know of to prevent sleep and keep the brain of an adult (or a child, in this case) wide awake. That is the very last thing that such a child needs
    6. One example of an undiagnosed sleep disorder is pediatric sleep-disordered breathing, or child obstructive sleep apnea, which is associated with heavy snoring. Overly large adenoids and tonsils can block the airway passage of a child as their breathing muscles relax during sleep
    7. The resulting oxygen debt will reflexively force the brain to awaken the child briefly throughout the night so that several full breaths can be obtained, restoring full blood oxygen saturation. However, this prevents the child from reaching and/or sustaining long periods of valuable deep NREM sleep. Their sleep-disordered breathing will impose a state of chronic sleep deprivation, night after night, for months or years on end.
    8. As the state of chronic sleep deprivation builds over time, the child will look ever more ADHD-like in temperament, cognitively, emotionally, and academically
    9. Those children who are fortunate to have the sleep disorder recognized, and who have their tonsils removed, more often than not prove that they do not have ADHD. In the weeks after the operation, a child’s sleep recovers, and with it, normative psychological and mental functioning in the months ahead. Their “ADHD” is cured
    10. Based on recent surveys and clinical evaluations, we estimate that more than 50 percent of all children with an ADHD diagnosis actually have a sleep disorder, yet a small fraction know of their sleep condition and its ramifications
  116. Residents working a thirty-hour-straight shift will commit 36 percent more serious medical errors, such as prescribing the wrong dose of a drug or leaving a surgical implement inside of a patient, compared with those working sixteen hours or less.
  117. “I’ve always loathed the necessity of sleep. Like death, it puts even the most powerful men on their backs.” — Frank Underwood
  118. We receive 0 educational materials or information about sleep during our schooling years. Compared to information about diet, exercise, drugs, alcohol, and safe sex
  119. The return on the sleep investment in terms of productivity, creativity, work enthusiasm, energy, efficiency—not to mention happiness, leading to people wanting to work at your institution, and stay—is undeniable

🦅Key Principles

  1. Don't go on a diet without a normalized sleep schedule
  2. Your internal circadian rhythm clock maintains its timing regardless of whether you slept or not
  3. Melatonin doesn't generate sleep itself but only helps to regulate the timing of sleep
  4. Avoid frequent jet lags
  5. Don't drink coffee 5-7 hours before sleep
  6. Avoid nicotine for better sleep
  7. Avoid "caffeine crash." Don't drink multiple cups of coffee in a short time period.
  8. Both REM and NREM sleep cycles are equally important for your brain
  9. You can never “sleep back” that you have previously lost
  10. You sleep more sensitively in uncommon environments
  11. Do not schedule any important presentations or meetings in mid-afternoon hours
  12. Mid-afternoon naps are healthy and natural
  13. Do not deprive infant children of sleep
  14. Do not (let) consume alcohol during pregnancy
  15. Do not (let) consume alcohol during breastfeeding period
  16. Let your teenage children go to bed in late-night hours. Going to bed at 12-1AM is natural for teenagers
  17. If you want to go to sleep later and wake up later: exercise, get bright-light exposure in the late-afternoon, wear sunglasses during morning exercise, doze melatonine
  18. How to sleep safe for the elderly: have a side lamp, use motion-activated lights, remove obstacles, and keep a telephone by bed
  19. Sleep the night before learning
  20. Sleep the night after learning
  21. Rock the child's bed before sleeping
  22. Your mind doesn't understand how sleep-deprived it is when it's sleep-deprived
  23. Don't be awake for more than 16 hours. After sixteen hours of being awake, the brain begins to fail
  24. You will make 4x more mistakes after 24 hours without sleep
  25. After 10 days of just 7 hours of sleep, the brain is as dysfunctional as after 24 hours without sleep
  26. If you notice yourself feeling drowsy while driving, or actually falling asleep at the wheel, stop for the night
  27. Wait for 20-30 minutes after waking up before getting into high-concentration activity
  28. Take a short 40-120 minutes prophylactical power nap before a long day without sleep (24-36 hours)
  29. When you feel that you are staring at the page but nothing is going in, try again after getting some sleep
  30. When you are sleepy, you feel more hungry, more likely to eat bigger food portions, and more likely to eat junk food
  31. Don't let your woman to do late-night shift work
  32. Before thinking of making a baby, normalize your sleeping schedule
  33. When you are ill or sick, sleep
  34. Sleep to go past painful events. Dreams help to smoothen emotional reaction to painful events from the past. Dreams about the painful event itself are particularly effective to get past that event
  35. Dreams erase the emotional response related to the event, but they don't erase the memory of the event
  36. You are 3x times more effective in problem solving after having a full night of sleep
  37. Dreaming about the contents of the problem, will make you 10x times more effective in solving the problem
  38. You forget 50% of what you've learned if you drink alcohol in the next 3 days after studying
  39. Don't use digital devices with LED screens 2 hours before bed
  40. Create lowered, dim light in the rooms where you spend your evening hours
  41. Avoid powerful overhead lights
  42. Maintain complete darkness throughout the night
  43. De-saturate the blue LED light on your electronic devices
  44. Abstain from alcohol for better sleep
  45. Keep your bedroom temperature at around 18.3°C
  46. Keep your hands and feet warm in bed
  47. Take hot bath prior to bed
  48. Wake up at the same time, no matter if it is the week or weekend
  49. Don't use snooze feature on your alarm clock
  50. Go to bed only when sleepy
  51. Don't take sleeping pills
  52. Avoid sleeping on the couch early/mid-evenings
  53. Don’t lie in bed awake. If you find yourself still awake after staying in bed for more than twenty minutes or if you are starting to feel anxious or worried, get up and do some relaxing activity until you feel sleepy.
  54. Avoid daytime napping if you are having difficulty sleeping at night
  55. Relax before bed. Don’t overschedule your day so that no time is left for unwinding
  56. Remove visible clockfaces from view in the bedroom, preventing clock-watching anxiety at night
  57. Don't exercise within 2-3 hours before bed
  58. Avoid alcoholic drinks before bed
  59. Avoid large meals and beverages late at night
  60. Avoid medicines that delay or disrupt your sleep
  61. Don’t take naps after 3 p.m
  62. Get rid of anything in your bedroom that might distract you from sleep, such as noises, bright lights, an uncomfortable bed, or warm temperatures.
  63. Have the right sunlight exposure
  64. Avoid carbohydrate-rich diet (>70% of energy intake)
  65. Sleepy employees are unproductive employees
  66. The less you sleep, the less inspiring you will be as a leader. Your leadership skills vary from day to day
  67. By investing time in effective sleep, you solve work-related tasks faster and with less effort
  68. If you are about to undergo an elective surgery, you should ask how much sleep your doctor has had and, if it is not to your liking, you may not want to proceed.
  69. Track your sleep to analyze how it impacts your physical and mental health
  70. Integrate your sleep tracking device with smart home technology to control thermostat and lighting for better sleep

✍️Notes

Chapter 1: To Sleep

Quick facts about sleep

  • Two-thirds of adults throughout all developed nations fail to obtain the recommended eight hours of nightly sleep
  • Routinely sleeping less than six or seven hours a night demolishes your immune system, more than doubling your risk of cancer.
  • Insufficient sleep is a key lifestyle factor determining whether or not you will develop Alzheimer’s disease.
  • Inadequate sleep—even moderate reductions for just one week— disrupts blood sugar levels so profoundly that you would be classified as pre-diabetic
  • Should you attempt to diet but don’t get enough sleep while doing so, it is futile, since most of the weight you lose will come from lean body mass, not fat.
  • One person dies in a traffic accident every hour in the United States due to a fatigue-related error. It is disquieting to learn that vehicular accidents caused by drowsy driving exceed those caused by alcohol and drugs combined.
  • When we sleep less — we feel more hungry. It is because the hormone responsible for hunger goes out of balance and satiety hormone is suppressed
    • Too little sleep swells concentrations of a hormone that makes you feel hungry while suppressing a companion hormone that otherwise signals food satisfaction. Despite being full, you still want to eat more. It’s a proven recipe for weight gain in sleep-deficient adults and children alike.

Chapter 2: Caffeine, Jet Lag, and Melatonin: Losing and Gaining Control of Your Sleep Rhytm

What controls our sleep

There are two main factors that determine when you want to sleep and when you want to be awake. As you read these very words, both factors are powerfully influencing your mind and body. The first factor is a signal beamed out from your internal twenty-four-hour clock located deep within your brain. The clock creates a cycling, day-night rhythm that makes you feel tired or alert at regular times of night and day, respectively. The second factor is a chemical substance (adenosine) that builds up in your brain and creates a “sleep pressure.” The longer you’ve been awake, the more that chemical sleep pressure accumulates, and consequentially, the sleepier you feel. It is the balance between these two factors that dictates how alert and attentive you are during the day, when you will feel tired and ready for bed at night, and, in part, how well you will sleep.

  • Our sleep is driven by 2 main but independent factors: internal circadian rhythm and adenosine hormone (sleep pressure)
  • Described in this figure
    image

Circadian rhythm

  • Your twenty-four-hour tempo helps to determine when you want to be awake and when you want to be asleep. But it controls other rhythmic patterns, too. These include your timed preferences for eating and drinking, your moods and emotions, the amount of urine you produce, your core body temperature, your metabolic rate, and the release of numerous hormones
  • 📌

    The likelihood of breaking an Olympic record has been clearly tied to time of day, being maximal at the natural peak of the human circadian rhythm in the early afternoon

  • In complete darkness your body will still live by the ~24 hours cycle.
  • The cycle of Internal circadian human rhythm is slightly longer than the average day — 24 hours and 15 minutes.
  • Daylight is one of the main signals brain can catch in order to "reset" the cycle. So long as they are reliably repeating, the brain can also use other external cues, such as food, exercise, temperature fluctuations, and even regularly timed social interaction. All of these events have the ability to reset the biological clock, allowing it to strike a precise twenty-four-hour note. It is the reason that individuals with certain forms of blindness do not entirely lose their circadian rhythm
  • Body temperature fluctuates during the day. From 37.1C during peak activity hours (4PM), to 36.7C at night (12AM)
  • Figure
    image
  • Circadian clock doesn’t care if you slept or not — you will still be woken up based on your regular biorhythm.
  • 📌

    Wakefulness and sleep are under the control of the circadian rhythm, and not the other way around. That is, your circadian rhythm will march up and down every twenty-four hours irrespective of whether you have slept or not. Your circadian rhythm is unwavering in this regard

Morning larks and night owls

  • Although every human being displays an unyielding twenty-four-hour pattern, the respective peak and trough points are strikingly different from one individual to the next. For some people, their peak of wakefulness arrives early in the day, and their sleepiness trough arrives early at nigh
  • 3 types of people based on their activity rhytm
    • Morning types — 40% of population
    • Evening types — 30% of population
    • Mixed types — 30% of population
  • An adult’s owlness or larkness, also known as their chronotype, is strongly determined by genetics. If you are a night owl, it’s likely that one (or both) of your parents is a night owl
  • Society treats night owls unfairly
    • They are often labeled as being lazy, based on a night owl’s wont to wake up later in the day, due to the fact that they did not fall asleep until the early morning hours
    • Work scheduling is strongly biased toward early start times that punish owls and favor larks

Melatonin

  • The rise in melatonin begins soon after dusk
  • Melatonin acts like a powerful bullhorn, shouting out a clear message to the brain and body: “It’s dark, it’s dark!”
    • Melatonin does not control sleep itself. It only gives the signal to other parts of the body that now it's time to sleep, and the parts start triggering the sleep processes. It basically broadcasts the message "It's dark! It's dark!" to your whole body.
    • 📌

      Melatonin helps regulate the timing of when sleep occurs by systemically signaling darkness throughout the organism. But melatonin has little influence on the generation of sleep itself: a mistaken assumption that many people hold

  • Think of sleep as the Olympic 100-meter race. Melatonin is the voice of the timing official that says “Runners, on your mark,” and then fires the starting pistol that triggers the race. That timing official (melatonin) governs when the race (sleep) begins, but does not participate in the race. In this analogy, the sprinters themselves are other brain regions and processes that actively generate sleep
  • Scientific evaluations of over-the-counter brands have found melatonin concentrations that range from 83 percent less than that claimed on the label, to 478 percent more than that stated

Jet lags

  • This is jet lag: when traveling, you feel tired and sleepy during the day in the new time zone because your body clock and associated biology still “think” it is nighttime
  • It is easier to acclimatize to jet lags when traveling westward than eastward
    • The eastward direction requires that you fall asleep earlier than you would normally, which is a tall biological order for the mind to simply will into action. In contrast, the westward direction requires you to stay up later, which is a consciously and pragmatically easier prospect
    • Our natural circadian rhythm is innately longer than one day—about twenty-four hours and fifteen minutes. Modest as this may be, this makes it somewhat easier for you to artificially stretch a day than shrink it. When you travel westward—in the direction of your innately longer internal clock—that “day” is longer than twenty-four hours for you and why it feels a little easier to accommodate to
  • Jet lag places a torturous physiological strain on the brain, and deep biological stress upon the cells, organs, and major systems of the body. And there are consequences. Scientists have studied airplane cabin crews who frequently fly on long-haul routes and have little chance to recover. Two alarming results have emerged
    • First, parts of their brains— specifically those related to learning and memory—had physically shrunk, suggesting the destruction of brain cells caused by the biological stress of time-zone travel
    • Second, their short-term memory was significantly impaired

Sleep pressure (adenosine)

  • At this very moment, a chemical called adenosine is building up in your brain. It will continue to increase in concentration with every waking minute that elapses. The longer you are awake, the more adenosine will accumulate
  • As a result of the chemical sleep pressure of adenosine, you will have an irresistible urge to sleep. It happens to most people after twelve to sixteen hours of being awake

Caffeine

  • You can artificially mute the sleep signal of adenosine by using a chemical that makes you feel more alert and awake: caffeine
  • Caffeine is not a food supplement. Rather, caffeine is the most widely used (and abused) psychoactive stimulant in the world. It is the second most traded commodity on the planet, after oil. The consumption of caffeine represents one of the longest and largest unsupervised drug studies ever conducted on the human race, perhaps rivaled only by alcohol, and it continues to this day.
  • Caffeine blocks and effectively inactivates the receptors (adenosine welcome sites), acting as a masking agent. IBy hijacking and occupying these receptors, caffeine blocks the sleepiness signal normally communicated to the brain by adenosine.
  • 📌

    Caffeine tricks you into feeling alert and awake, despite the high levels of adenosine that would otherwise seduce you into sleep

  • Levels of circulating caffeine peak approximately thirty minutes after oral administration
  • Caffeine has an average half-life of five to seven hours. The time takes for the body to process 50% of caffeine portion intake is 5-7 hours.
  • Most people do not realize how long it takes to overcome a single dose of caffeine, and therefore fail to make the link between the bad night of sleep we wake from in the morning and the cup of coffee we had ten hours earlier with dinner
  • De-caffeinated does not mean non-caffeinated. One cup of decaf usually contains 15 to 30 percent of the dose of a regular cup of coffee, which is far from caffeine-free.
  • If you are trying to stay awake late into the night by drinking coffee, you should be prepared for a nasty consequence when your liver successfully evicts the caffeine from your system: a phenomenon commonly known as a “caffeine crash.” Like the batteries running down on a toy robot, your energy levels plummet rapidly. You find it difficult to function and concentrate, with a strong sense of sleepiness once again.
  • Caffeine is a deadly drug for your mind when consumed irresponsibly. See how spiders perform when given caffeine
  • Figure
    image

All-nighter

  • If you pull an all-nighter, you will feel disastrous at first, but the next day you catch the second wind during morning-afternoon hours. It is all due to your circadian rhythm. Eventually, you will want to sleep even more the second night after the sleep deprivation
  • image

Am I getting enough sleep?

  • Questions to ask yourself:
    • After waking up in the morning, could you fall back asleep at ten or eleven a.m.? If the answer is “yes,” you are likely not getting sufficient sleep quantity and/or quality.
    • Can you function optimally without caffeine before noon? If the answer is “no,” then you are most likely self-medicating your state of chronic sleep deprivation.
    • If you didn’t set an alarm clock, would you sleep past that time? (If so, you need more sleep than you are giving yourself.)
    • Do you find yourself at your computer screen reading and then rereading (and perhaps rereading again) the same sentence? (This is often a sign of a fatigued, under-slept brain.)
    • Do you sometimes forget what color the last few traffic lights were while driving? (Simple distraction is often the cause, but a lack of sleep is very much another culprit.)
  • Sleep debt accumulates. When you don’t get enough sleep, one consequence among many is that adenosine concentrations remain too high. Like an outstanding debt on a loan, come the morning, some quantity of yesterday’s adenosine remains. You then carry that outstanding sleepiness balance throughout the following day

Chapter 3: Defining and Generating Sleep

Self-identifying sleep

  • How to identify someone is sleeping?
    • Sleeping organisms adopt a stereotypical position. In land animals, this is often horizontal, as was Jessica’s position on the couch
    • Sleeping organisms have lowered muscle tone.
    • Sleeping individuals show no overt displays of communication or responsivity
    • Sleep is easily reversible, differentiating it from coma, anesthesia, hibernation, and death
    • Humans have a preference for being awake throughout the day and sleeping at night
  • How to identify you were sleeping?
    • Loss of external awareness—you stop perceiving the outside world
    • A sense of time distortion

Time distortion

  • Brain keeps track of time while you are sleeping. While your conscious mapping of time is lost during sleep, at a non-conscious level, time continues to be cataloged by the brain with incredible precision
    • Perhaps you had to catch an early-morning flight. Before bed, you diligently set your alarm for 6:00 a.m. Miraculously, however, you woke up at 5:58 a.m., unassisted, right before the alarm. Your brain, it seems, is still capable of logging time with quite remarkable precision while asleep. Like so many other operations occurring within the brain, you simply don’t have explicit access to this accurate time knowledge during sleep. It all flies below the radar of consciousness, surfacing only when needed
  • Time during dreams feels more stretched.
    • Consider the last time you hit the snooze button on your alarm, having been woken from a dream. Mercifully, you are giving yourself another delicious five minutes of sleep. You go right back to dreaming. After the allotted five minutes, your alarm clock faithfully sounds again, yet that’s not what it felt like to you. During those five minutes of actual time, you may have felt like you were dreaming for an hour, perhaps more

REM vs NREM sleep

  • Humans don’t just sleep, but cycle through two completely different types of sleep: NREM (non–rapid eye movement) and REM (rapid eye movement)
  • REM sleep, in which brain activity was almost identical to that when we are awake, was intimately connected to the experience we call dreaming, and is often described as dream sleep
  • NREM sleep is a deep sleep without any dreaming experience
  • NREM sleep is subdivided four separate stages, stages 1 to 4, increasing in their depth. Stages 3 and 4 are therefore the deepest stages of NREM sleep you experience, with “depth” being defined as the increasing difficulty required to wake an individual out of NREM stages 3 and 4, compared with NREM stages 1 or 2.

Sleep cycle

  • NREM and REM—play out in a recurring, push-pull battle for brain domination across the night
  • Average sleep experience is divided into 5 cycles
  • The duration of one cycle cycle is 90 minutes
  • 5 cycles have different proportions of REM and NREM sleep in them. With Cycle 5 having the most REM sleep, and Cycle 1 having the least.
  • Figure
    image
  • The early phases after you fall asleep are rich with deep NREM sleep. The phases before you wake up are rich with dream-rich REM sleep
  • Back-and-forth interplay between NREM and REM sleep is necessary to elegantly remodel and update our neural circuits at night, and in doing so manage the finite storage space within the brain. Forced by the known storage capacity imposed by a set number of neurons and connections within their memory structures, our brains must find the “sweet spot” between retention of old information and leaving sufficient room for the new
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    The key function of deep NREM sleep, which predominates early in the night, is to do the work of weeding out and removing unnecessary neural connections. In contrast, the dreaming stage of REM sleep, which prevails later in the night, plays a role in strengthening those connections

  • Let’s say that you go to bed this evening at midnight. But instead of waking up at eight a.m., getting a full eight hours of sleep, you must wake up at six a.m. because of an early-morning meeting or because you are an athlete whose coach demands early-morning practices. What percent of sleep will you lose? The logical answer is 25 percent, since waking up at six a.m. will lop off two hours of sleep from what would otherwise be a normal eight hours. But that’s not entirely true. Since your brain desires most of its REM sleep in the last part of the night, which is to say the late morning hours, you will lose 60 to 90 percent of all your REM sleep, even though you are losing 25 percent of your total sleep time. It works both ways. If you wake up at eight a.m., but don’t go to bed until two a.m., then you lose a significant amount of deep NREM sleep. Similar to an unbalanced diet in which you only eat carbohydrates and are left malnourished by the absence of protein, short-changing the brain of either NREM or REM sleep—both of which serve critical, though different, brain and body functions—results in a myriad of physical and mental ill health, as we will see in later chapters. When it comes to sleep, there is no such thing as burning the candle at both ends—or even at one end—and getting away with it.

Which type of sleep is more important?

Which type of sleep—NREM or REM sleep—is more important? Which do we really need?

There are many ways you can define “importance” or “need,” and thus numerous ways of answering the question. But perhaps the simplest recipe is to take an organism that has both sleep types, bird or mammal, and keep it awake all night and throughout the subsequent day. NREM and REM sleep are thus similarly removed, creating the conditions of equivalent hunger for each sleep stage. The question is, which type of sleep will the brain feast on when you offer it the chance to consume both during a recovery night? NREM and REM sleep in equal proportions? Or more of one than the other, suggesting greater importance of the sleep stage that dominates?

This experiment has now been performed many times on numerous species of birds and mammals, humans included. There are two clear outcomes. First, and of little surprise, sleep duration is far longer on the recovery night (ten or even twelve hours in humans) than during a standard night without prior deprivation (eight hours for us). Responding to the debt, we are essentially trying to “sleep it off,” the technical term for which is a sleep rebound.

Second, NREM sleep rebounds harder. The brain will consume a far larger portion of deep NREM sleep than of REM sleep on the first night after total sleep deprivation, expressing a lopsided hunger. Despite both sleep types being on offer at the finger buffet of recovery sleep, the brain opts to heap much more deep NREM sleep onto its plate. In the battle of importance, NREM sleep therefore wins. Or does it?

Not quite. Should you keep recording sleep across a second, third, and even fourth recovery night, there’s a reversal. Now REM sleep becomes the primary dish of choice with each returning visit to the recovery buffet table, with a side of NREM sleep added. Both sleep stages are therefore essential. We try to recover one (NREM) a little sooner than the other (REM), but make no mistake, the brain will attempt to recoup both, trying to salvage some of the losses incurred. It is important to note, however, that regardless of the amount of recovery opportunity, the brain never comes close to getting back all the sleep it has lost. This is true for total sleep time, just as it is for NREM sleep and for REM sleep

Brainwaves of sleep

Figure of brainwaves of wake and sleep
image

  • REM sleep brainwaves have almost identical structure to those of awake state
  • REM sleep brainwaves are chaotic and don't have a specific pattern
  • Deep NREM sleep brainwaves have a predictable pattern
  • During NREM sleep, multiple clusters of braincells unite and produce signals simultaneously
  • What you are actually experiencing during deep NREM sleep is one of the most epic displays of neural collaboration that we know of. Through an astonishing act of self-organization, many thousands of brain cells have all decided to unite and “sing,” or fire, in time

Brain as an information processing system

  • The steady, slow, synchronous waves that sweep across the brain during deep sleep open up communication possibilities between distant regions of the brain, allowing them to collaboratively send and receive their different repositories of stored experience
  • You can think of each individual slow wave of NREM sleep as a courier, able to carry packets of information between different anatomical brain centers. One benefit of these traveling deep-sleep brainwaves is a file-transfer process. Each night, the long-range brainwaves of deep sleep will move memory packets (recent experiences) from a short-term storage site, which is fragile, to a more permanent, and thus safer, long-term storage location. We therefore consider waking brainwave activity as that principally concerned with the reception of the outside sensory world, while the state of deep NREM slow-wave sleep donates a state of inward reflection—one that fosters information transfer and the distillation of memories.
  • Wake state = reception. Experiencing and constantly learning the world around you
  • NREM sleep = reflection. Storing and strengthening those raw ingredients of new facts and skills
  • REM sleep = integration. Interconnecting these raw ingredients with each other, with all past experiences, and, in doing so, building an ever more accurate model of how the world works, including innovative insights and problem-solving abilities

REM sleep paralysis

  • Mere seconds before the dreaming phase begins, and for as long as that REM-sleep period lasts, you are completely paralyzed
  • Why did evolution decide to outlaw muscle activity during REM sleep? Because by eliminating muscle activity you are prevented from acting out your dream experience. During REM sleep, there is a nonstop barrage of motor commands swirling around the brain, and they underlie the movement-rich experience of dreams. Wise, then, of Mother Nature to have tailored a physiological straitjacket that forbids these fictional movements from becoming reality, especially considering that you’ve stopped consciously perceiving your surroundings. You can well imagine the calamitous upshot of falsely enacting a dream fight, or a frantic sprint from an approaching dream foe, while your eyes are closed and you have no comprehension of the world around you. It wouldn’t take long before you quickly left the gene pool.
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    The brain paralyzes the body so the mind can dream safely

Chapter 4 - Ape Beds, Dinosaurs, and Napping with Half a Brain

Who sleeps?

  • Without exception, every animal species studied to date sleeps, or engages in something remarkably like it. This includes insects, such as flies, bees, cockroaches, and scorpions; fish, from small perch to the largest sharks; amphibians, such as frogs; and reptiles, such as turtles, Komodo dragons, and chameleons

Sleep difference 1 — Duration

  • Total amount of time is one of the most conspicuous differences in how organisms sleep
  • Elephants need half as much sleep as humans, requiring just four hours of slumber each day. Tigers and lions devour fifteen hours of daily sleep. The brown bat outperforms all other mammals, being awake for just five hours each day while sleeping nineteen hours
  • For now, our most accurate estimate of why different species need different sleep amounts involves a complex hybrid of factors, such as dietary type (omnivore, herbivore, carnivore), predator/prey balance within a habitat, the presence and nature of a social network, metabolic rate, and nervous system complexity

Sleep difference 2 — Composition

  • Another remarkable difference in sleep across species is composition
  • Every species in which we can measure sleep stages experiences NREM sleep—the non-dreaming stage. However, insects, amphibians, fish, and most reptiles show no clear signs of REM sleep—the type associated with dreaming in humans. Only birds and mammals, which appeared later in the evolutionary timeline of the animal kingdom, have full-blown REM sleep
  • Dream (REM) sleep is the new kid on the evolutionary block. REM sleep seems to have emerged to support functions that NREM sleep alone could not accomplish, or that REM sleep was more efficient at accomplishing
  • REM sleep may have been birthed twice in the course of evolution: once for birds and once for mammals

Sleep difference 3 — Means

  • A third striking difference in sleep across the animal kingdom is the way in which we all do it
  • Dolphins and whales can sleep with only half a brain at a time
  • Birds can do it, too. However, there is a somewhat different, though equally life-preserving, reason: it allows them to keep an eye on things, quite literally. When birds are alone, one half of the brain and its corresponding (opposite-side) eye must stay awake, maintaining vigilance to environmental threats. As it does so, the other eye closes, allowing its corresponding half of the brain to sleep.
  • Sleep with both sides of the brain, or sleep with just one side and then switch. Both are possible, but sleep you must. Sleep is non-negotiable
  • We sleep more sensitively in uncommon environments. If you compare the electrical depth of the deep NREM slow brainwaves on one half of someone’s head relative to the other when they are sleeping at home, they are about the same. But if you bring that person into a sleep laboratory, or take them to a hotel—both of which are unfamiliar sleep environments—one half of the brain sleeps a little lighter than the other, as if it’s standing guard with just a tad more vigilance due to the potentially less safe context that the conscious brain has registered while awake. The more nights an individual sleeps in the new location, the more similar the sleep is in each half of the brain. It is perhaps the reason why so many of us sleep so poorly the first night in a hotel room

Sleep difference 4 — Flexibility

  • The fourth and final difference in sleep across the animal kingdom is the way in which sleep patterns can be diminished under rare and very special circumstances
  • Individuals who are deliberately fasting will sleep less as the brain is tricked into thinking that food has suddenly become scarce
  • In-flight, migrating birds will grab remarkably brief periods of sleep lasting only seconds in duration. These ultra–power naps are just sufficient to avert the ruinous brain and body deficits that would otherwise ensue from prolonged total sleep deprivation
  • The white-crowned sparrow has an unparalleled, though time-limited, resilience to total sleep deprivation, one that we humans could never withstand. If you sleep-deprive this sparrow in the laboratory during the migratory period of the year (when it would otherwise be in flight), it suffers virtually no ill effects whatsoever. However, depriving the same sparrow of the same amount of sleep outside this migratory time window inflicts a maelstrom of brain and body dysfunction

How should we sleep?

  • Throughout developed nations, most adults currently sleep in a monophasic pattern—that is, we try to take a long, single bout of slumber at night, the average duration of which is now less than seven hours
  • Hunter-gatherer tribes, such as the Gabra in northern Kenya or the San people in the Kalahari Desert, whose way of life has changed little over the past thousands of years, sleep in a biphasic pattern. Both these groups take a similarly longer sleep period at night (seven to eight hours of time in bed, achieving about seven hours of sleep), followed by a thirty- to sixty-minute nap in the afternoon
  • The practice of biphasic sleep is not cultural in origin, however. It is deeply biological. All humans, irrespective of culture or geographical location, have a genetically hardwired dip in alertness that occurs in the midafternoon hours.
  • Observe any post-lunch meeting around a boardroom table and this fact will become evidently clear. Like puppets whose control strings were let loose, then rapidly pulled taut, heads will start dipping then quickly snap back upright. I’m sure you’ve experienced this blanket of drowsiness that seems to take hold of you, midafternoon, as though your brain is heading toward an unusually early bedtime. Both you and the meeting attendees are falling prey to an evolutionarily imprinted lull in wakefulness that favors an afternoon nap, called the post-prandial alertness dip (from the Latin prandium, “meal”). This brief descent from high-degree wakefulness to low-level alertness reflects an innate drive to be asleep and napping in the afternoon, and not working. It appears to be a normal part of the daily rhythm of life
  • 📌

    You experience a state of drowsiness and lack of alertness during midafternoon hours because humans were programmed to take short 30-60 minute naps during that time

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The true pattern of biphasic sleep—for which there is anthropological, biological, and genetic evidence, and which remains measurable in all human beings to date—is one consisting of a longer bout of continuous sleep at night, followed by a shorter midafternoon nap.

Humans are special — role of rich REM sleep

  • Between 20 and 25 percent of our sleep time is dedicated to REM sleep dreaming, compared to an average of only 9 percent across all other primates!
  • It all began when humans transitioned from sleeping on the trees to sleeping on the ground
  • When sleeping on the ground, there’s no more risk of falling. For the first time in our evolution, hominids could consume all the body immobilized REM-sleep dreaming they wanted, and not worry about the lasso of gravity whipping them down from treetops. Our sleep therefore became “concentrated”: shorter and more consolidated in duration, packed aplenty with high-quality sleep
  • The tree-to-ground reengineering of sleep was a key trigger that rocketed Homo sapiens to the top of evolution’s lofty pyramid. At least two features define human beings relative to other primates. I posit that both have been beneficially and causally shaped by the hand of sleep, and specifically our intense degree of REM sleep relative to all other mammals: (1) our degree of sociocultural complexity, and (2) our cognitive intelligence. REM sleep, and the act of dreaming itself, lubricates both of these human traits.
  • REM sleep may very well have accelerated the richness and rational control of our initially primitive emotions
  • REM sleep increases our ability to recognize and therefore successfully navigate the kaleidoscope of socioemotional signals that are abundant in human culture, such as overt and covert facial expressions, major and minor bodily gestures, and even mass group behavior.
  • The coolheaded ability to regulate our emotions each day—a key to what we call emotional IQ—depends on getting sufficient REM sleep night after night
  • REM-sleep dreaming state fuels creativity. NREM sleep helps transfer and make safe newly learned information into long-term storage sites of the brain. But it is REM sleep that takes these freshly minted memories and begins colliding them with the entire back catalog of your life’s autobiography. These mnemonic collisions during REM sleep spark new creative insights as novel links are forged between unrelated pieces of information. Sleep cycle by sleep cycle, REM sleep helps construct vast associative networks of information within the brain. REM sleep can even take a step back, so to speak, and divine overarching insights and gist: something akin to general knowledge—that is, what a collection of information means as a whole, not just an inert back catalogue of facts. We can awake the next morning with new solutions to previously intractable problems or even be infused with radically new and original ideas
  • Nevertheless, the superior emotional brain gifts that REM sleep affords should be considered more influential in defining our hominid success than the second benefit, of inspiring creativity. Creativity is an evolutionarily powerful tool, yes. But it is largely limited to an individual
  • Now we can appreciate what I believe to be a classic, self-fulfilling positive cycle of evolution. Our shift from tree to ground sleeping instigated an ever more bountiful amount of relative REM sleep compared with other primates, and from this bounty emerged a steep increase in cognitive creativity, emotional intelligence, and thus social complexity. This, alongside our increasingly dense, interconnected brains, led to improved daily (and nightly) survival strategies. In turn, the harder we worked those increasingly developed emotional and creative circuits of the brain during the day, the greater was our need to service and recalibrate these ever-demanding neural systems at night with more REM sleep.

Chapter 5: Changes in Sleep Across the Life Span

Before birth

  • Prior to birth, a human infant will spend almost all of its time in a sleep-like state, much of which resembles the REM-sleep state. The sleeping fetus is therefore unaware of its parents’ performative machinations. Any co-occurring arm flicks and leg bops that the mother feels from her baby are most likely to be the consequence of random bursts of brain activity that typify REM sleep
  • The twenty-four-hour period contains a mishmash of approximately six hours of NREM sleep, six hours of REM sleep, and twelve hours of an intermediary sleep state
  • In the last two weeks of pregnancy, the fetus will ramp up its consumption of REM sleep to almost nine hours a day
  • In the last week before birth, REM-sleep amount hits a lifetime high of twelve hours a day
  • Dazzling bursts of electrical activity during REM sleep stimulate the lush growth of neural pathways all over the developing brain, and then furnish each with a healthy bouquet of connecting ends, or synaptic terminals
  • REM sleep is essential for the brain formation process. The time of life when REM sleep is greatest is the same stage when the brain is undergoing the greatest construction
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Every hour of REM sleep appears to count, as evidenced by the desperate attempt by a fetus or newborn to regain any REM sleep when it is lost. Blocking or reducing REM sleep in newborn animals hinders and distorts brain development, leading to an adult that is socially abnormal

Autism and sleep

  • If you disturb or impair the REM sleep of a developing infant brain, pre- or early post-term, and there are consequences
  • A more recent link with deficient REM sleep concerns autism spectrum disorder (ASD). Infants and young children who show signs of autism, or who are diagnosed with autism, do not have normal sleep patterns or amounts.
  • The circadian rhythms of autistic children are also weaker than their non-autistic counterparts, showing a flatter profile of melatonin across the twenty-four-hour period rather than a powerful rise in concentration at night and rapid fall throughout the day. It is as if the day and night are far less light and dark, respectively, for autistic individuals
  • Most notable, however, is the significant shortage of REM sleep. Autistic individuals show a 30 to 50 percent deficit in the amount of REM sleep they obtain, relative to children without autism
  • Rats deprived of REM sleep during infancy go on to become socially withdrawn and isolated as adolescents and adults

Alcohol and pregnant mothers

  • Alcohol is one of the most powerful suppressors of REM sleep that we know of
  • Alcohol consumed by a mother readily crosses the placental barrier, and therefore readily infuses her developing fetus
  • The newborns of heavy-drinking mothers spent far less time in the active state of REM sleep compared with infants of similar age but who were born of mothers who did not drink during pregnancy
  • Newborns of heavy-drinking mothers did not have the same electrical quality of REM sleep. The infants of heavy-drinking mothers showed a 200 percent reduction in this measure of vibrant electrical activity relative to the infants born of non-alcohol-consuming mothers
  • Does one glass of wine matter? Participants of the experiment — pregnant women drank approximately two glasses of wine. Alcohol significantly reduced the amount of time that the unborn babies spent in REM sleep, relative to the non-alcohol condition. That alcohol also dampened the intensity of REM sleep experienced by the fetus, defined by the standard measure of how many darting rapid eye movements adorn the REM-sleep cycle. Furthermore, these unborn infants suffered a marked depression in breathing during REM sleep, with breath rates dropping from a normal rate of 381 per hour during natural sleep to just 4 per hour when the fetus was awash with alcohol

Alcohol and breastfeeding

  • Almost half of all lactating women in Western countries consume alcohol in the months during breastfeeding.
  • Alcohol is readily absorbed in a mother’s milk.
  • Concentrations of alcohol in breast milk closely resemble those in a mother’s bloodstream: a 0.08 blood alcohol level in a mother will result in approximately a 0.08 alcohol level in breast milk
  • Newborns will normally transition straight into REM sleep after a feeding
  • When babies consume alcohol-laced milk, their sleep is more fragmented, they spend more time awake, and they suffer a 20 to 30 percent suppression of REM sleep soon after

Childhood sleep

  • In contrast to the single, monophasic sleep pattern observed in adults of industrialized nations, infants and young kids display polyphasic sleep: many short snippets of sleep through the day and night, punctuated by numerous awakenings, often vocal.
  • The older a child gets, the fewer, longer, and more stable their sleep bouts become
  • Not until age three or four months will a newborn show modest signs of being governed by a daily rhythm
  • By the one-year milestone of development, the suprachiasmatic nucleus clock of an infant has gripped the steering reins of the circadian rhythm. This means that the child now spends more of the day awake, interspersed with several naps and, mercifully, more of the night asleep
  • By four years of age, the circadian rhythm is in dominant command of a child’s sleep behavior, with a lengthy slab of nighttime sleep, usually supplemented by just a single daytime nap
  • During the fourteen hours of total shut-eye per day that a six-month-old infant obtains, there is a 50/50 timeshare between NREM and REM sleep
  • A five-year-old, however, will have a 70/30 split between NREM and REM sleep across the eleven hours of total daily slumber
  • The proportion of REM sleep decreases in early childhood while the proportion of NREM sleep actually increases, even though total sleep time decreases
  • That balance will finally stabilize to an 80/20 NREM/REM sleep split by the late teen years, and remain so throughout early and midadulthood.

Sleep and adolescence

  • A decline in REM-sleep intensity in the first year of life, yet an exponential rise in deep NREM sleep intensity in mid- and late childhood, hitting a peak just before puberty, and then damping back down
  • REM sleep plays an essential role in this proliferation process, helping to populate brain neighborhoods with neural connectivity, and then activate those pathways with a healthy dose of informational bandwidth
  • But since this first round of brain wiring is purposefully overzealous, a second round of remodeling must take place. It does so during late childhood and adolescence. Here, the architectural goal is not to scale up, but to scale back for the goal of efficiency and effectiveness. The time of adding brain connections with the help of REM sleep is over. Instead, pruning of connections becomes the order of the day or, should I say, night. Enter the sculpting hand of deep NREM sleep
  • A (somewhat) generic brain becomes ever more individualized, based on the personalized use of the owner
  • Adolescents have a less rational version of an adult brain, one that takes more risks and has relatively poor decision-making skills
  • As deep NREM sleep performs its final overhaul and refinement of the brain during adolescence, cognitive skills, reasoning, and critical thinking start to improve, and do so in a proportional manner with that NREM sleep change
  • The changes in deep NREM sleep always precede the cognitive and developmental milestones within the brain by several weeks or months, implying a direction of influence: deep sleep may be a driving force of brain maturation, not the other way around.
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Deep NREM sleep helps in preparing brain for the adulthood

  • Rationality is one of the last things to flourish in teenagers, as it is the last brain territory to receive sleep’s maturational treatment
  • Many of the major psychiatric disorders, such as schizophrenia, bipolar disorder, major depression, and ADHD are now considered disorders of abnormal development, since they commonly emerge during childhood and adolescence.
  • In young individuals who are at high risk of developing schizophrenia, and in teenagers and young adults with schizophrenia, there is a two- to threefold reduction in deep NREM sleep

Circadian rhythm shift in teenagers

  • Adolescents face two other harmful challenges in their struggle to obtain sufficient sleep as their brains continue to develop. The first is a change in their circadian rhythm. The second is early school start times
  • Children become sleepy earlier and wake up earlier than their adult parents due to their circadian rhythm running on an earlier schedule
  • Adolescent teenagers, however, have a different circadian rhythm from their young siblings. During puberty, the timing of the suprachiasmatic nucleus is shifted progressively forward: a change that is common across all adolescents, irrespective of culture or geography. So far forward, in fact, it passes even the timing of their adult parents.
  • As a nine-year-old, the circadian rhythm would have the child asleep by around nine p.m., driven in part by the rising tide of melatonin at this time in children. The sixteen-year-old will usually have no interest in sleeping at nine p.m. Instead, peak wakefulness is usually still in play at that hour
  • By the time the parents are getting tired, as their circadian rhythms take a downturn and melatonin release instructs sleep—perhaps around ten or eleven p.m., their teenager can still be wide awake. A few more hours must pass before the circadian rhythm of a teenage brain begins to shut down alertness and allow for easy, sound sleep to begin.
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Asking your teenage son or daughter to go to bed and fall asleep at ten p.m. is the circadian equivalent of asking you, their parent, to go to sleep at seven or eight p.m. No matter how loud you enunciate the order, no matter how much that teenager truly wishes to obey your instruction, and no matter what amount of willed effort is applied by either of the two parties, the circadian rhythm of a teenager will not be miraculously coaxed into a change. Furthermore, asking that same teenager to wake up at seven the next morning and function with intellect, grace, and good mood is the equivalent of asking you, their parent, to do the same at four or five a.m.

  • It will not always be this way for the teenager. As they age into young and middle adulthood, their circadian schedule will gradually slide back in time

Sleep in midlife and old age

  • Sleep is more problematic and disordered in older adults
  • Older adults appear to need just as much sleep as they do in midlife, but are simply less able to generate that (still necessary) sleep
  • The decline of deep NREM sleep is already underway by your late twenties and early thirties
  • As you enter your fourth decade of life, there is a palpable reduction in the electrical quantity and quality of that deep NREM sleep. You obtain fewer hours of deep sleep, and those deep NREM brainwaves become smaller, less powerful, and fewer in number
  • Passing into your mid- and late forties, age will have stripped you of 60 to 70 percent of the deep sleep you were enjoying as a young teenager.
  • By the time you reach seventy years old, you will have lost 80 to 90 percent of your youthful deep sleep.
  • Elderly individuals fail to connect their deterioration in health with their deterioration in sleep. Seniors therefore complain about and seek treatment for their health issues when visiting their GP, but rarely ask for help with their equally problematic sleep issues. As a result, GPs are rarely motivated to address the problematic sleep in addition to the problematic health concerns of the older adult.
  • The older we get, the more frequently we wake up throughout the night. There are many causes, including interacting medications and diseases, but chief among them is a weakened bladder. Older adults therefore visit the bathroom more frequently at night. Reducing fluid intake in the mid- and late evening can help, but it is not a cure-all
  • As healthy teenagers, we enjoyed a sleep efficiency of about 95 percent. As a reference anchor, most sleep doctors consider good-quality sleep to involve a sleep efficiency of 90 percent or above. By the time we reach our eighties, sleep efficiency has often dropped below 70 or 80 percent
  • The nighttime bathroom visits and associated risk of falls and thus fractures. We are often groggy when we wake up during the night. Add to this cognitive haze the fact that it is dark. Furthermore, having been recumbent in bed means that when you stand and start moving, blood can race from your head, encouraged by gravity, down toward your legs. You feel light headed and unsteady on your feet as a consequence. The latter is especially true in older adults whose control of blood pressure is itself often impaired. All of these issues mean that an older individual is at a far higher risk of stumbling, falling, and breaking bones during nighttime visits to the bathroom
  • Tips for safe sleep in the elderly:
    • Have a side lamp within reach that you can switch on easily
    • Use dim or motion-activated night-lights in the bathrooms and hallways to illuminate your path
    • Remove obstacles or rugs en route to the bathroom to prevent stumbles or trips
    • Keep a telephone by your bed with emergency phone numbers programmed on speed dial
  • In sharp contrast to adolescents, seniors commonly experience a regression in sleep timing, leading to earlier and earlier bedtimes
  • The strengths of the circadian rhythm and amount of nighttime melatonin released also decrease the older we get
  • There are methods that can help push the circadian rhythm in older adults somewhat later, and also strengthen the rhythm
    • Exercise can help solidify good sleep, especially in the elderly
    • Older adults who want to shift their bedtimes to a later hour should get bright-light exposure in the late-afternoon hours
    • Wear sunglasses during morning exercise outdoors. This will reduce the influence of morning light being sent to your suprachiasmatic clock that would otherwise keep you on an early-to-rise schedule.
    • Go back outside in the late afternoon for sunlight exposure, but this time do not wear sunglasses. Make sure to wear sun protection of some sort, such as a hat, but leave the sunglasses at home. Plentiful later-afternoon daylight will help delay the evening release of melatonin, helping push the timing of sleep to a later hour.
    • Unlike young or middle-age adults, where melatonin has not proved efficacious for helping sleep beyond the circumstance of jet lag, prescription melatonin has been shown to help boost the otherwise blunted circadian and associated melatonin rhythm in the elderly, reducing the time taken to fall asleep and improving self-reported sleep quality and morning alertness
  • What is it about the aging process that so thoroughly robs the brain of this essential state of slumber?
    • The areas of the brain that suffer the most dramatic deterioration with aging are, unfortunately, the very same deep-sleep-generating regions—the middle-frontal regions seated above the bridge of the nose
    • Older adults suffered a 70 percent loss of deep sleep, compared with matched young individuals
    • These changes were not independent, but instead significantly connected with one another: the more severe the deterioration that an older adult suffers within this specific mid-frontal region of their brain, the more dramatic their loss of deep NREM sleep
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The parts of our brain that ignite healthy deep sleep at night are the very same areas that degenerate, or atrophy, earliest and most severely as we age

  • Older adults with the greatest loss of deep sleep showed the most catastrophic overnight forgetting. Poor memory and poor sleep in old age are therefore not coincidental, but rather significantly interrelated
  • Poor sleep is one of the most underappreciated factors contributing to cognitive and medical ill health in the elderly, including issues of diabetes, depression, chronic pain, stroke, cardiovascular disease, and Alzheimer’s disease
  • Older adults, may, in fact, need more sleep than they themselves can naturally generate, since they benefit from an improvement in sleep quality, albeit through artificial means

Part 2: Why Should We Sleep?

Chapter 6: The Benefits of Sleep for the Brain

Sleep is not the absence of wakefulness. It is far more than that

Each stage of sleep—light NREM sleep, deep NREM sleep, and REM sleep—offer different brain benefits at different times of night. Thus, no one type of sleep is more essential than another. Losing out on any one of these types of sleep will cause brain impairment.

Sleep for learning

  • Sleep has proven itself time and again as a memory aid: both before learning, to prepare your brain for initially making new memories, and after learning, to cement those memories and prevent forgetting.

Sleep the night before learning

  • Sleep before learning refreshes our ability to initially make new memories
  • A long, finger-shaped structure tucked deep on either side of your brain, the hippocampus offers a short-term reservoir, or temporary information store, for accumulating new memories. Unfortunately, the hippocampus has a limited storage capacity, almost like a camera roll or, to use a more modern-day analogy, a USB memory stick. Exceed its capacity and you run the risk of not being able to add more information or, equally bad, overwriting one memory with another: a mishap called interference forgetting
  • People who take a nap between morning and evening learning sessions, remember 20% more than those who don't
  • The memory refreshment was related to lighter, stage 2 NREM sleep, and specifically the short, powerful bursts of electrical activity called sleep spindles. The more sleep spindles an individual obtained during the nap, the greater the restoration of their learning when they woke up
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During sleep, memories transition from short-term storage (hippocampus) to long-term storage site (cortex)

  • The more sleep spindles an individual has at night, the greater the restoration of overnight learning ability come the next morning
  • Sleep six hours or less and you are shortchanging the brain of a learning restoration benefit that is normally performed by sleep spindles

Sleep the night after learning

  • The second benefit of sleep for memory comes after learning, one that effectively clicks the “save” button on those newly created files. In doing so, sleep protects newly acquired information, affording immunity against forgetting: an operation called consolidation
  • Memory retention benefit of between 20 and 40 percent being offered by sleep, compared to the same amount of time awake.
  • Which sleep period would confer a greater memory savings benefit—that filled with deep NREM, or that packed with abundant REM sleep? — For fact-based, textbook-like memory, the early-night sleep, rich in deep NREM, wins out in terms of providing superior memory retention savings relative to late-night, REM-rich sleep
  • The more deep NREM sleep, the more information an individual remembered the next day
  • Before having slept, participants were fetching memories from the short-term storage site of the hippocampus. After the full night of sleep, participants were now retrieving that same information from the neocortex
  • Even daytime naps as short as twenty minutes can offer a memory consolidation advantage, so long as they contain enough NREM sleep

Memory enhancements

  • You can enhance your memory retention during sleep by using sleep stimulation, and targeted memory reactivation
Experiment 1: Enhancing brainwaves using electrical stimulation

Since sleep is expressed in patterns of electrical brainwave activity, sleep stimulation approaches began by trading in the same currency: electricity. In 2006, a research team in Germany recruited a group of healthy young adults for a pioneering study in which they applied electrode pads onto the head, front and back. Rather than recording the electrical brainwaves being emitted from the brain during sleep, the scientists did the opposite: inserted small amounts of electrical voltage. They patiently waited until each participant had entered into the deepest stages of NREM sleep and, at that point, switched on the brain stimulator, pulsing in rhythmic time with the slow waves. The electrical pulsations were so small that participants did not feel them, nor did they wake up. But they had a measurable impact on sleep. Both the size of the slow brainwaves and the number of sleep spindles riding on top of the deep brainwaves were increased by the stimulation, relative to a control group of subjects who did not receive stimulation during sleep. Before being put to bed, all the participants had learned a list of new facts. They were tested the next morning after sleep. By boosting the electrical quality of deep-sleep brainwave activity, the researchers almost doubled the number of facts that individuals were able to recall the following day, relative to those participants who received no stimulation. Applying stimulation during REM sleep, or during wakefulness across the day, did not offer similar memory advantages. Only stimulation during NREM sleep, in synchronous time with the brain’s own slow mantra rhythm, leveraged a memory improvement.

  • It is possible to achieve nearly 100 percent memory enhancement the next morning using proper electrical stimulation during NREM sleep.
Experiment 2: Enhancing memory retention using audiowaves

Other methods for amplifying the brainwaves of sleep are fast being developed. One technology involves quiet auditory tones being played over speakers next to the sleeper. Like a metronome in rhythmic stride with the individual slow waves, the tick-tock tones are precisely synchronized with the individual’s sleeping brainwaves to help entrain their rhythm and produce even deeper sleep. Relative to a control group that slept but had no synchronous auditory chimes at night, the auditory stimulation increased the power of the slow brainwaves and returned an impressive 40 percent memory enhancement the next morning.

  • It is possible to achieve 40 percent memory enhancement the next morning using sound stimulation during NREM sleep.
  • Slow rocking increased the depth of deep sleep, boosted the quality of slow brainwaves, and more than doubled the number of sleep spindles
Experiment 3: Targeted memory reactivation

Before going to sleep, we show participants individual pictures of objects at different spatial locations on a computer screen, such as a cat in the lower right side, or a bell in the upper center, or a kettle near the top right of the screen. As a participant, you have to remember not only the individual items you have been shown, but also their spatial location on the screen. You will be shown a hundred of these items. After sleep, picture objects will again appear on the screen, now in the center, some of which you have seen before, some you have not. You have to decide if you remember the picture object or not, and if you do, you must move that picture object to the spatial location on the screen where it originally appeared, using a mouse. In this way, we can assess whether you remember the object, and also how accurately you can remember its location. But here is the intriguing twist. As you were originally learning the images before sleep, each time an object was presented on the screen, a corresponding sound was played. For example, you would hear “meow” when the cat picture was shown, or “ding-a-ling” when the bell was shown. All picture objects are paired, or “auditory-tagged,” with a semantically matching sound. When you are asleep, and in NREM sleep specifically, an experimenter will replay half of the previously tagged sounds (fifty of the total hundred) to your sleeping brain at low volume using speakers on either side of the bed. As if helping guide the brain in a targeted search-and-retrieve effort, we can trigger the selective reactivation of corresponding individual memories, prioritizing them for sleep-strengthening, relative to those that were not reactivated during NREM sleep. When you are tested the following morning, you will have a quite remarkable bias in your recollection, remembering far more of the items that we reactivated during sleep using the sound cues than those not reactivated. Note that all one hundred of the original memory items passed through sleep. However, using sound cuing, we avoid indiscriminate enhancement of all that you learned. Analogous to looping your favorite songs in a repeating playlist at night, we cherry-pick specific slices of your autobiographical past, and preferentially strengthen them by using the individualized sound cues during sleep.

Sleep to forget

  • The capacity to forget can, in certain contexts, be as important as the need for remembering
  • Forgetting is not just beneficial to delete stored information we no longer need. It also lowers the brain resources required for retrieving those memories we want to retain, similar to the ease of finding important documents on a neatly organized, clutter-free desk
  • 📌

    Forgetting is the price we pay for remembering

Experiment: "R" - remember and "F" - forget

We designed an experiment that again used daytime naps. At midday, our research subjects studied a long list of words presented one at a time on a computer screen. After each word had been presented on the screen, however, a large green “R” or a large red “F” was displayed, indicating to the participant that they should remember the prior word (R) or forget the prior word (F). It is not dissimilar to being in a class and, after having been told a fact, the teacher impresses upon you that it is especially important to remember that information for the exam, or instead that they made an error and the fact was incorrect, or the fact will not be tested on the exam, so you don’t need to worry about remembering it for the test. We were effectively doing the same thing for each word right after learning, tagging it with the label “to be remembered” or “to be forgotten.” Half of the participants were then allowed a ninety-minute afternoon nap, while the other half remained awake. At six p.m. we tested everyone’s memory for all of the words. We told participants that regardless of the tag previously associated with a word—to be remembered or to be forgotten—they should try to recall as many words as possible. Our question was this: Does sleep improve the retention of all words equally, or does sleep obey the waking command only to remember some items while forgetting others, based on the tags we had connected to each? The results were clear. Sleep powerfully, yet very selectively, boosted the retention of those words previously tagged for “remembering,” yet actively avoided the strengthening of those memories tagged for “forgetting.” Participants who did not sleep showed no such impressive parsing and differential saving of the memories

  • Brain can selectively identify specific memories that will be strengthened, and the ones forgotten
    • Counter to earlier assumptions in the twentieth and twenty-first centuries, sleep does not offer a general, nonspecific (and hence verbose) preservation of all the information you learn during the day. Instead, sleep is able to offer a far more discerning hand in memory improvement: one that preferentially picks and chooses what information is, and is not, ultimately strengthened. Sleep accomplishes this by using meaningful tags that have been hung onto those memories during initial learning, or potentially identified during sleep itself
    • Exactly how sleep spindles accomplish this clever memory trick remains unclear. What we have at least discovered is a rather telling pattern of looping activity in the brain that coincides with these speedy sleep spindles. The activity circles between the memory storage site (the hippocampus) and those regions that program the decision of intentionality (in the frontal lobe), such as “This is important” or “This is irrelevant.” The recursive cycle of activity between these two areas (memory and intentionality), which happens ten to fifteen times per second during the spindles, may help explain NREM sleep’s discerning memory influence

Sleep for motoric skills memory

  • The term “muscle memory” is a misnomer. Muscles themselves have no such memory: a muscle that is not connected to a brain cannot perform any skilled actions, nor does a muscle store skilled routines. Muscle memory is, in fact, brain memory. Training and strengthening muscles can help you better execute a skilled memory routine. But the routine itself—the memory program—resides firmly and exclusively within the brain.

Practice makes perfect. Practice, with sleep, that makes perfect

Experiment: 4-1-3-2-4 keyboard memory

I took a large group of right-handed individuals and had them learn to type a number sequence on a keyboard with their left hand, such as 4-1-3-2-4, as quickly and as accurately as possible. Like learning a piano scale, subjects practiced the motor skill sequence over and over again, for a total of twelve minutes, taking short breaks throughout. Unsurprisingly, the participants improved in their performance across the training session; practice, after all, is supposed to make perfect. We then tested the participants twelve hours later. Half of the participants had learned the sequence in the morning and were tested later that evening after remaining awake across the day. The other half of the subjects learned the sequence in the evening and we retested them the next morning after a similar twelve-hour delay, but one that contained a full eight-hour night of sleep. Those who remained awake across the day showed no evidence of a significant improvement in performance. However, fitting with the pianist’s original description, those who were tested after the very same time delay of twelve hours, but that spanned a night of sleep, showed a striking 20 percent jump in performance speed and a near 35 percent improvement in accuracy. Importantly, those participants who learned the motor skill in the morning—and who showed no improvement that evening—did go on to show an identical bump up in performance when retested after a further twelve hours, now after they, too, had had a full night’s sleep

Analyzing the individual elements of the motor sequence, such as 4-1-3-2-4, allowed me to discover how, precisely, sleep was perfecting skill. Even after a long period of initial training, participants would consistently struggle with particular transitions within the sequence. These problem points stuck out like a sore thumb when I looked at the speed of the keystrokes. There would be a far longer pause, or consistent error, at specific transitions. For example, rather than seamlessly typing 4-1-3-2-4, 4-1-3-2-4, a participant would instead type: 4-1-3 [pause] 2-4, 4-1-3 [pause] 2-4. They were chunking the motor routine into pieces, as if attempting the sequences all in one go was just too much. Different people had different pause problems at different points in the routine, but almost all people had one or two of these difficulties. I assessed so many participants that I could actually tell where their unique difficulties in the motor routine were just by listening to their typing during training. When I tested participants after a night of sleep, however, my ears heard something very different. I knew what was happening even before I analyzed the data: mastery. Their typing, postsleep, was now fluid and unbroken. Gone was the staccato performance, replaced by seamless automaticity, which is the ultimate goal of motor learning: 4-1-3-2-4, 4-1-3-2-4, 4-1-3-2-4, rapid and nearly perfect. Sleep had systematically identified where the difficult transitions were in the motor memory and smoothed them out. This finding rekindled the words of the pianist I’d met: “but when I wake up the next morning and sit back down at the piano, I can just play, perfectly.”

  • Sleeping after practicing a new motoric skill (e.g. piano, guitar, riding a bicycle), you can expect a 20 percent jump in performance speed and a near 35 percent improvement in accuracy
  • Your brain will continue to improve skill memories in the absence of any further practice
  • The increases in speed and accuracy, underpinned by efficient automaticity, were directly related to the amount of stage 2 NREM, especially in the last two hours of an eight-hour night of sleep (e.g., from five to seven a.m., should you have fallen asleep at eleven p.m.)
  • Numerous studies have shown that sleep improves the motor skills of junior, amateur, and elite athletes across sports as diverse as tennis, basketball, football, soccer, and rowing
  • Obtain anything less than eight hours of sleep a night, and especially less than six hours a night, and the following happens: time to physical exhaustion drops by 10 to 30 percent, and aerobic output is significantly reduced. Similar impairments are observed in limb extension force and vertical jump height, together with decreases in peak and sustained muscle strength. Add to this marked impairments in cardiovascular, metabolic, and respiratory capabilities that hamper an underslept body, including faster rates of lactic acid buildup, reductions in blood oxygen saturation, and converse increases in blood carbon dioxide, due in part to a reduction in the amount of air that the lungs can expire. Even the ability of the body to cool itself during physical exertion through sweating—a critical part of peak performance —is impaired by sleep loss
  • Lack of sleep causes a risk of injuries in sports
  • Figure
    image
  • >8 hour sleep vs <8 hour sleep NBA player performance
  • Figure
    image

Sleep for creativity

  • A final benefit of sleep for memory is arguably the most remarkable of all: creativity. Sleep provides a nighttime theater in which your brain tests out and builds connections between vast stores of information. This task is accomplished using a bizarre algorithm that is biased toward seeking out the most distant, nonobvious associations, rather like a backward Google search. In ways your waking brain would never attempt, the sleeping brain fuses together disparate sets of knowledge that foster impressive problem-solving abilities. If you ponder the type of conscious experience such outlandish memory blending would produce, you may not be surprised to learn that it happens during the dreaming state—REM sleep

Chapter 7: Sleep Deprivation and the Brain

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The Guinness Book of World Records has stopped recognizing attempts to break the sleep deprivation world record

We are socially, organizationally, economically, physically, behaviorally, nutritionally, linguistically, cognitively, and emotionally dependent upon sleep

Attention

  • One brain function that buckles under even the smallest dose of sleep deprivation is concentration
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Every hour, someone dies in a traffic accident in the US due to a fatigue-related error

  • The most common cause is a momentary lapse in concentration, called a microsleep. These last for just a few seconds, during which time the eyelid will either partially or fully close. They are usually suffered by individuals who are chronically sleep restricted, defined as getting less than seven hours of sleep a night on a routine basis
  • During a microsleep, your brain becomes blind to the outside world for a brief moment—and not just the visual domain, but in all channels of perception
  • Slowness is not the most sensitive signature of sleepiness, entirely missed responses were. Sleep-deprived experiment participants would, for brief moments, stop responding altogether.
  • After the first night of no sleep at all, lapses in concentration (missed responses) increase by over 400 percent. These impairments continue to escalate at the same ballistic rate after a second and third night of total sleep deprivation
  • After four hours of sleep for six nights, participants’ performance was just as bad as those who had not slept for twenty-four hours straight—that is, a 400 percent increase in the number of microsleeps. By day 11 on this diet of four hours of sleep a night, participants’ performance had degraded even further, matching that of someone who had pulled two back-to-back all-nighters, going without sleep for forty-eight hours
  • 10 days of 6 hours of sleep a night has the same effect as going without sleep for 24 hours straight.
  • All signs suggested that if the experiment had continued, the performance deterioration would continue to build up over weeks or months

Subjective understanding of sleep deprivation

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You do not know how sleep-deprived you are when sleep-deprived

  • When participants were asked about their subjective sense of how impaired they were, they consistently underestimated their degree of performance disability. It is the equivalent of someone at a bar who has had far too many drinks picking up his car keys and confidently telling you, “I’m fine to drive home.”
  • With chronic sleep restriction over months or years, an individual will actually acclimate to their impaired performance, lower alertness, and reduced energy levels
  • Millions of individuals unwittingly spend years of their life in a sub-optimal state of psychological and physiological functioning, never maximizing their potential of mind or body due to their blind persistence in sleeping too little
  • After three nights of ad-lib recovery sleep, performance did not return to that observed at the original baseline assessment when those same individuals had been getting a full eight hours of sleep regularly

Drowsy driving

  • After being awake for nineteen hours, people who were sleep-deprived were as cognitively impaired as those who were legally drunk (.08 percent blood alcohol)
  • The relationship between decreasing hours of sleep and increasing mortality risk of an accident is not linear, but instead exponentially mushrooms. Each hour of sleep lost vastly amplifies that crash likelihood, rather than incrementally nudging it up
  • Figure
    image
  • Those in the 4-hour sleep condition had six times more off-road deviations than the sober, well-rested individuals. The same result as for the group with eight hours of sleep but legally drunk
  • Four hours of sleep plus the effect of alcohol group of participants drove off the road almost thirty times more than the well-rested, sober group
  • The heady cocktail of sleep loss and alcohol was not additive, but instead multiplicative
  • This coming week, more than 2 million people in the US will fall asleep while driving their motor vehicle. That’s more than 250,000 every day, with more such events during the week than weekends for obvious reasons.
  • More than 56 million Americans admit to struggling to stay awake at the wheel of a car each month
  • 1.2 million accidents are caused by sleepiness each year in the United States
  • Drowsy driving alone is worse than driving drunk. Vehicle accidents caused by drowsy driving exceed those caused by alcohol and drugs combined.
  • Truck Drivers. Approximately 80 percent of truck drivers in the US are overweight, and 50 percent are clinically obese. This places truck drivers at a far, far higher risk of a disorder called sleep apnea, commonly associated with heavy snoring, which causes chronic, severe sleep deprivation. As a result, these truck drivers are 200 to 500 percent more likely to be involved in a traffic accident. And when a truck driver loses his or her life in a drowsy-driving crash, they will, on average, take 4.5 other lives with them
  • Many of us think we can overcome drowsiness through sheer force of will, but, sadly, this is not true
  • If you notice yourself feeling drowsy while driving, or actually falling asleep at the wheel, stop for the night. If you really must keep going—and you have made that judgment in the life-threatening context it genuinely poses—then pull off the road into a safe layby for a short time. Take a brief nap (twenty to thirty minutes). When you wake up, do not start driving. You will be suffering from sleep inertia—the carryover effects of sleep into wakefulness. Wait for another twenty to thirty minutes, perhaps after having a cup of coffee if you really must, and only then start driving again. This, however, will only get you so far down the road before you need another such recharge, and the returns are diminishing. Ultimately, it is just not worth the (life) cost
  • Common myths that are of no use in helping to overcome drowsiness while driving include: turning up the radio, winding down the car window, blowing cold air on your face, splashing cold water on your face, talking on the phone, chewing gum, slapping yourself, pinching yourself, punching yourself, and promising yourself a reward forstaying awake.

Summary of facts

  • The recycle rate of a human being is around sixteen hours (how long can a human go without sleep before their performance is objectively impaired)
  • After sixteen hours of being awake, the brain begins to fail
  • Humans need more than seven hours of sleep each night to maintain cognitive performance
  • After ten days of just seven hours of sleep, the brain is as dysfunctional as it would be after going without sleep for twenty-four hours
  • Three full nights of recovery sleep (i.e., more nights than a weekend) are insufficient to restore performance back to normal levels after a week of short sleeping
  • The human mind cannot accurately sense how sleep-deprived it is when sleep-deprived.

Power naps

  • 68 percent of all catastrophic plane crashes occur during the end phase of flight, known in the aviation industry as “top of descent to landing,” when the greatest amount of sleep deprivation has often accrued
  • If a pilot can only obtain a short nap opportunity (40–120 minutes) within a thirty-six-hour period, when should it occur so as to minimize cognitive fatigue and attention lapses: at the start of the first evening, in the middle of the night, or late the following morning?
    • It first appeared to be counterintuitive, but Dinges and Rosekind made a clever, biology-based prediction. They believed that by inserting a nap at the front end of an incoming bout of sleep deprivation, you could insert a buffer, albeit temporary and partial, that would protect the brain from suffering catastrophic lapses in concentration. They were right. Pilots suffered fewer microsleeps at the end stages of the flight if the naps were taken early that prior evening, versus if those same nap periods were taken in the middle of the night or later that next morning, when the attack of sleep deprivation was already well under way
    • These short sleep bouts, taken early, also reduced the number of times the pilots drifted into light sleep during the critical, final ninety minutes of flight
  • No matter what you may have heard or read in the popular media, there is no scientific evidence we have suggesting that a drug, a device, or any amount of psychological willpower can replace sleep.
  • Power naps may momentarily increase basic concentration under conditions of sleep deprivation, as can caffeine up to a certain dose. Neither naps nor caffeine can salvage more complex functions of the brain, including learning, memory, emotional stability, complex reasoning, or decision-making.

Sleepless elite

  • We have, however, discovered a very rare collection of individuals who appear to be able to survive on six hours of sleep, and show minimal impairment—a sleepless elite, as it were
  • Part of the explanation appears to lie in their genetics, specifically a sub-variant of a gene called BHLHE41
  • The gene is remarkably rare, with but a soupçon of individuals in the world estimated to carry this anomaly. It is far, far more likely that you will be struck by lightning (the lifetime odds being 1 in 12,000) than being truly capable of surviving on insufficient sleep thanks to a rare gene

Emotional irrationality

  • Bad sleep the night before leads to a bad mood and emotional reactivity the next day
  • A structure located in the left and right sides of the brain, called the amygdala—a key hot spot for triggering strong emotions such as anger and rage, and linked to the fight-or-flight response— showed well over a 60 percent amplification in emotional reactivity in the participants who were sleep-deprived
  • Without sleep, our brain reverts to a primitive pattern of uncontrolled reactivity. We produce unmetered, inappropriate emotional reactions, and are unable to place events into a broader or considered context
  • With a full night of plentiful sleep, we have a balanced mix between our emotional gas pedal (amygdala) and brake (prefrontal cortex). Without sleep, however, the strong coupling between these two brain regions is lost. We cannot rein in our atavistic impulses—too much emotional gas pedal (amygdala) and not enough regulatory brake (prefrontal cortex)
  • No matter how you take sleep from the brain—acutely, across an entire night, or chronically, by short sleeping for a handful of nights —the emotional brain consequences are the same
  • Insufficient sleep does not push the brain into a negative mood state and hold it there. Rather, the under-slept brain swings excessively to both extremes of emotional valence, positive and negative
  • Insufficient sleep during childhood significantly predicts early onset of drug and alcohol use in that same child during their later adolescent years, even when controlling for other high-risk traits, such as anxiety, attention deficits, and parental history of drug use

Psychiatric diseases

  • Healthy people can experience a neurological pattern of brain activity similar to that observed in many of these psychiatric conditions simply by having their sleep disrupted or blocked
  • Sleep disruption remains a neglected factor contributing to the instigation and/or maintenance of numerous psychiatric illnesses
  • Should you improve sleep quality in patients suffering from several psychiatric conditions, you can improve symptom severity and remission rates

Bipolar disorder

  • Patients with bipolar depression vacillate between both ends of the emotion spectrum, experiencing dangerous periods of mania (excessive, reward-driven emotional behavior) and also periods of deep depression (negative moods and emotions). These extremes are often separated by a time when the patients are in a stable emotional state, neither manic nor depressed.
  • A research team in Italy examined bipolar patients during the time when they were in this stable, inter-episode phase. Next, under careful clinical supervision, they sleep-deprived these individuals for one night. Almost immediately, a large proportion of the individuals either spiraled into a manic episode or became seriously depressed

Major depression

  • Patients suffering from major depression, in which they become exclusively locked into the negative end of the mood spectrum, show what at first appears to be a counterintuitive response to one night of sleep deprivation.
  • Approximately 30 to 40 percent of these patients will feel better after a night without sleep. Their lack of slumber appears to be an antidepressant.
  • The reason sleep deprivation is not a commonly used treatment, however, is twofold. First, as soon as these individuals do sleep, the antidepressant benefit goes away. Second, the 60 to 70 percent of patients who do not respond to the sleep deprivation will actually feel worse, deepening their depression. As a result, sleep deprivation is not a realistic or comprehensive therapy option
  • Major depression has as much to do with absence of positive emotions, a feature described as anhedonia: the inability to gain pleasure from normally pleasurable experiences, such as food, socializing, or sex
  • The one-third of depressed individuals who respond to sleep deprivation may therefore be those who experience the greater amplification within reward circuits of the brain resulting in far stronger sensitivity to, and experiencing of, positive rewarding triggers following sleep deprivation. Their anhedonia is therefore lessened, and now they can begin to experience a greater degree of pleasure from pleasurable life experiences
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E. Joseph Cossman: “The best bridge between despair and hope is a good night’s sleep.”

Sleep and preparing for an exam

  • Is pulling an all-nighter a wise idea for learning? — There was a 40 percent deficit in the ability of the sleep-deprived group to cram new facts into the brain (i.e., to make new memories), relative to the group that obtained a full night of sleep. To put that in context, it would be the difference between acing an exam and failing it miserably
  • There was lots of healthy, learning-related activity in the hippocampus in the participants who had slept the night before. However, when we looked at this same brain structure in the sleep-deprived participants, we could not find any significant learning activity whatsoever. It was as though sleep deprivation had shut down their memory in-box, and any new incoming information was simply being bounced
  • Simply disrupting the depth of an individual’s NREM sleep with infrequent sounds, preventing deep sleep and keeping the brain in shallow sleep, without waking the individual up will produce similar brain deficits and learning impairments
  • Memories formed without sleep are weaker memories, evaporating rapidly
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A night of sleep strengthens newly learned memories, boosting their retention

  • If you don’t sleep the very first night after learning, you lose the chance to consolidate those memories, even if you get lots of “catch-up” sleep thereafter

Alzheimer's disease

  • Sleep disturbance precedes the onset of Alzheimer’s disease by several years, suggesting that it may be an early-warning sign of the condition, or even a contributor to it
  • Over 60 percent of patients with Alzheimer’s disease have at least one clinical sleep disorder. Insomnia is especially common
  • Alzheimer’s disease is associated with the buildup of a toxic form of protein called beta-amyloid, which aggregates in sticky clumps, or plaques, within the brain. Amyloid plaques are poisonous to neurons, killing the surrounding brain cells
  • Amyloid plaques only affect some parts of the brain and not others. That area is the middle part of the frontal lobe—which is the same brain region essential for the electrical generation of deep NREM sleep in healthy young individuals. The more amyloid deposits there were in the middle regions of the frontal lobe, the more impaired the deep-sleep quality was in that older individual
  • Despite Alzheimer’s disease being typified by memory loss, the hippocampus—that key memory reservoir in the brain—is mysteriously unaffected by amyloid protein
  • Those individuals with the highest levels of amyloid deposits in the frontal regions of the brain had the most severe loss of deep sleep and, as a knock-on consequence, failed to successfully consolidate those new memories
  • Glymphatic system. Sewage network called the glymphatic system exists within the brain. Glial cells are distributed throughout your entire brain, situated side by side with the neurons that generate the electrical impulses of your brain. Just as the lymphatic system drains contaminants from your body, the glymphatic system collects and removes dangerous metabolic contaminants generated by the hard work performed by neurons in your brain, rather like a support team surrounding an elite athlete. Although the glymphatic system—the support team—is somewhat active during the day, Nedergaard and her team discovered that it is during sleep that this neural sanitization work kicks into high gear. Associated with the pulsing rhythm of deep NREM sleep comes a ten- to twentyfold increase in effluent expulsion from the brain. In what can be described as a nighttime power cleanse, the purifying work of the glymphatic system is accomplished by cerebrospinal fluid that bathes the brain.
  • The glial cells of the brain were shrinking in size by up to 60 percent during NREM sleep, enlarging the space around the neurons and allowing the cerebrospinal fluid to proficiently clean out the metabolic refuse left by the day’s neural activity. Think of the buildings of a large metropolitan city physically shrinking at night, allowing municipal cleaning crews easy access to pick up garbage strewn in the streets, followed by a good pressure-jet treatment of every nook and cranny. When we wake each morning, our brains can once again function efficiently thanks to this deep cleansing
  • One piece of toxic debris evacuated by the glymphatic system during sleep is amyloid protein—the poisonous element associated with Alzheimer’s disease. Other dangerous metabolic waste elements that have links to Alzheimer’s disease are also removed by the cleaning process during sleep, including a protein called tau, as well as stress molecules produced by neurons when they combust energy and oxygen during the day
  • Inadequate sleep and the pathology of Alzheimer’s disease interact in a vicious cycle. Without sufficient sleep, amyloid plaques build up in the brain, especially in deep-sleep generating regions, attacking and degrading them. The loss of deep NREM sleep caused by this assault therefore lessens the ability to remove amyloid from the brain at night, resulting in greater amyloid deposition. More amyloid, less deep sleep, less deep sleep, more amyloid, and so on and so forth
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Getting too little sleep across the adult life span will significantly raise your risk of developing Alzheimer’s disease

  • I have always found it curious that Margaret Thatcher and Ronald Reagan—two heads of state that were very vocal, if not proud, about sleeping only four to five hours a night—both went on to develop the ruthless disease

Chapter 8: Cancer, Heart Attacks, and a Shorter Life

Sleep Deprivation and the Body

I was once fond of saying, “Sleep is the third pillar of good health, alongside diet and exercise.” I have changed my tune. Sleep is more than a pillar; it is the foundation on which the other two health bastions sit

Sleep loss and the cardiovascular system

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Unhealthy sleep, unhealthy heart.

  • Progressively shorter sleep was associated with a 45 percent increased risk of developing and/or dying from coronary heart disease within seven to twenty-five years from the start of the study
  • Over a fourteen-year period, those sleeping six hours or less were 400 to 500 percent more likely to suffer one or more cardiac arrests than those sleeping more than six hours
  • Adults forty-five years or older who sleep fewer than six hours a night are 200 percent more likely to have a heart attack or stroke during their lifetime, as compared with those sleeping seven to eight hours a night
  • Part of the reason the heart suffers so dramatically under the weight of sleep deprivation concerns blood pressure
  • One night of modest sleep reduction—even just one or two hours—will promptly speed the contracting rate of a person’s heart, hour upon hour, and significantly increase the systolic blood pressure within their vasculature
  • Beyond accelerating your heart rate and increasing your blood pressure, a lack of sleep further erodes the fabric of those strained blood vessels, especially those that feed the heart itself, called the coronary arteries
  • Atherosclerosis. If you were one of the individuals who were obtaining just five to six hours each night or less, you were 200 to 300 percent more likely to suffer calcification of your coronary arteries over the next five years, relative to those individuals sleeping seven to eight hours

Sympathetic nervous system

  • The sympathetic nervous system is resolutely activating, inciting, even agitating. If needed, it will mobilize the evolutionarily ancient fight-or-flight stress response within the body, comprehensively and in a matter of seconds. Like an accomplished general in command of a vast military, the sympathetic nervous system can muster activity in a vast assortment of the body’s physiological divisions—from respiration, immune function, and stress chemicals to blood pressure and heart rate.
  • An acute stress response from the sympathetic nervous system, which is normally only deployed for short periods of time lasting minutes to hours, can be highly adaptive under conditions of credible threat, such as the potential of real physical attack. Survival is the goal, and these responses promote immediate action to accomplish just that. But leave that system stuck in the “on” position for long durations of time, and sympathetic activation becomes deeply maladaptive
  • For as long as the state of insufficient sleep lasts, and for some time thereafter, the body remains stuck in some degree of a fight-or-flight state
  • Through this central pathway of an overactive sympathetic nervous system, sleep deprivation triggers a domino effect that will spread like a wave of health damage throughout your body. It starts with removing a default resting brake that normally prevents your heart from accelerating in its rate of contraction. Once this brake is released, you will experience sustained speeds of cardiac beating.
  • As your sleep-deprived heart beats faster, the volumetric rate of blood pumped through your vasculature increases, and with that comes the hypertensive state of your blood pressure. Occurring at the same time is a chronic increase in a stress hormone called cortisol, which is triggered by the overactive sympathetic nervous system. One undesirable consequence of the sustained deluge of cortisol is the constriction of those blood vessels, triggering an even greater increase in blood pressure.
  • Making matters worse, growth hormone—a great healer of the body—which normally surges at night, is shut off by the state of sleep deprivation. Without growth hormone to replenish the lining of your blood vessels, called the endothelium, they will be slowly shorn and stripped of their integrity
  • During deep NREM sleep specifically, the brain communicates a calming signal to the fight-or-flight sympathetic branch of the body’s nervous system, and does so for long durations of the night. As a result, deep sleep prevents an escalation of this physiological stress that is synonymous with increased blood pressure, heart attack, heart failure, and stroke. This includes a calming effect on the contracting speed of your heart
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Daylight savings time. In the Northern Hemisphere, the switch to daylight savings time in March results in most people losing an hour of sleep opportunity. Should you tabulate millions of daily hospital records, as researchers have done, you discover that this seemingly trivial sleep reduction comes with a frightening spike in heart attacks the following day. Impressively, it works both ways. In the autumn within the Northern Hemisphere, when the clocks move forward and we gain an hour of sleep opportunity time, rates of heart attacks plummet the day after. A similar rise-and-fall relationship can be seen with the number of traffic accidents, proving that the brain, by way of attention lapses and microsleeps, is just as sensitive as the heart to very small perturbations of sleep. Most people think nothing of losing an hour of sleep for a single night, believing it to be trivial and inconsequential. It is anything but.

Sleep loss and metabolism

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The less you sleep, the more you are likely to eat

  • Sleeping less than seven or eight hours a night will increase your probability of gaining weight, being overweight, or being obese, and significantly increases your likelihood of developing type 2 diabetes

Diabetes

  • Excessively high levels of blood sugar, or glucose, over weeks or years inflicts a surprising harm to the tissues and organs of your body, worsens your health, and shortens your life span
  • In a healthy individual, the hormone insulin will trigger the cells of your body to swiftly absorb glucose from the bloodstream should it increase, as happens after eating a meal
  • If the cells of your body stop responding to insulin, however, they cannot efficiently absorb glucose from the blood
  • The research groups found far higher rates of type 2 diabetes among individuals that reported sleeping less than six hours a night routinely
  • Participants were limited to sleeping four hours a night for just six nights. By the end of that week, these (formerly healthy) participants were 40 percent less effective at absorbing a standard dose of glucose, compared to when they were fully rested
  • After participants had been restricted to four to five hours of sleep for a week, the cells of these tired individuals had become far less receptive to insulin. The cells were repelling rather than absorbing the dangerously high levels of glucose

Weight gain and obesity

  • When your sleep becomes short, you will gain weight
  • Two hormones controlling appetite: leptin and ghrelin. Leptin signals a sense of feeling full. When circulating levels of leptin are high, your appetite is blunted and you don’t feel like eating. Ghrelin, in contrast, triggers a strong sensation of hunger. When ghrelin levels increase, so, too, does your desire to eat. An imbalance of either one of these hormones can trigger increased eating and thus body weight
Hotel & food experiment

Over the past thirty years, my colleague Dr. Eve Van Cauter at the University of Chicago has tirelessly conducted research on the link between sleep and appetite that is as brilliant as it is impactful. Rather than depriving individuals of a full night of sleep, Van Cauter has taken a more relevant approach. She recognized that more than a third of individuals in industrialized societies sleep less than five to six hours a night during the week. So in a first series of studies of healthy young adults of perfectly normal weight, she began to investigate whether one week of this societally typical short sleep was enough to disrupt levels of either leptin or ghrelin or both. If you are a participant in one of Van Cauter’s studies, it feels rather more like a one-week stay at a hotel. You will get your own room, bed, clean sheets, a television, Internet access, etc.— everything except free tea and coffee, since no caffeine is allowed. In one arm of the experiment, you will be given an eight-and-a-half-hour sleep opportunity each night for five nights, recorded with electrodes placed on your head. In the other arm of the study, you are only allowed four to five hours of sleep for five nights, also measured with electrode recordings. In both study arms, you will receive exactly the same amount and type of food, and your degree of physical activity is also held constant. Each day, your sense of hunger and food intake are monitored, as are your circulating levels of leptin and ghrelin. Using precisely this experimental design in a group of healthy, lean participants, Van Cauter discovered that individuals were far more ravenous when sleeping four to five hours a night. This despite being given the same amount of food and being similarly active, which kept the hunger levels of these same individuals under calm control when they were getting eight or more hours of sleep. The strong rise of hunger pangs and increased reported appetite occurred rapidly, by just the second day of short sleeping.

From a metabolic perspective, the sleep-restricted participants had lost their hunger control. By limiting these individuals to what some in our society would think of as a “sufficient” amount of sleep (five hours a night), Van Cauter had caused a profound imbalance in the scales of hormonal food desire. By muting the chemical message that says “stop eating” (leptin), yet increasing the hormonal voice that shouts “please, keep eating” (ghrelin), your appetite remains unsatisfied when your sleep is anything less than plentiful, even after a kingly meal. As Van Cauter has elegantly described to me, a sleep-deprived body will cry famine in the midst of plenty.

  • Individuals were far more ravenous when sleeping four to five hours a night. This despite being given the same amount of food and being similarly active, which kept the hunger levels of these same individuals under calm control when they were getting eight or more hours of sleep. The strong rise of hunger pangs and increased reported appetite occurred by just the second day of short sleeping.
  • A sleep-deprived body will cry famine in the midst of plenty. By muting the chemical message that says “stop eating” (leptin), yet increasing the hormonal voice that shouts “please, keep eating” (ghrelin), your appetite remains unsatisfied when your sleep is anything less than plentiful, even after a kingly meal
Another hotel & food experiment

With another landmark study, Van Cauter proved this to be the case. Participants in this experiment again underwent two different conditions, acting as their own baseline control: four nights of eight and a half hours’ time in bed, and four nights of four and a half hours’ time in bed. Each day, participants were limited to the same level of physical activity under both conditions. Each day, they were given free access to food, and the researchers meticulously counted the difference in calorie consumption between the two experimental manipulations. When short sleeping, the very same individuals ate 300 calories more each day—or well over 1,000 calories before the end of the experiment—compared to when they were routinely getting a full night of sleep. Similar changes occur if you give people five to six hours of sleep over a ten-day period. Scale that up to a working year, and assuming one month of vacation in which sleep miraculously becomes abundant, and you will still have consumed more than 70,000 extra calories. Based on caloric estimates, that would cause 10 to 15 pounds of weight gain a year, each and every year (which may sound painfully familiar to many of us).

  • When short sleeping, the very same individuals ate 300 calories more each day
Last hotel & food experiment

Van Cauter’s next experiment was the most surprising (and devilish) of all. Fit, healthy individuals went through the same two different conditions as before: four nights of eight and a half hours’ time in bed, and four nights of four and a half hours’ time in bed. However, on the last day if each of the experimental conditions, something different happened. Participants were offered an additional food buffet stretched across a four-hour period. Set out in front of them was an assortment of foods, from meats, vegetables, bread, potatoes, and salad to fruit and ice cream. Set to one side, however, was access to a bonus snack bar filled with cookies, chocolate bars, chips, and pretzels. Participants could eat as much as they wanted in the four-hour period, with the buffet even being replenished halfway through. Importantly, the subjects ate alone, limiting social or stigmatizing influences that could alter their natural eating urges. Following the buffet, Van Cauter and her team once again quantified what participants ate, and how much they ate. Despite eating almost 2,000 calories during the buffet lunch, sleepdeprived participants dove into the snack bar. They consumed an additional 330 calories of snack foods after the full meal, compared to when they were getting plenty of sleep each night

  • Despite eating almost 2,000 calories during the buffet lunch, sleepdeprived participants dove into the snack bar. They consumed an additional 330 calories of snack foods after the full meal, compared to when they were getting plenty of sleep each night
  • Sleep loss increases levels of circulating endocannabinoids, which are chemicals produced by the body that are very similar to the drug cannabis. Like marijuana use, these chemicals stimulate appetite and increase your desire to snack, otherwise known as having the munchies
  • Some argue that we eat more when we are sleep-deprived because we burn extra calories when we stay awake. Sadly, this is not true
  • By sleep-depriving an individual for twenty-four hours straight and they will only burn an extra 147 calories, relative to a twenty-four-hour period containing a full eight hours of sleep
  • The extra calories that you eat when sleep-deprived far outweigh any nominal extra energy you burn while remaining awake
  • The less an individual sleeps, the less energy he or she feels they have, and the more sedentary and less willing to exercise they are in real-world settings
  • Van Cauter noticed that cravings for sweets (e.g., cookies, chocolate, and ice cream), heavy-hitting carbohydrate-rich foods (e.g., bread and pasta), and salty snacks (e.g., potato chips and pretzels) all increased by 30 to 40 percent when sleep was reduced by several hours each night. Less affected were protein-rich foods (e.g., meat and fish), dairy items (such as yogurt and cheese), and fatty foods, showing a 10 to 15 percent increase in preference by the sleepy participants.
  • Supervisory regions in the prefrontal cortex required for thoughtful judgments and controlled decisions had been silenced in their activity by a lack of sleep
  • High-calorie foods became significantly more desirable in the eyes of the participants when sleep-deprived. When we tallied up the extra food items that participants wanted when they were sleep-deprived, it amounted to an extra 600 calories.
  • A full night of sleep repairs the communication pathway between deep-brain areas that unleash hedonic desires and higher-order brain regions whose job it is to rein in these cravings.
  • Epidemiological studies have established that people who sleep less are the same individuals who are more likely to be overweight or obese
Figure of sleep loss - obesity correlation
image
  • Three-year-olds sleeping just ten and a half hours or less have a 45 percent increased risk of being obese by age seven than those who get twelve hours of sleep a night
  • When you are not getting enough sleep, the body becomes especially stingy about giving up fat. Instead, muscle mass is depleted while fat is retained
    • When given just five and a half hours of sleep opportunity, more than 70 percent of the pounds lost came from lean body mass—muscle, not fat. Switch to the group offered eight and a half hours’ time in bed each night and a far more desirable outcome was observed, with well over 50 percent of weight loss coming from fat while preserving muscle
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Short sleep (of the type that many adults in first-world countries commonly and routinely report) will increase hunger and appetite, compromise impulse control within the brain, increase food consumption (especially of highcalorie foods), decrease feelings of food satisfaction after eating, and prevent effective weight loss when dieting.

Sleep loss and reproductive system

  • Take a group of lean, healthy young males in their mid-twenties and limit them to five hours of sleep for one week. Sample the hormone levels circulating in the blood of these tired participants and you will find a marked drop in testosterone relative to their own baseline levels of testosterone when fully rested. The size of the hormonal blunting effect is so large that it effectively “ages” a man by ten to fifteen years in terms of testosterone virility
  • Men who report sleeping too little—or having poor-quality sleep—have a 29 percent lower sperm count than those obtaining a full and restful night of sleep, and the sperm themselves have more deformities
  • Males with low testosterone often feel tired and fatigued throughout the day. They find it difficult to concentrate on work tasks, as testosterone has a sharpening effect on the brain’s ability to focus
  • Routinely sleeping less than six hours a night results in a 20 percent drop in follicular-releasing hormone in women—a critical female reproductive element that peaks just prior to ovulation and is necessary for conception
  • In a report that brought together findings from studies over the past forty years of more than 100,000 employed women, those working irregular nighttime hours resulting in poor-quality sleep, such as nurses who performed shift work (a profession occupied almost exclusively by women at the time of these earlier studies), had a 33 percent higher rate of abnormal menstrual cycles than those working regular daytime hours. Moreover, the women working erratic hours were 80 percent more likely to suffer from issues of sub-fertility that reduced the ability to get pregnant.
  • Women who do become pregnant and routinely sleep less than eight hours a night are also significantly more likely to suffer a miscarriage in the first trimester, relative to those consistently sleeping eight hours or more a night.
Sundelin experiment

Sundelin took a group of healthy men and women ranging from eighteen to thirty-one years old. They were all photographed twice under identical indoor lighting conditions, same time of day (2:30 p.m.), hair down, no makeup for the women, clean-shaven for the men. What differed, however, was the amount of sleep these individuals were allowed to get before each of the photo shoots. In one of the sessions, the participants were given just five hours of sleep before being put in front of the camera, while in the other session, these same individuals got a full eight hours of sleep. The order of these two conditions was randomized as either first or second across the unwitting models. She brought another group of participants into the laboratory to act as independent judges. These individuals were naïve to the true purpose of the experiment, knowing nothing about the two different sleep manipulations that had been imposed on the people featured in the photographs. The judges viewed both sets of the pictures in a jumbled order and were asked to give ratings on three features: perceived health, tiredness, and attractiveness. Despite knowing nothing about the underlying premise of the study, thus operating blind to the different sleep conditions, the judges’ scores were unambiguous. The faces pictured after one night of short sleep were rated as looking more fatigued, less healthy, and significantly less attractive, compared with the appealing image of that same individual after they had slept a full eight hours. Sundelin had revealed the true face of sleep loss, and with it, ratified the long-held concept of “beauty sleep.”

  • The faces pictured after one night of short sleep were rated as looking more fatigued, less healthy, and significantly less attractive, compared with the appealing image of that same individual after they had slept a full eight hours
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Reproductive hormones, reproductive organs, and the very nature of physical attractiveness that has a say in reproductive opportunities: all are degraded by short sleeping

Sleep loss and the immune system

  • When you do fall ill, the immune system actively stimulates the sleep system, demanding more bed rest to help reinforce the war effort. Reduce sleep even for a single night, and that invisible suit of immune resilience is rudely stripped from your body
  • The less sleep an individual was getting in the week before facing the active common cold virus, the more likely it was that they would be infected and catch a cold
  • In those sleeping five hours on average, the infection rate was almost 50 percent. In those sleeping seven hours or more a night in the week prior, the infection rate was just 18 percent.
  • Those participants who obtained seven to nine hours’ sleep in the week before getting the flu shot generated a powerful antibody reaction, reflecting a robust, healthy immune system. In contrast, those in the sleep-restricted group mustered a paltry response, producing less than 50 percent of the immune reaction their well-slept counterparts were able to mobilize
  • Once you miss out on the benefit of sleep in the moment—here, regarding an immune response to this season’s flu—you cannot regain the benefit simply by trying to catch up on lost sleep. The damage is done, and some of that harm can still be measured a year later.
  • Natural killer cells are an elite and powerful squadron within the ranks of your immune system. Think of natural killer cells like the secret service agents of your body, whose job it is to identify dangerous foreign elements and eliminate them—007 types, if you will. One such foreign entity that natural killer cells will target are malignant (cancerous) tumor cells. Natural killer cells will effectively punch a hole in the outer surface of these cancerous cells and inject a protein that can destroy the malignancy. What you want, therefore, is a virile set of these James Bond–like immune cells at all times. That is precisely what you don’t have when sleeping too little.
  • A single night of four hours of sleep—such as going to bed at three a.m. and waking up at seven a.m.—swept away 70 percent of the natural killer cells circulating in the immune system, relative to a full eight-hour night of sleep.
  • A number of prominent epidemiological studies have reported that nighttime shift work, and the disruption to circadian rhythms and sleep that it causes, up your odds of developing numerous different forms of cancer considerably. To date, these include associations with cancer of the breast, cancer of the prostate, cancer of the uterus wall or the endometrium, and cancer of the colon
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    Denmark recently became the first country to pay worker compensation to women who had developed breast cancer after years of night-shift work in government-sponsored jobs, such as nurses and air cabin crew

  • A large European study of almost 25,000 individuals demonstrated that sleeping six hours or less was associated with a 40 percent increased risk of developing cancer, relative to those sleeping seven hours a night or more
  • Part of the problem relates back to the agitating influence of the sympathetic nervous system as it is forced into overdrive by a lack of sleep. Ramping up the body’s level of sympathetic nervous activity will provoke an unnecessary and sustained inflammation response from the immune system
  • The sleep-deprived mice suffered a 200 percent increase in the speed and size of cancer growth, relative to the well-rested group. The tumors were far more aggressive in the sleep-deficient animals. Their cancer had metastasized, spreading to surrounding organs, tissue, and bone
  • Sleep deprivation will diminish one form of these macrophages, called M1 cells, that otherwise help combat cancer. Yet sleep deprivation conversely boosts levels of an alternative form of macrophages, called M2 cells, which promote cancer growth
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Poor sleep quality therefore increases the risk of cancer development and, if cancer is established, provides a virulent fertilizer for its rapid and more rampant growth. Not getting sufficient sleep when fighting a battle against cancer can be likened to pouring gasoline on an already aggressive fire

Sleep loss, genes, and DNA

  • Chronic sleep loss will erode the very essence of biological life itself: your genetic code and the structures that encapsulate it
  • Each cell in your body has an inner core, or nucleus. Within that nucleus resides most of your genetic material in the form of deoxyribonucleic acid (DNA) molecules. DNA molecules form beautiful helical strands, like tall spiral staircases in an opulent home. Segments of these spirals provide specific engineering blueprints that instruct your cells to perform particular functions. These distinct segments are called genes
  • Anything that causes a shimmy or wobble in gene stability can have consequences
  • Deprive a mouse of sleep for just a day, as researchers have done, and the activity of these genes will drop by well over 200 percent
Derk-Jan Dijk Experiment

Dr. Derk-Jan Dijk, who directs the Surrey Sleep Research Center in England, has shown that the effects of insufficient sleep on genetic activity are just as striking in humans as they are in mice. Dijk and his prolific team examined gene expression in a group of healthy young men and women after having restricted them to six hours of sleep a night for one week, all monitored under strict laboratory conditions. After one week of subtly reduced sleep, the activity of a hefty 711 genes was distorted, relative to the genetic activity profile of these very same individuals when they were obtaining eight and a half hours of sleep for a week. Interestingly, the effect went in both directions: about half of those 711 genes had been abnormally revved up in their expression by the loss of sleep, while the other half had been diminished in their expression, or shut down entirely. The genes that were increased included those linked to chronic inflammation, cellular stress, and various factors that cause cardiovascular disease. Among those turned down were genes that help maintain stable metabolism and optimal immune responses. Subsequent studies have found that short sleep duration will also disrupt the activity of genes regulating cholesterol. In particular, a lack of sleep will cause a drop in high-density lipoproteins (HDLs)—a directional profile that has consistently been linked to cardiovascular disease

Beyond a simple lack of sleep, Dijk’s research team has further shown that inappropriately timed sleep, such as that imposed by jet lag or shift work, can have equally large effects on the expression of human genes as inadequate sleep. By pushing forward an individual’s sleep-wake cycle by a few hours each day for three days, Dijk disrupted a massive one-third of the transcribing activity of the genes in a group of young, healthy adults. Once again, the genes that were impacted controlled elemental life processes, such as the timing of metabolic, thermoregulatory, and immune activity, as well as cardiac health

  • After one week of subtly reduced sleep, the activity of a hefty 711 genes was distorted, relative to the genetic activity profile of these very same individuals when they were obtaining eight and a half hours of sleep for a week
  • A lack of sleep will cause a drop in high-density lipoproteins (HDLs)—a directional profile that has consistently been linked to cardiovascular disease
  • Insufficient sleep does more than alter the activity and readout of your genes; it attacks the very physical structure of your genetic material itself. The spiral strands of DNA in your cells float around in the nucleus, but are tightly wound together into structures called chromosomes, rather like weaving individual threads together to make a sturdy shoelace. And just like a shoelace, the ends of your chromosomes need to be protected by a cap or binding tip. For chromosomes, that protective cap is called a telomere. If the telomeres at the end of your chromosomes become damaged, your DNA spirals become exposed and your now vulnerable genetic code cannot operate properly, like a fraying shoelace without a tip. The less sleep an individual obtains, or the worse the quality of sleep, the more damaged the capstone telomeres of that individual’s chromosomes
  • Two individuals of the same chronological age would not appear to be of the same biological age on the basis of their telomere health if one was routinely sleeping five hours a night while the other was sleeping seven hours a night. The latter would appear “younger,” while the former would artificially have aged far beyond their calendar years

Part 3: How and Why We Dream

Chapter 9: REM-Sleep Dreaming

  • REM sleep is not the only time during sleep when we dream. Indeed, if you use a liberal definition of dreaming as any mental activity reported upon awakening from sleep, such as “I was thinking about rain,” then you technically dream in all stages of sleep. If I wake you from the deepest stage of NREM sleep, there is a 0 to 20 percent chance you will report some type of bland thought like this
  • But dreams as most of us think of them—those hallucinogenic, motoric, emotional, and bizarre experiences with a rich narrative—come from REM sleep, and many sleep researchers limit their definition of true dreaming to that which occurs in REM sleep

Your brain on dreams

  • During dreamless, deep NREM sleep, overall metabolic activity shows a modest decrease relative to that measured from an individual while they are resting but awake. However, something very different happens as the individual transitions into REM sleep and begins to dream. Numerous parts of the brain “light up” on the MRI scan as REM sleep takes hold, indicating a sharp increase in underlying activity
  • There are four main clusters of the brain that spike in activity when someone starts dreaming in REM sleep:
    • the visuospatial regions at the back of the brain, which enable complex visual perception;
    • the motor cortex, which instigates movement;
    • the hippocampus and surrounding regions that we have spoken about before, which support your autobiographical memory;
    • the deep emotional centers of the brain—the amygdala and the cingulate cortex, a ribbon of tissue that sits above the amygdala and lines the inner surface of your brain—both of which help generate and process emotions
  • The emotional regions of the brain are up to 30 percent more active in REM sleep compared to when we are awake
  • REM-sleep involves a pronounced deactivation of other brain regions—specifically, circumscribed regions of the far left and right sides of the prefrontal cortex
  • The prefrontal cortex acts like the CEO of the brain. This region, especially the left and right sides, manages rational thought and logical decision-making, sending “top-down” instructions to your more primitive deep-brain centers, such as those instigating emotions. And it is this CEO region of your brain, which otherwise maintains your cognitive capacity for ordered, logical thought, that is temporarily ousted each time you enter into the dreaming state of REM sleep.
Japanese Experimentors (dream readers)

The scientists placed each participant into an MRI scanner numerous times over the course of several days. Every time the participant fell asleep, the researchers would wait for a short while as they recorded the brain activity, and then wake the person up and obtain a dream report. Then they would let the person fall back to sleep, and repeat the procedure. The researchers continued to do this until they had gathered hundreds of dream reports and corresponding snapshots of brain activity from their participants. An example of one of the dream reports was: “I saw a big bronze statue . . . on a small hill, and below the hill there were houses, streets, and trees.” Kamitani and his team then distilled all of the dream reports down into twenty core content categories that were most frequent in the dreams of these individuals, such as books, cars, furniture, computers, men, women, and food. To obtain some kind of ground truth of what participants’ brain activity looked like when they actually perceived these types of visual images while awake, the researchers selected real photographs that represented each category (relevant pictures of cars, men, women, furniture, etc.). Participants were then placed back inside the MRI scanner and shown these images while awake as the researchers measured their brain activity again. Then, using these patterns of waking brain activity as a truth template of sorts, Kamitani went pattern-matching in the sea of sleeping brain activity. The concept is somewhat like DNA matching at a crime scene: the forensics team obtains a sample of the victim’s DNA that they use as a template, then go in search of a specific match from among the myriad possible samples. The scientists were able to predict with significant accuracy the content of participants’ dreams at any one moment in time using just the MRI scans, operating completely blind to the dream reports of the participants. Using the template data from the MRI images, they could tell if you were dreaming of a man or a woman, a dog or a bed, flowers or a knife.

The meaning and content of dreams

  • In his seminal book The Interpretation of Dreams (1899), Freud situated the dream unquestionably within the brain (that is, the mind, as there is arguably no ontological difference between the two) of an individual
  • Yet Freud was 50 percent right and 100 percent wrong
The problem with Freud's theory

Simply put, Freud believed that dreams came from unconscious wishes that had not been fulfilled. According to his theory, repressed desires, which he termed the “latent content,” were so powerful and shocking that if they appeared in the dream undisguised, they would wake the dreamer up. To protect the dreamer and his sleep, Freud believed there was a censor, or a filter, within the mind. Repressed wishes would pass through the censor and emerge disguised on the other side. The camouflaged wishes and desires, which Freud described as the “manifest content,” would therefore be unrecognizable to the dreamer, carrying no risk of jolting the sleeping individual awake. Freud believed that he understood how the censor worked and that, as a result, he could decrypt the disguised dream (manifest content) and reverse-engineer it to reveal the true meaning (latent content, rather like email encryption wherein the message is cloaked with a code). Without the decryption key, the content of the email cannot be read. Freud felt that he had discovered the decryption key to everyone’s dreams, and for many of his affluent Viennese patients, he offered the paid service of removing this disguise and revealing to them the original message content of their dreams. The problem, however, was the lack of any clear predictions from Freud’s theory. Scientists could not design an experiment that would test any tenets of his theory in order to help support or falsify it. It was Freud’s genius, and his simultaneous downfall. Science could never prove him wrong, which is why Freud continues to cast a long shadow on dream research to this day. But by the very same token, we could never prove the theory right. A theory that cannot be discerned true or false in this way will always be abandoned by science, and that is precisely what happened to Freud and his psychoanalytic practices

As a concrete example, consider the scientific method of carbon dating, used to determine the age of an organic object like a fossil. To validate the method, scientists would have the same fossil analyzed by several different carbon-dating machines that operated on the same underlying principle. If the method was scientifically robust, these independent machines should all return the same value of the fossil’s age. If they do not, the method must be flawed, as the data is inaccurate and cannot be replicated. The method of carbon dating was shown by this process to be legitimate. Not so for the Freudian psychoanalytic method of dream interpretation. Researchers have had different Freudian psychoanalysts interpret the same dream of an individual. If the method was scientifically reliable, with clear structured rules and metrics that the therapists could apply, then their respective interpretations of this dream should be the same—or at least have some degree of similarity in the extracted meaning they return. Instead, the psychoanalysts all gave remarkably different interpretations of this same dream, without any statistically significant similarity between them. There was no consistency. You cannot place a “QC”—quality control—sticker on Freudian psychoanalysis.

Author's demonstration of generic-ness of meaning of dreams

I often do the following with my students as a (perhaps cruel) demonstration. I start by asking anyone in the lecture auditorium if they would be willing to share a dream that I will interpret pro bono, on the spot. A few hands will go up. I point to one of the respondents and ask them their name—let’s call this one Kyle. I ask Kyle to tell me his dream. He says: I was running through an underground parking lot trying to find my car. I don’t know why I was running, but I felt like I really needed to get to my car. I found the car, um, but it wasn’t actually the car I owned but I thought it was my car in the dream. I tried to start the car, but each time I turned the key, nothing happened. Then my cell phone went off loudly and I woke up. In response, I look intensely and knowingly at Kyle, having been nodding my head throughout his description. I pause, and then say, “I know exactly what your dream is about, Kyle.” Amazed, he (and the rest of the lecture hall) awaits, my answer as though time has ground to a halt. After another long pause, I confidently enunciate the following: “Your dream, Kyle, is about time, and more specifically, about not having enough time to do the things you really want to do in life.” A wave of recognition, almost relief, washes over Kyle’s face, and the rest of the class appear equally convinced. Then I come clean. “Kyle—I have a confession. No matter what dream anyone ever tells me, I always give them that very same generic response, and it always seems to fit.” Thankfully, Kyle is a good sport and takes this with no ill grace, laughing with the rest of the class. I apologize once again to him. The exercise, however, importantly reveals the dangers of generic interpretations that feel very personal and uniquely individual, yet scientifically hold no specificity whatsoever

  • Of a total of 299 dream reports that Stickgold collected from these individuals across the fourteen days, a clear rerun of prior waking life events—day residue—was found in just 1 to 2 percent. Dreams are not, therefore, a wholesale replay of our waking lives
  • Between 35 and 55 percent of emotional themes and concerns that participants were having while they were awake during the day powerfully and unambiguously resurfaced in the dreams they were having at night

Chapter 10: Dreaming as Overnight Therapy

  • REM sleep is necessary, but REM sleep alone is not sufficient
  • REM sleep has 2 functions:
    • The first function involves nursing our emotional and mental health
    • The second is problem-solving and creativity

Dreaming - the soothing balm

  • Concentrations of a key stress-related chemical called noradrenaline are completely shut off within your brain when you enter this dreaming sleep state. In fact, REM sleep is the only time during the twenty-four-hour period when your brain is completely devoid of this anxiety-triggering molecule. Noradrenaline, also known as norepinephrine, is the brain equivalent to a body chemical you already know and have felt the effects of: adrenaline (epinephrine).
  • Think back to your childhood and try to recall some of the strongest memories you have. What you will notice is that almost all of them will be memories of an emotional nature: perhaps a particularly frightening experience of being separated from your parents, or almost being hit by a car on the street. Also notice, however, that your recall of these detailed memories is no longer accompanied by the same degree of emotion that was present at the time of the experience. You have not forgotten the memory, but you have cast off the emotional charge, or at least a significant amount of it
  • Through its therapeutic work at night, REM sleep performed the elegant trick of divorcing the bitter emotional rind from the information-rich fruit
  • If REM sleep did not perform this operation, we’d all be left with a state of chronic anxiety in our autobiographical memory networks; every time we recalled something salient, not only would we recall the details of the memory, but we would relive the same stressful emotional charge all over again.
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Sleep, and specifically REM sleep, was clearly needed in order for us to heal emotional wounds

  • It was only those patients who were expressly dreaming about the painful experiences around the time of the events who went on to gain clinical resolution from their despair, mentally recovering a year later as clinically determined by having no identifiable depression. Those who were dreaming, but not dreaming of the painful experience itself, could not get past the event, still being dragged down by a strong undercurrent of depression that remained.
  • It was not enough to have REM sleep, or even generic dreaming, when it comes to resolving our emotional past. Her patients required REM sleep with dreaming, but dreaming of a very specific kind: that which expressly involved dreaming about the emotional themes and sentiments of the waking trauma

Solving PTSD

  • Patients with PTSD, who are so often war veterans, have a difficult time recovering from horrific trauma experiences. They are frequently plagued by daytime flashbacks of these intrusive memories and suffer reoccurring nightmares. When a veteran soldier suffers a flashback triggered by, say, a car backfiring, they can relive the whole visceral traumatic experience again
  • If the brain cannot divorce the emotion from memory across the first night following a trauma experience, the theory suggests that a repeat attempt of emotional memory stripping will occur on the second night, as the strength of the “emotional tag” associated with the memory remains too high. If the process fails a second time, the same attempt will continue to repeat the next night, and the next night, like a broken record. This was precisely what appeared to be happening with the recurring nightmares of the trauma experience in PTSD patients
  • If I could lower the levels of noradrenaline in the brains of PTSD patients during sleep, thereby reinstating the right chemical conditions for sleep to do its trauma therapy work, then I should be able to restore healthier quality REM sleep. With that restored REM-sleep quality should come an improvement in the clinical symptoms of PTSD, and further, a decrease in the frequency of painful repetitive nightmares
  • In his PTSD clinic, Raskind had been treating his war veteran patients with a generic drug called prazosin to manage their high blood pressure. While the drug was somewhat effective for lowering blood pressure in the body, Raskind found it had a far more powerful yet entirely unexpected benefit within the brain: it alleviated the reoccurring nightmares in his PTSD patients
  • It turns out that the drug prazosin, which Raskind was prescribing simply to lower blood pressure, also has the fortuitous side effect of suppressing noradrenaline in the brain

Dreaming to decode waking experiences

  • There are regions of your brain whose job it is to read and decode the value and meaning of emotional signals, especially faces. And it is that very same essential set of brain regions, or network, that REM sleep recalibrates at night
  • Having had a full night of sleep, which contained REM sleep, participants demonstrated a beautifully precise tuning curve of emotional face recognition, rather like a stretched out V shape. But when those same participants were deprived of sleep, including the essential influence of REM sleep, they could no longer distinguish one emotion from another with accuracy. The tuning V of the brain had been changed, rudely pulled all the way up from the base and flattened into a horizontal line, as if the brain was in a state of generalized hypersensitivity without the ability to map gradations of emotional signals from the outside world
  • With the absence of such emotional acuity, normally gifted by the re-tuning skills of REM sleep at night, the sleep-deprived participants slipped into a default of fear bias, believing even gentle or somewhat friendly looking faces were menacing. The outside world had become a more threatening and aversive place when the brain lacked REM sleep—untruthfully so. Reality and perceived reality were no longer the same in the “eyes” of the sleepless brain. By removing REM sleep, we had, quite literally, removed participants’ levelheaded ability to read the social world around them.
  • This REM-sleep recalibration service comes into its own just prior to the transition into adolescence

Chapter 11: Dream Creativity and Dream Control

Aside from being a stoic sentinel that guards your sanity and emotional well-being, REM sleep and the act of dreaming have another distinct benefit: intelligent information processing that inspires creativity and promotes problem solving

Dreaming: the creative incubator

  • Deep NREM sleep strengthens individual memories, as we now know. But it is REM sleep that offers the masterful and complementary benefit of fusing and blending those elemental ingredients together, in abstract and highly novel ways.
  • During the dreaming sleep state, your brain will cogitate vast swaths of acquired knowledge, and then extract overarching rules and commonalities—“the gist.”
  • The dream of Dmitri Mendeleev on February 17, 1869 led to the periodic table of elements: the sublime ordering of all known constituent building blocks of nature.
Mendeleev story

Mendeleev, a Russian chemist of renowned ingenuity, had an obsession. He felt there might be an organizational logic to the known elements in the universe, euphemistically described by some as the search for God’s abacus. As proof of his obsession, Mendeleev made his own set of playing cards, with each card representing one of the universal elements and its unique chemical and physical properties. He would sit in his office, at home, or on long train rides, and maniacally deal the shuffled deck down onto a table, one card at a time, trying to deduce the rule of all rules that would explain how this ecumenical jigsaw puzzle fit together. For years he pondered the riddle of nature. For years he failed. After allegedly having not slept for three days and three nights, he’d reached a crescendo of frustration with the challenge. While the extent of sleep deprivation seems unlikely, a clear truth was Mendeleev’s continued failure to crack the code. Succumbing to exhaustion, and with the elements still swirling in his mind and refusing organized logic, Mendeleev lay down to sleep. As he slept, he dreamed, and his dreaming brain accomplished what his waking brain was incapable of. The dream took hold of the swirling ingredients in his mind and, in a moment of creative brilliance, snapped them together in a divine grid, with each row (period) and each column (group) having a logical progression of atomic and orbiting electron characteristics, respectively. In Mendeleev’s own words: II I saw in a dream a table where all the elements fell into place as required. Awakening, I immediately wrote it down on a piece of paper. Only in one place did a correction later seem necessary.

  • It was his dreaming brain, not his waking brain, that was able to perceive an organized arrangement of all known chemical elements
  • Other cases when genius appeared during sleep
  • Otto Loewi

    Loewi dreamed of a clever experiment on two frogs’ hearts that would ultimately reveal how nerve cells communicate with each other using chemicals (neurotransmitters) released across tiny gaps that separate them (synapses), rather than direct electrical signaling that could only happen if they were physically touching each other. So profound was this dream-implanted discovery that it won Loewi a Nobel Prize.

    Paul McCartney

    We also know of precious artistic gifts that have arisen from dreams. Consider Paul McCartney’s origination of the songs “Yesterday” and “Let It Be.” Both came to McCartney in his sleep. In the case of “Yesterday,” McCartney recounts the following dream-inspired awakening while he was staying in a small attic room of his family’s house on Wimpole Street, London, during the filming of the delightful movie Help: I woke up with a lovely tune in my head. I thought, “That’s great, I wonder what that is?” There was an upright piano next to me, to the right of the bed by the window. I got out of bed, sat at the piano, found G, found F sharp minor 7th—and that leads you through then to B to E minor, and finally back to E. It all leads forward logically. I liked the melody a lot, but because I’d dreamed it, I couldn’t believe I’d written it. I thought, “No, I’ve never written anything like this before.” But I had, which was the most magic thing!

    Keith Richards

    Not to be outdone, however, Keith Richards of the Rolling Stones has arguably the best sleep-inspired story, which gave rise to the opening riff of their song “Satisfaction.” Richards would routinely keep a guitar and tape recorder at his bedside to record ideas that would come to him in the night. He describes the following experience on May 7, 1965, after having returned to his hotel room in Clearwater, Florida, following a performance that evening: I go to bed as usual with my guitar, and I wake up the next morning, and I see that the tape is run to the very end. And I think, “Well, I didn’t do anything. Maybe I hit a button when I was asleep.” So I put it back to the beginning and pushed play and there, in some sort of ghostly version, is [the opening lines to “Satisfaction”]. It was a whole verse of it. And after that, there’s 40 minutes of me snoring. But there’s the song in its embryo, and I actually dreamt the damned thing.

    Mary Shelley (Frankenstein)

    The creative muse of dreaming has also sparked countless literary ideas and epics. Take the author Mary Shelley, who passed through a most frightening dream scene one summer night in 1816 while staying in one of Lord Byron’s estates near Lake Geneva—a dream she almost took to be waking reality. That dreamscape gave Shelley the vision and narrative for the spectacular gothic novel Frankenstein

Rem-sleep fuzzy logic

  • The dramatic alterations in brain activity during NREM and REM sleep, and their tidal shifts in neurochemical concentrations, do not reverse instantaneously when you awaken. Instead, the neural and chemical properties of that particular sleep stage will linger, creating the inertia period that separates true wakefulness from sleep, and last some minutes
  • Problem-solving abilities rocketed up, with participants solving 15 to 35 percent more puzzles when emerging from REM sleep compared with awakenings from NREM sleep or during daytime waking performance
  • The solutions simply “popped out” following awakenings from REM sleep
  • When you wake the brain from NREM or measure performance during the day, the operating principles of the brain are closely and logically connected, just as pictured in figure 14
  • Figure
    image
  • However, wake the brain up from REM sleep and the operating algorithm was completely different. The REM-sleep brain was shortcutting the obvious links and favoring very distantly related concepts
  • As we enter REM sleep and dreaming takes hold, an inspired form of memory mixology begins to occur. No longer are we constrained to see the most typical and plainly obvious connections between memory units. On the contrary, the brain becomes actively biased toward seeking out the most distant, nonobvious links between sets of information

Memory melding

Experiment with distant relations

let’s say that I teach you a simple relationship between two objects, A and B, such that A should be chosen over object B (A>B). Then I teach you another relationship, which is that object B should be chosen over object C (B>C). Two separate, isolated premises. If I then show you A and C together, and ask you which you would choose, you would very likely pick A over C because your brain made an inferential leap. You took two preexisting memories (A>B and B>C) and, by flexibly interrelating them (A>B>C), came up with a completely novel answer to a previously unasked question (A>C). This is the power of relational memory processing, and it is one that receives an accelerated boost from REM sleep. In a study conducted with my Harvard colleague Dr. Jeffrey Ellenbogen, we taught participants lots of these individual premises that were nested in a large chain of interconnectedness. Then we gave them tests that assessed not just their knowledge of these individual pairs, but also assessed whether they knew how these items connected together in the associative chain. Only those who had slept and obtained late-morning REM sleep, rich in dreaming, showed evidence of linking the memory elements together (A>B>C>D>E>F, etc.), making them capable of the most distant associative leaps (e.g., B>E). The very same benefit was found after daytime naps of sixty to ninety minutes that also included REM sleep. It is sleep that builds connections between distantly related informational elements that are not obvious in the light of the waking day. Our participants went to bed with disparate pieces of the jigsaw and woke up with the puzzle complete. It is the difference between knowledge (retention of individual facts) and wisdom (knowing what they all mean when you fit them together). Or, said more simply, learning versus comprehension. REM sleep allows your brain to move beyond the former and truly grasp the latter

  • It is sleep that builds connections between distantly related informational elements that are not obvious in the light of the waking day. Our participants went to bed with disparate pieces of the jigsaw and woke up with the puzzle complete. It is the difference between knowledge (retention of individual facts) and wisdom (knowing what they all mean when you fit them together). Or, said more simply, learning versus comprehension. REM sleep allows your brain to move beyond the former and truly grasp the latter
  • It is one of the key operations differentiating your brain from your computer. Computers can store thousands of individual files with precision. But standard computers do not intelligently interlink those files in numerous and creative combinations. Instead, computer files sit like isolated islands. Our human memories are, on the other hand, richly interconnected in webs of associations that lead to flexible, predictive powers. We have REM sleep, and the act of dreaming, to thank for much of that inventive hard work.

Code cracking and problem solving

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REM sleep is capable of creating abstract overarching knowledge and super-ordinate concepts out of sets of information

  • A delightful example is observed in infants abstracting complex grammatical rules in a language they must learn. Even eighteen-month-old babies have been shown to deduce high-level grammatical structure from novel languages they hear, but only after they have slept following the initial exposure. One example is language learning, and the extraction of new grammatical rules. Children exemplify this. They will start using the laws of grammar (e.g., conjunctions, tenses, pronouns, etc.) long before they understand what these things are. It is during sleep that their brains implicitly extract these rules, based on waking experience, despite the child lacking explicit awareness of the rules.
German experiment

Perhaps the most striking proof of sleep-inspired insight, and one I most frequently describe when giving talks to start-up, tech, or innovative business companies to help them prioritize employee sleep, comes from a study conducted by Dr. Ullrich Wagner at the University of Lübeck, Germany. Trust me when I say you’d really rather not be a participant in these experiments. Not because you have to suffer extreme sleep deprivation for days, but because you have to work through hundreds of miserably laborious number-string problems, almost like having to do long division for an hour or more. Actually “laborious” is far too generous a description. It’s possible some people have lost the will to live while trying to sit and solve hundreds of these number problems! I know, I’ve taken the test myself. You will be told that you can work through these problems using specific rules that are provided at the start of the experiment. Sneakily, what the researchers do not tell you about is the existence of a hidden rule, or shortcut, common across all the problems. If you figure out this embedded cheat, you can solve many more problems in a far shorter time. I’ll return to this shortcut in just a minute. After having had participants perform hundreds of these problems, they were to return twelve hours later and once again work through hundreds more of these mindnumbing problems. However, at the end of this second test session, the researchers asked whether the subjects had cottoned on to the hidden rule. Some of the participants spent that twelve-hour time delay awake across the day, while for others, that time window included a full eight-hour night of sleep. After time spent awake across the day, despite the chance to consciously deliberate on the problem as much as they desired, a rather paltry 20 percent of participants were able to extract the embedded shortcut. Things were very different for those participants who had obtained a full night of sleep—one dressed with late-morning, REM-rich slumber. Almost 60 percent returned and had the “ah-ha!” moment of spotting the hidden cheat—which is a threefold difference in creative solution insight afforded by sleep!

  • After time spent awake across the day, despite the chance to consciously deliberate on the problem as much as they desired, a rather paltry 20 percent of participants were able to extract the embedded shortcut. Things were very different for those participants who had obtained a full night of sleep—one dressed with late-morning, REM-rich slumber. Almost 60 percent returned and had the “ah-ha!” moment of spotting the hidden cheat—which is a threefold difference in creative solution insight afforded by sleep!
  • Little wonder, then, that you have never been told to “stay awake on a problem.” Instead, you are instructed to “sleep on it.”

Dream content matters

Maze experiment

Enter my collaborator Robert Stickgold, who designed a clever experiment in which participants explored a computerized virtual reality maze. During an initial learning session, he would start participants off from different random locations within the virtual maze and ask them to navigate their way out through exploratory trial and error. To aid their learning, Stickgold placed unique objects, such as a Christmas tree, to act as orientation or anchor points at specific locations within the virtual maze. Almost a hundred research participants explored the maze during the first learning session. Thereafter, half of them took a ninety-minute nap, while the other half remained awake and watched a video, all monitored with electrodes placed on the head and face. Throughout the ninety-minute epoch, Stickgold would occasionally wake the napping individuals and ask them about the content of any dreams they were having, or for the group that remained awake, ask them to report any particular thoughts that were going through their minds at the time. Following the ninety-minute period, and after another hour or so to overcome sleep inertia in those who napped, everyone was dropped back into the virtual maze and tested once more to see if their performance was any better than during initial learning. It should come as no surprise by now that those participants who took a nap showed superior memory performance on the maze task. They could locate the navigation clues with ease, finding their way around and out of the maze faster than those who had not slept. The novel result, however, was the difference that dreaming made. Participants who slept and reported dreaming of elements of the maze, and themes around experiences clearly related to it, showed almost ten times more improvement in their task performance upon awakening than those who slept just as much, and also dreamed, but did not dream of maze-related experiences. As in his earlier studies, Stickgold found that the dreams of these super-navigators were not a precise replay of the initial learning experience while awake. For example, one participant’s dream report stated: “I was thinking about the maze and kinda having people as checkpoints, I guess, and then that led me to think about when I went on this trip a few years ago and we went to see these bat caves, and they’re kind of like, maze-like.” There were no bats in Stickgold’s virtual maze, nor were there any other people or checkpoints. Clearly, the dreaming brain was not simply recapitulating or re-creating exactly what happened to them in the maze. Rather, the dream algorithm was cherry-picking salient fragments of the prior learning experience, and then attempting to place those new experiences within the back catalog of preexisting knowledge.

  • It should come as no surprise by now that those participants who took a nap showed superior memory performance on the maze task. They could locate the navigation clues with ease, finding their way around and out of the maze faster than those who had not slept
  • Participants who slept and reported dreaming of elements of the maze, and themes around experiences clearly related to it, showed almost ten times more improvement in their task performance upon awakening than those who slept just as much, and also dreamed, but did not dream of maze-related experiences
  • Questions that brain is trying to ask during REM-sleep
    • “How can I understand and connect that which I have recently learned with that I already know, and in doing so, discover insightful new links and revelations?”
    • “What have I done in the past that might be useful in potentially solving this newly experienced problem in the future?”
Edison case

We will never truly know if Edison was the shortsleeper that some, including himself, claim. What we do know, however, is that Edison was a habitual daytime napper. He understood the creative brilliance of dreaming, and used it ruthlessly as a tool, describing it as “the genius gap.” Edison would allegedly position a chair with armrests at the side of his study desk, on top of which he would place a pad of paper and a pen. Then he would take a metal saucepan and turn it upside down, carefully positioning it on the floor directly below the right-side armrest of the chair. If that were not strange enough, he would pick up two or three steel ball bearings in his right hand. Finally, Edison would settle himself down into the chair, right hand supported by the armrest, grasping the ball bearings. Only then would Edison ease back and allow sleep to consume him whole. At the moment he began to dream, his muscle tone would relax and he would release the ball bearings, which would crash on the metal saucepan below, waking him up. He would then write down all of the creative ideas that were flooding his dreaming mind. Genius, wouldn’t you agree?

Controlling your dreams (lucidity)

  • Lucid dreaming occurs at the moment when an individual becomes aware that he or she is dreaming.
  • However, the term is more colloquially used to describe gaining volitional control of what an individual is dreaming, and the ability to manipulate that experience, such as deciding to fly, or perhaps even the functions of it, such as problem solving
  • During REM sleep, however, all voluntary muscles are paralyzed, preventing the dreamer from acting out ongoing mental experience. Yet, the muscles that control the eyes are spared from this paralysis, and give this stage of sleep its frenetic name. Lucid dreamers were able to take advantage of this ocular freedom, communicating with the researchers through eye movements
  • Non-lucid dreamers find it difficult to believe that such deliberate eye movements are possible while someone is asleep, but watch a lucid dreamer do it a number of times, and it is impossible to deny.
  • When participants signaled the beginning of the lucid dream state, the scientists began taking MRI pictures of brain activity. Soon after, the sleeping participants signaled their intent to dream about moving their left hand, then their right hand, alternating over and over again, just as they did when awake. Their hands were not physically moving—they could not, due to the REM-sleep paralysis. But they were moving in the dream
  • Scientists had gained objective, brain-based proof that lucid dreamers can control when and what they dream while they are dreaming
  • Other studies using similar eye movement communication designs have further shown that individuals can deliberately bring themselves to timed orgasm during lucid dreaming, an outcome that, especially in males, can be objectively verified using physiological measures by (brave) scientists

Part 4: From Sleeping Pills to Society Transformed

Chapter 12: Sleep Disorders and Death Caused by No Sleep

For those seeking advice on sleep disorders, I recommend visiting the National Sleep Foundation website, and there you will find resources on sleep centers near you.

Somnambulism (sleepwalking)

  • The term “somnambulism” refers to sleep (somnus) disorders that involve some form of movement (ambulation). It encompasses conditions such as sleepwalking, sleep talking, sleep eating, sleep texting, sleep sex, and, very rarely, sleep homicide
  • Most people believe these events happen during REM sleep as an individual is dreaming, and specifically acting out ongoing dreams. However, all these events arise from the deepest stage of non-dreaming (NREM) sleep, and not dream (REM) sleep.
  • If you rouse an individual from a sleepwalking event and ask what was going through their mind, rarely will they report a thing—no dream scenario, no mental experience.
  • An unexpected spike in nervous system activity during deep sleep is one trigger to sleepwalking. This electrical jolt compels the brain to rocket from the basement of deep NREM sleep all the way to the penthouse of wakefulness, but it gets stuck somewhere in between (the thirteenth floor, if you will). Trapped between the two worlds of deep sleep and wakefulness, the individual is confined to a state of mixed consciousness—neither awake nor asleep. In this confused condition, the brain performs basic but well-rehearsed actions, such as walking over to a closet and opening it, placing a glass of water to the lips, or uttering a few words or sentences
  • Watching the video, the patient is clearly “awake” and behaving. But look at the brainwave activity and you realize that the patient, or at least their brain, is sound asleep. There are the clear and unmistakable slow electrical waves of deep NREM sleep, with no sign of fast, frenetic waking brainwave activity
  • For the most part, there is nothing pathological about sleepwalking or sleep talking. They are common in the adult population, and even more common in children
  • Most episodes of the condition are harmless. Occasionally, however, adult somnambulism can result in a much more extreme set of behaviors
  • Story of Kenneth Parks in 1987
  • Most somnambulism episodes (e.g., sleep walking, talking) are considered benign and do not require intervention

Insomnia

  • Being sleep deprived is not insomnia
  • In the field of medicine, sleep deprivation is considered as (i) having the adequate ability to sleep; yet (ii) giving oneself an inadequate opportunity to sleep—that is, sleep-deprived individuals can sleep, if only they would take the appropriate time to do so. Insomnia is the opposite: (i) suffering from an inadequate ability to generate sleep, despite (ii) allowing oneself the adequate opportunity to get sleep.
  • People suffering from insomnia therefore cannot produce sufficient sleep quantity/quality, even though they give themselves enough time to do so (seven to nine hours).
  • There are several different sub-types of insomnia
    • The first is sleep onset insomnia, which is difficulty falling asleep
    • The second is sleep maintenance insomnia, or difficulty staying asleep
  • Sleep onset and sleep maintenance insomnia are not mutually exclusive: you can have one or the other, or both
  • Clinical boxes to be checked to be considered a patient with insomnia:
  • Dissatisfaction with sleep quantity or quality (e.g., difficulty falling asleep, staying sleep, early-morning awakening)
    Suffering significant distress or daytime impairment
    Has insomnia at least three nights each week for more than three months
    Does not have any coexisting mental disorders or medical conditions that could otherwise cause what appears to be insomnia
  • Conclusion of symptoms: difficulty falling asleep, waking up in the middle of the night, waking up too early in the morning, difficulty falling back to sleep after waking up, and feeling unrefreshed throughout the waking day. If any of the characteristics of insomnia feel familiar to you, and have been present for several months, I suggest you consider seeking out a sleep medicine doctor
  • The emphasis on duration of the sleep problem (more than three nights a week, for more than three months) is important.
  • All of us will experience difficulty sleeping every now and then, which may last just one night or several. That is normal. There is usually an obvious cause, such as work stress or a flare-up in a social or romantic relationship. Once these things subside, though, the sleep difficulty usually goes away. Such acute sleep problems are generally not recognized as chronic insomnia, since clinical insomnia requires an ongoing duration of sleep difficulty, week after week after week
  • Approximately one out of every nine people you pass on the street will meet the strict clinical criteria for insomnia
  • Insomnia is almost twice as common in women than in men
  • African Americans and Hispanic Americans suffering higher rates of insomnia than Caucasian Americans
  • Should you relax the stringent clinical criteria and just use epidemiological data as a guide, it is probable that two out of every three people reading this book will regularly have difficulty falling or staying asleep at least one night a week, every week
  • The “sleep aid” industry is worth an astonishing $30 billion a year in the US
  • Insomnia shows some degree of genetic heritability, with estimates of 28 to 45 percent transmission rates from parent to child
  • External factors that cause poor sleep, such as too much bright light at night, the wrong ambient room temperature, caffeine, tobacco, and alcohol consumption can masquerade as insomnia
  • The two most common triggers of chronic insomnia are psychological: (1) emotional concerns, or worry, and (2) emotional distress, or anxiety.
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    In this fast-paced, information-overloaded modern world, one of the few times that we stop our persistent informational consumption and inwardly reflect is when our heads hit the pillow. There is no worse time to consciously do this. Little wonder that sleep becomes nearly impossible to initiate or maintain when the spinning cogs of our emotional minds start churning, anxiously worrying about things we did today, things that we forgot to do, things that we must face in the coming days, and even those far in the future. That is no kind of invitation for beckoning the calm brainwaves of sleep into your brain, peacefully allowing you to drift off into a full night of restful slumber

  • The biological cause of insomnia is an overactive sympathetic nervous system, which is the body’s aggravating fight-or-flight mechanism. The physiological consequences are increased heart rate, blood flow, metabolic rate, the release of stress-negotiating chemicals such as cortisol, and increased brain activation, all of which are beneficial in the acute moment of true threat or danger.
  • Health problems triggered by overactive sympathetic nervous system:
    • The raised metabolic rate triggered by fight-or-flight nervous system activity, which is common in insomnia patients, results in a higher core body temperature
    • Higher levels of the alertness-promoting hormone cortisol, and sister neurochemicals adrenaline and noradrenaline. All three of these chemicals raise heart rate
    • Altered patterns of brain activity linked with the body’s sympathetic nervous system which prevent sleep from happening
    • Patients with insomnia have a lower quality of sleep, reflected in shallower, less powerful electrical brainwaves during deep NREM. They also have more fragmented REM sleep, peppered by brief awakenings that they are not always aware of, yet still cause a degraded quality of dream sleep
  • Simply put, the insomnia patients could not disengage from a pattern of altering, worrisome, ruminative brain activity. Think of a time when you closed the lid of a laptop to put it to sleep, but came back later to find that the screen was still on, the cooling fans were still running, and the computer was still active, despite the closed lid. Normally this is because programs and routines are still running, and the computer cannot make the transition into sleep mode.
  • Recursive loops of emotional programs, together with retrospective and prospective memory loops, keep playing in the mind, preventing the brain from shutting down and switching into sleep mode
  • Insomnia patients are unable to function well during the day, cognitively and/or emotionally. In this way, insomnia is really a 24/7 disorder: as much a disorder of the day as of the night.
  • There is also paradoxical insomnia. Patients suffering from paradoxical insomnia therefore have an illusion, or misperception, of poor sleep that is not actually poor. As a result, such patients are treated as hypochondriacal

Narcolepsy

  • Narcolepsy is considered to be a neurological disorder
  • The condition usually emerges between ages ten and twenty years
  • Three core symptoms that make up the disorder: (1) excessive daytime sleepiness, (2) sleep paralysis, and (3) cataplexy
  • The daytime sleepiness is the equivalent of staying awake for three to four days straight.
  • The second symptom of narcolepsy is sleep paralysis: the frightening loss of ability to talk or move when waking up from sleep. In essence, you become temporarily locked in your body
  • Most of these events occur in REM sleep
  • There can be rare occasions when the paralysis of the REM state lingers on despite the brain having terminated sleep. As a result, you begin to wake up, but you are unable to lift your eyelids, turn over, cry out, or move any of the muscles that control your limbs. Gradually, the paralysis of REM sleep does wear off, and you regain control of your body, including your eyelids, arms, legs, and mouth.
  • Don’t worry if you have had an episode of sleep paralysis at some point in your life. It is not unique to narcolepsy. Around one in four healthy individuals will experience sleep paralysis, which is to say that it is as common as hiccups
  • The third and most astonishing core symptom of narcolepsy is called cataplexy. The word comes from the Greek kata, meaning down, and plexis, meaning a stroke or seizure—that is, a falling-down seizure. However, a cataplectic attack is not a seizure at all, but rather a sudden loss of muscle control. This can range from slight weakness wherein the head droops, the face sags, the jaw drops, and speech becomes slurred to a buckling of knees or a sudden and immediate loss of all muscle tone, resulting in total collapse on the spot
  • Cataplectic attacks are not random, but are triggered by moderate or strong emotions, positive or negative. Tell a funny joke to a narcoleptic patient, and they may literally collapse in front of you. Walk into a room and surprise a patient, perhaps while they are chopping food with a sharp knife, and they will collapse perilously. Even standing in a nice warm shower can be enough of a pleasurable experience to cause a patient’s legs to buckle and have a potentially dangerous fall caused by the cataplectic muscle loss.
  • If you saw a patient collapse under the influence of cataplexy, you would be convinced that they had fallen completely unconscious or into a powerful sleep. This is untrue. Patients are awake and continue to perceive the outside world around them
  • Scientists have examined the brains of narcoleptic patients in painstaking detail after they have passed away. During these postmortem investigations, they discovered a loss of almost 90 percent of all the cells that produce orexin. Worse still, the welcome sites, or receptors, of orexin that cover the surface of the power station of the brain stem were significantly reduced in number in narcoleptic patients, relative to normal individuals
  • Because of this lack of orexin, made worse by the reduced number of receptor sites to receive what little orexin does drip down, the sleep-wake state of the narcoleptic brain is unstable, like a faulty flip-flop switch. Never definitively on or off, the brain of a narcoleptic patient wobbles precariously around a middle point, teeter-tottering between sleep and wakefulness
  • Antidepressants are often prescribed to help with the second and third symptoms of narcolepsy—sleep paralysis and cataplexy—as they suppress REM sleep, and it is REM-sleep paralysis that is integral to these two symptoms. Nevertheless, antidepressants simply lower the incidence of both; they do not eradicate them.

How does the brain stem know that it’s time to turn off the lights, so to speak, and power down wakefulness to begin sleep?

  • Something has to switch the activating influence of the brain stem off, and in doing so, allow sleep to be switched on. That switch—the sleep-wake switch—is located just below the thalamus in the center of the brain, in a region called the hypothalamus.
  • It is the same neighborhood that houses the twenty-four-hour master biological clock
  • The sleep-wake switch within the hypothalamus has a direct line of communication to the power station regions of the brain stem
  • To do this, the sleep-wake switch in the hypothalamus releases a neurotransmitter called orexin.
  • When orexin is released down onto your brain stem, the switch has been unambiguously flipped, powering up the wakefulness-generating centers of the brain stem. Once activated by the switch, the brain stem pushes open the sensory gate of the thalamus, allowing the perceptual world to flood into your brain, transitioning you to full, stable wakefulness
  • At night, the opposite happens. The sleep-wake switch stops releasing orexin onto the brain stem.

Fatal familial insomnia

  • Michael Corke became the man who could not sleep—and paid for it with his life
  • At age forty he began having trouble sleeping
  • After eight straight weeks of no sleep, Corke’s mental faculties were quickly fading. This cognitive decline was matched in speed by the rapid deterioration of his body.
  • As Corke approached the six-month mark of no sleep, he was bedridden and approaching death.
  • Michael Corke died of a rare, genetically inherited disorder called fatal familial insomnia (FFI).
  • There are no treatments for this disorder, and there are no cures. Every patient diagnosed with the disorder has died within ten months, some sooner
  • The culprit is an anomaly of a gene called PrNP, which stands for prion protein. In this genetically crooked form, the protein begins targeting and destroying certain parts of the brain, resulting in a rapidly accelerating form of brain degeneration as the protein spreads.
  • Due to this puncturing attack by the prion proteins, the sensory gate of the thalamus was effectively stuck in a permanent “open” position
  • Since FFI is genetically inherited, we have been able to retrospectively trace some of its legacy through generations. That genetic lineage runs all the way back into Europe, and specifically Italy, where a number of afflicted families live
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The lack of sleep will kill a human being

Sleep deprivation vs food deprivation

Is sleep necessary for life?

  • Rats will die after fifteen days without sleep, on average
  • Death ensued as quickly from total sleep deprivation as it did from total food deprivation
  • Rats lost their lives almost as quickly from selective REM-sleep deprivation as they did following total sleep deprivation. A total absence of NREM sleep still proved fatal, it just took longer to inflict the same mortal consequence—fortyfive days, on average
  • Despite eating far more than their sleep-rested counterparts, the sleep-deprived rats rapidly began losing body mass during the study
  • They could no longer regulate their core body temperature. The more sleep-deprived the rats were, the colder they became, regressing toward ambient room temperature
  • The rats were effectively metabolizing themselves from the inside out in response to hypothermia
  • The privation of sleep had left these rats literally threadbare. Sores had appeared across the rats’ skin, together with wounds on their paws and tails. Not only was the metabolic system of the rats starting to implode, but so, too, was their immune system.They could not fend off even the most basic of infections at their epidermis or below it
  • The internal damage revealed by the final postmortem was equally ghastly: Complications ranged from fluid in the lungs and internal hemorrhaging to ulcers puncturing the stomach lining. Some organs, such as the liver, spleen, and kidneys, had physically decreased in size and weight. Others, like the adrenal glands that respond to infection and stress, were markedly enlarged. Circulating levels of the anxiety-related hormone corticosterone, released by the adrenal glands, had spiked in the sleepless rats
  • The fatal final straw turned out to be septicemia—a toxic and systemic (whole organism) bacterial infection that coursed through the rats’ bloodstream and ravaged the entire body until death. It was simple bacteria from the rats’ very own gut that inflicted the mortal blow—one that an otherwise healthy immune system would have easily quelled when fortified by sleep

How much sleep do you really need? The tribespeople study

  • The tribespeople were actually giving themselves a 7- to 8.5-hour sleep opportunity each night
  • The wristwatch device, which is neither a precise nor gold standard measure of sleep, estimated a range of 6 to 7.5 hours of this time was spent asleep. The sleep opportunity that these tribespeople provide themselves is therefore almost identical to what the National Sleep Foundation and the Centers for Disease Control and Prevention recommend for all adult humans: 7 to 9 hours of time in bed
  • The problem is that some people confuse time slept with sleep opportunity time. We know that many individuals in the modern world only give themselves 5 to 6.5 hours of sleep opportunity, which normally means they will only obtain around 4.5 to 6 hours of actual sleep
  • Need is not defined by that which is obtained, but rather whether or not that amount of sleep is sufficient to accomplish all that sleep does
  • The Hadza will face days where they obtain 1,400 calories or less, and routinely eat 300 to 600 fewer daily calories than those of us in modern Western cultures.
  • A large proportion of their year is therefore spent in a state of lower-level starvation, one that can trigger well-characterized biological pathways that reduce sleep time, even though sleep need remains higher than that obtained if food were abundant.
  • Concluding that humans, modern-living or pre-industrial, need less than seven hours of sleep therefore appears to be a wishful conceit, and a tabloid myth

Is sleeping 9 hours a night too much?

  • Epidemiological evidence suggests that the relationship between sleep and mortality risk is not linear, such that the more and more sleep you get, the lower and lower your death risk (and vice versa). Rather, there is an upward hook in death risk once the average sleep amount passes nine hours, resulting in a tilted backward J shape.
  • Sickness, especially sickness that activates a powerful immune response, activates more sleep. Ergo, the sickest individuals should be sleeping longer to battle back against illness using the suite of health tools sleep has on offer. It is simply that some illnesses, such as cancer, can be too powerful even for the mighty force of sleep to overcome, no matter how much sleep is obtained
  • The illusion created is that too much sleep leads to an early death, rather than the more tenable conclusion that the sickness was just too much despite all efforts to the contrary from the beneficial sleep extension
  • Sleep, like food, water, and oxygen, may share this relationship with mortality risk when taken to extremes. After all, wakefulness in the correct amount is evolutionarily adaptive, as is sleep.
  • There is an adaptive balance to be struck between wakefulness and sleep. In humans, that appears to be around sixteen hours of total wakefulness, and around eight hours of total sleep, for an average adult.

Chapter 13: What’s Stopping You from Sleeping?

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Modern society has taken one of nature’s perfect solutions (sleep) and neatly divided it into two problems: (1) a lack thereof at night, resulting in (2) an inability to remain fully awake during the day

Beyond longer commute times and “sleep procrastination” caused by late-evening television and digital entertainment—both of which are not unimportant in their top-and-tail snipping of our sleep time and that of our children—five key factors have powerfully changed how much and how well we sleep:

  • (1) constant electric light as well as LED light
  • (2) regularized temperature
  • (3) caffeine
  • (4) alcohol
  • (5) a legacy of punching time cards

Modern light

  • We are the only species that has managed to light the night to such dramatic effect
  • Humans are predominantly visual creatures. More than a third of our brain is devoted to processing visual information
  • For early Homo sapiens, most of our activities would have ceased after the sun set. They had to, as they were predicated on vision, supported by daylight
  • Before Edison, and before gas and oil lamps, the setting sun would take with it this full stream of daylight from our eyes, sensed by the twenty-four-hour clock within the brain. The loss of daylight informs our suprachiasmatic nucleus that nighttime is now in session; time to release the brake pedal on our pineal gland, allowing it to unleash vast quantities of melatonin that signal to our brains and bodies that darkness has arrived and it is time for bed
  • Artificial evening light, even that of modest strength, or lux, will fool your suprachiasmatic nucleus into believing the sun has not yet set. The brake on melatonin, which should otherwise have been released with the timing of dusk, remains forcefully applied within your brain under duress of electric light
  • Sleep in modern humans is delayed from taking off the evening runway, which would naturally occur somewhere between eight and ten p.m.
  • Artificial light in modern societies thus tricks us into believing night is still day, and does so using a physiological lie.
  • The degree to which evening electric light winds back your internal twenty-four-hour clock is important: usually two to three hours each evening, on average
  • By delaying the release of melatonin, artificial evening light makes it considerably less likely that you’ll be able to fall asleep at a reasonable time
  • What of a petite bedside lamp? — Even a hint of dim light—8 to 10 lux—has been shown to delay the release of nighttime melatonin in humans. The feeblest of bedside lamps pumps out twice as much: anywhere from 20 to 80 lux. A subtly lit living room, where most people reside in the hours before bed, will hum at around 200 lux. Despite being just 1 to 2 percent of the strength of daylight, this ambient level of incandescent home lighting can have 50 percent of the melatonin-suppressing influence within the brain.
  • Evening blue LED light has twice the harmful impact on nighttime melatonin suppression than the warm, yellow light from old incandescent bulbs, even when their lux intensities are matched
  • 90 percent of individuals regularly used some form of portable electronic device sixty minutes or less before bedtime. It has a very real impact on your melatonin release, and thus ability to time the onset of sleep
iPad vs Paper book experiment

One of the earliest studies found that using an iPad—an electronic tablet enriched with blue LED light—for two hours prior to bed blocked the otherwise rising levels of melatonin by a significant 23 percent. A more recent report took the story several concerning steps further. Healthy adults lived for a two-week period in a tightly controlled laboratory environment. The two-week period was split in half, containing two different experimental arms that everyone passed through: (1) five nights of reading a book on an iPad for several hours before bed (no other iPad uses, such as email or Internet, were allowed), and (2) five nights of reading a printed paper book for several hours before bed, with the two conditions randomized in terms of which the participants experienced as first or second. Compared to reading a printed book, reading on an iPad suppressed melatonin release by over 50 percent at night. Indeed, iPad reading delayed the rise of melatonin by up to three hours, relative to the natural rise in these same individuals when reading a printed book. When reading on the iPad, their melatonin peak, and thus instruction to sleep, did not occur until the early- morning hours, rather than before midnight. Unsurprisingly, individuals took longer to fall asleep after iPad reading relative to print-copy reading. But did reading on the iPad actually change sleep quantity/quality above and beyond the timing of melatonin? It did, in three concerning ways. First, individuals lost significant amounts of REM sleep following iPad reading. Second, the research subjects felt less rested and sleepier throughout the day following iPad use at night. Third was a lingering aftereffect, with participants suffering a ninety-minute lag in their evening rising melatonin levels for several days after iPad use ceased—almost like a digital hangover effect

  • One of the earliest studies found that using an iPad for two hours prior to bed blocked the otherwise rising levels of melatonin by a significant 23 percent
  • Compared to reading a printed book, reading on an iPad suppressed melatonin release by over 50 percent at night.
  • iPad reading delayed the rise of melatonin by up to three hours, relative to the natural rise in these same individuals when reading a printed book
  • Individuals lost significant amounts of REM sleep following iPad reading
  • The research subjects felt less rested and sleepier throughout the day following iPad use at night
  • A lingering aftereffect, with participants suffering a ninety-minute lag in their evening rising melatonin levels for several days after iPad use ceased—almost like a digital hangover effect.
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Using LED devices at night impacts our natural sleep rhythms, the quality of our sleep, and how alert we feel during the day

  • A good start is to create lowered, dim light in the rooms where you spend your evening hours.
  • Avoid powerful overhead lights. Mood lighting is the order of the night.
  • Some committed individuals will even wear yellow-tinted glasses indoors in the afternoon and evening to help filter out the most harmful blue light that suppresses melatonin.
  • Maintaining complete darkness throughout the night is equally critical, the easiest fix for which comes from blackout curtains.
  • Finally, you can install software on your computers, phones, and tablet devices that gradually de-saturate the harmful blue LED light as evening progresses

Alcohol

  • Short of prescription sleeping pills, the most misunderstood of all “sleep aids” is alcohol. Many individuals believe alcohol helps them to fall asleep more easily, or even offers sounder sleep throughout the night. Both are resolutely untrue
  • Alcohol is in a class of drugs called sedatives. It binds to receptors within the brain that prevent neurons from firing their electrical impulses
  • Alcohol immobilizes the prefrontal cortex part of our brain first. As a result, we “loosen up,” becoming less controlled and more extroverted. But anatomically targeted brain sedation it still is
  • Give alcohol a little more time, and it begins to sedate other parts of the brain, dragging them down into a stupefied state, just like the prefrontal cortex
  • Sedation is not sleep. Alcohol sedates you out of wakefulness, but it does not induce natural sleep.
  • The electrical brainwave state you enter via alcohol is not that of natural sleep; rather, it is akin to a light form of anesthesia
  • Alcohol fragments sleep, littering the night with brief awakenings. Alcohol-infused sleep is therefore not continuous and, as a result, not restorative
  • Unfortunately, most of these nighttime awakenings go unnoticed by the sleeper since they don’t remember them
  • Alcohol is one of the most powerful suppressors of REM sleep that we know of. When the body metabolizes alcohol it produces by-product chemicals called aldehydes and ketones. The aldehydes in particular will block the brain’s ability to generate REM sleep
7-day study experiment

To wit, researchers recruited a large group of college students for a seven-day study. The participants were assigned to one of three experimental conditions. On day 1, all the participants learned a novel, artificial grammar, rather like learning a new computer coding language or a new form of algebra. It was just the type of memory task that REM sleep is known to promote. Everyone learned the new material to a high degree of proficiency on that first day—around 90 percent accuracy. Then, a week later, the participants were tested to see how much of that information had been solidified by the six nights of intervening sleep. What distinguished the three groups was the type of sleep they had. In the first group—the control condition—participants were allowed to sleep naturally and fully for all intervening nights. In the second group, the experimenters got the students a little drunk just before bed on the first night after daytime learning. They loaded up the participants with two to three shots of vodka mixed with orange juice, standardizing the specific blood alcohol amount on the basis of gender and body weight. In the third group, they allowed the participants to sleep naturally on the first and even the second night after learning, and then got them similarly drunk before bed on night 3. Note that all three groups learned the material on day 1 while sober, and were tested while sober on day 7. This way, any difference in memory among the three groups could not be explained by the direct effects of alcohol on memory formation or later recall, but must be due to the disruption of the memory facilitation that occurred in between. On day 7, participants in the control condition remembered everything they had originally learned, even showing an enhancement of abstraction and retention of knowledge relative to initial levels of learning, just as we’d expect from good sleep. In contrast, those who had their sleep laced with alcohol on the first night after learning suffered what can conservatively be described as partial amnesia seven days later, forgetting more than 50 percent of all that original knowledge. This fits well with evidence we discussed earlier: that of the brain’s non-negotiable requirement for sleep the first night after learning for the purposes of memory processing. The real surprise came in the results of the third group of participants. Despite getting two full nights of natural sleep after initial learning, having their sleep doused with alcohol on the third night still resulted in almost the same degree of amnesia—40 percent of the knowledge they had worked so hard to establish on day 1 was forgotten. The overnight work of REM sleep, which normally assimilates complex memory knowledge, had been interfered with by the alcohol. More surprising, perhaps, was the realization that the brain is not done processing that knowledge after the first night of sleep. Memories remain perilously vulnerable to any disruption of sleep (including that from alcohol) even up to three nights after learning, despite two full nights of natural sleep prior.

  • On day 7, participants in the control condition remembered everything they had originally learned, even showing an enhancement of abstraction and retention of knowledge relative to initial levels of learning, just as we’d expect from good sleep. In contrast, those who had their sleep laced with alcohol on the first night after learning suffered what can conservatively be described as partial amnesia seven days later, forgetting more than 50 percent of all that original knowledge
  • Despite getting two full nights of natural sleep after initial learning, having their sleep doused with alcohol on the third night still resulted in almost the same degree of amnesia—40 percent of the knowledge they had worked so hard to establish on day 1 was forgotten
  • The brain is not done processing that knowledge after the first night of sleep. Memories remain perilously vulnerable to any disruption of sleep (including that from alcohol) even up to three nights after learning, despite two full nights of natural sleep prior
  • Go to the pub for a drink in the morning. That way, the alcohol will be out of your system before sleep.
  • Many people enjoy a glass of wine with dinner, even an aperitif thereafter. But it takes your liver and kidneys many hours to degrade and excrete that alcohol, even if you are an individual with fast-acting enzymes for ethanol decomposition.
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Nightly alcohol will disrupt your sleep, and the annoying advice of abstinence is the best, and most honest, I can offer

Temperature

  • Thermal environment, specifically the proximal temperature around your body and brain, is perhaps the most underappreciated factor determining the ease with which you will fall asleep tonight, and the quality of sleep you will obtain
  • To successfully initiate sleep your core temperature needs to decrease by 2 to 3 degrees Fahrenheit, or about 1 degree Celsius
  • You will always find it easier to fall asleep in a room that is too cold than too hot
  • Your nocturnal melatonin levels are controlled not only by the loss of daylight at dusk, but also the drop in temperature that coincides with the setting sun
  • Your body is not passive in letting the cool of night lull it into sleep, but actively participates
  • Most of the thermic work is performed by three parts of your body in particular: your hands, your feet, and your head
  • Warm hands and feet help your body’s core cool, inducing inviting sleep quickly and efficiently
  • Water, warm or cold, helps dissipate heat from the surface of the skin as it evaporates, thereby cooling the inner body core
  • The need to dump heat from our extremities is also the reason that you may occasionally stick your hands and feet out from underneath the bedcovers at night due to your core becoming too hot, usually without your knowing
  • Through climate-controlled homes with central heat and air-conditioning, and the use of bedcovers and pajamas, we have architected a minimally varying or even constant thermal tenor in our bedrooms
  • A bedroom temperature of around 65 degrees Fahrenheit (18.3°C) is ideal for the sleep of most people, assuming standard bedding and clothing
  • Lower than 55 degrees Fahrenheit (12.5°C) can be harmful rather than helpful to sleep, unless warm bedding or nightclothes are used.
  • Selectively warming the feet and hands by just a small amount (1°F, or about 0.5°C) caused a local swell of blood to these regions, thereby charming heat out of the body’s core, where it had been trapped. The result of all this ingenuity: sleep took hold of the participants in a significantly shorter time, allowing them to fall asleep 20 percent faster than was usual
  • Before the body-cooling therapy, these groups had a 58 percent probability of waking up in the last half of the night and struggled to get back to sleep—a classic hallmark of sleep maintenance insomnia. This number tumbled to just a 4 percent likelihood when receiving thermal help from the bodysuit
  • Hot baths prior to bed can also induce 10 to 15 percent more deep NREM sleep in healthy adults
    • You do not fall asleep faster because you are toasty and warm to the core. Instead, the hot bath invites blood to the surface of your skin, giving you that flushed appearance. When you get out of the bath, those dilated blood vessels on the surface quickly help radiate out inner heat, and your core body temperature plummets

Alarm clocks

  • Adding to the harm of evening light and constant temperature, the industrial era inflicted another damaging blow to our sleep: enforced awakening
  • Participants artificially wrenched from sleep will suffer a spike in blood pressure and a shock acceleration in heart rate caused by an explosive burst of activity from the fight-or-flight branch of the nervous system
  • Most of us are unaware of an even greater danger that lurks within the alarm clock: the snooze button
  • Using the snooze feature means that you will repeatedly inflict that cardiovascular assault again and again within a short span of time
  • Waking up at the same time of day, every day, no matter if it is the week or weekend is a good recommendation for maintaining a stable sleep schedule if you are having difficulty with sleep. Indeed, it is one of the most consistent and effective ways of helping people with insomnia get better sleep

Chapter 14: Pills vs. Therapy

  • In the past month, almost 10 million people in America will have swallowed some kind of a sleeping aid
  • Sleeping pills do not provide natural sleep, can damage health, and increase the risk of life-threatening diseases

Do sleeping pills help?

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No past or current sleeping medications on the legal (or illegal) market induce natural sleep

  • The older sleep medications—termed “sedative hypnotics,” such as diazepam—were blunt instruments. They sedated you rather than assisting you into sleep. Most of the newer sleeping pills on the market present a similar situation, though they are slightly less heavy in their sedating effects
  • Sleeping pills effectively knock out the higher regions of your brain’s cortex
  • The waking grogginess can lead people to reach for more cups of coffee or tea to rev themselves up with caffeine throughout the day and evening. That caffeine, in turn, makes it harder for the individual to fall asleep at night, worsening the insomnia. In response, people often take an extra half or whole sleeping pill at night to combat the caffeine, but this only amplifies the next-day grogginess from the drug hangover. Even greater caffeine consumption then occurs, perpetuating the downward spiral.
  • Another deeply unpleasant feature of sleeping pills is rebound insomnia. When individuals stop taking these medications, they frequently suffer far worse sleep, sometimes even worse than the poor sleep that led them to seek out sleeping pills to begin with
  • The majority of prescription sleeping pills are, after all, in a class of physically addictive drugs. Dependency scales with continued use, and withdrawal ensues in abstinence
  • Both the placebo and the sleeping pills reduced the time it took people to fall asleep (between ten and thirty minutes), but the change was not statistically different between the two. In other words, there was no objective benefit of these sleeping pills beyond that which a placebo offered

The harmful effects

Ambien experiment

After a period of intense learning, researchers at the University of Pennsylvania gave animals a weight-appropriate dose of Ambien or a placebo and then examined the change in brain rewiring after sleep in both groups. As expected, natural sleep solidified memory connections within the brain in the placebo condition that had been formed during the initial learning phase. Ambien-induced sleep, however, not only failed to match these benefits (despite the animals sleeping just as long), but caused a 50 percent weakening (unwiring) of the brain-cell connections originally formed during learning. In doing so, Ambienlaced sleep became a memory eraser, rather than engraver.

  • Ambien-induced sleep, however, not only failed to match these benefits (despite the animals sleeping just as long), but caused a 50 percent weakening (unwiring) of the brain-cell connections originally formed during learning
  • Although users of sleeping pills may fall asleep nominally faster at night, they should expect to wake up with few(er) memories of yesterday
  • Individuals using prescription sleep medications are significantly more likely to die and to develop cancer than those who do not
  • Those taking sleeping pills were 4.6 times more likely to die over this short two-and-a-half-year period than those who were not using sleeping pills. Kripke further discovered that the risk of death scaled with the frequency of use. Those individuals classified as heavy users, defined as taking more than 132 pills per year, were 5.3 times more likely to die over the study period than matched control participants who were not using sleeping pills
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  • Even very occasional users—those defined as taking just eighteen pills per year—were still 3.6 times more likely to die at some point across the assessment window than non-users
  • One frequent cause of mortality appears to be higher-than-normal rates of infection. Another cause of death linked to sleeping pill use is an increased risk for fatal car accidents. Higher risk for falls at night was a further mortality factor, particularly in the elderly. Additional adverse associations in users of prescription sleeping pills included higher rates of heart disease and stroke
  • Individuals taking sleeping pills were 30 to 40 percent more likely to develop cancer within the two-and-a-half-year period of the study than those who were not
  • No study to date has shown that sleeping pills save lives

CBT-I practice

  • Currently, the most effective of the sleep improvement methods is called cognitive behavioral therapy for insomnia, or CBT-I, and it is rapidly being embraced by the medical community as the first-line treatment
  • The obvious methods involve reducing caffeine and alcohol intake, removing screen technology from the bedroom, and having a cool bedroom
  • In addition, patients must
    • (1) establish a regular bedtime and wake-up time, even on weekends,
    • (2) go to bed only when sleepy and avoid sleeping on the couch early/mid-evenings,
    • (3) never lie awake in bed for a significant time period; rather, get out of bed and do something quiet and relaxing until the urge to sleep returns,
    • (4) avoid daytime napping if you are having difficulty sleeping at night,
    • (5) reduce anxiety-provoking thoughts and worries by learning to mentally decelerate before bed, and
    • (6) remove visible clockfaces from view in the bedroom, preventing clock-watching anxiety at night
  • One of the more paradoxical CBT-I methods used to help insomniacs sleep is to restrict their time spent in bed, perhaps even to just six hours of sleep or less to begin with. By keeping patients awake for longer, we build up a strong sleep pressure—a greater abundance of adenosine. Under this heavier weight of sleep pressure, patients fall asleep faster, and achieve a more stable, solid form of sleep across the night. In this way, a patient can regain their psychological confidence in being able to self-generate and sustain healthy, rapid, and sound sleep, night after night
  • CBT-I is more effective than sleeping pills in addressing numerous problematic aspects of sleep for insomnia sufferers. CBT-I consistently helps people fall asleep faster at night, sleep longer, and obtain superior sleep quality by significantly decreasing the amount of time spent awake at night

General good sleep practices

  • Going to bed and waking up at the same time of day no matter what. It is perhaps the single most effective way of helping improve your sleep, even though it involves the use of an alarm clock
  • In younger, healthy adults, exercise frequently increases total sleep time, especially deep NREM sleep. It also deepens the quality of sleep, resulting in more powerful electrical brainwave activity
  • Subjective sleep quality improves, as does total amount of sleep. Moreover, the time it takes participants to fall asleep is usually less, and they report waking up fewer times across the night
  • Subjects did not consistently sleep better at night on the days they exercised compared with the days when they were not required to exercise, as one would expect
  • When sleep was poor the night prior, exercise intensity and duration were far worse the following day. When sleep was sound, levels of physical exertion were powerfully maximal the next day. In other words, sleep may have more of an influence on exercise than exercise has on sleep
  • Participants also feel more alert and energetic as a result of the sleep improvement, and signs of depression proportionally decrease
  • Try not to exercise right before bed. Body temperature can remain high for an hour or two after physical exertion
  • Severe caloric restriction, such as reducing food intake to just 800 calories a day for one month, makes it harder to fall asleep normally, and decreases the amount of deep NREM sleep at night
  • Eating a highcarbohydrate, low-fat diet for two days decreases the amount of deep NREM sleep at night, but increases the amount of REM sleep dreaming, relative to a two-day diet low in carbohydrates and high in fat
  • A four-day diet high in sugar and other carbohydrates, but low in fiber, resulted in less deep NREM sleep and more awakenings at night
  • Avoid going to bed too full or too hungry, and shy away from diets that are excessively biased toward carbohydrates (greater than 70 percent of all energy intake), especially sugar.

⭐12 tips for healthy sleep

  1. Stick to a sleep schedule. Go to bed and wake up at the same time each day. As creatures of habit, people have a hard time adjusting to changes in sleep patterns. Sleeping later on weekends won’t fully make up for a lack of sleep during the week and will make it harder to wake up early on Monday morning. Set an alarm for bedtime. Often we set an alarm for when it’s time to wake up but fail to do so for when it’s time to go to sleep. If there is only one piece of advice you remember and take from these twelve tips, this should be it.
  2. Exercise is great, but not too late in the day. Try to exercise at least thirty minutes on most days but not later than two to three hours before your bedtime.
  3. Avoid caffeine and nicotine. Coffee, colas, certain teas, and chocolate contain the stimulant caffeine, and its effects can take as long as eight hours to wear off fully. Therefore, a cup of coffee in the late afternoon can make it hard for you to fall asleep at night. Nicotine is also a stimulant, often causing smokers to sleep only very lightly. In addition, smokers often wake up too early in the morning because of nicotine withdrawal.
  4. Avoid alcoholic drinks before bed. Having a nightcap or alcoholic beverage before sleep may help you relax, but heavy use robs you of REM sleep, keeping you in the lighter stages of sleep. Heavy alcohol ingestion also may contribute to impairment in breathing at night. You also tend to wake up in the middle of the night when the effects of the alcohol have worn off.
  5. Avoid large meals and beverages late at night. A light snack is okay, but a large meal can cause indigestion, which interferes with sleep. Drinking too many fluids at night can cause frequent awakenings to urinate.
  6. If possible, avoid medicines that delay or disrupt your sleep. Some commonly prescribed heart, blood pressure, or asthma medications, as well as some over-the-counter and herbal remedies for coughs, colds, or allergies, can disrupt sleep patterns. If you have trouble sleeping, talk to your health care provider or pharmacist to see whether any drugs you’re taking might be contributing to your insomnia and ask whether they can be taken at other times during the day or early in the evening.
  7. Don’t take naps after 3 p.m. Naps can help make up for lost sleep, but late afternoon naps can make it harder to fall asleep at night.
  8. Relax before bed. Don’t overschedule your day so that no time is left for unwinding. A relaxing activity, such as reading or listening to music, should be part of your bedtime ritual.
  9. Take a hot bath before bed. The drop in body temperature after getting out of the bath may help you feel sleepy, and the bath can help you relax and slow down so you’re more ready to sleep.
  10. Dark bedroom, cool bedroom, gadget-free bedroom. Get rid of anything in your bedroom that might distract you from sleep, such as noises, bright lights, an uncomfortable bed, or warm temperatures. You sleep better if the temperature in the room is kept on the cool side. A TV, cell phone, or computer in the bedroom can be a distraction and deprive you of needed sleep. Having a comfortable mattress and pillow can help promote a good night’s sleep. Individuals who have insomnia often watch the clock. Turn the clock’s face out of view so you don’t worry about the time while trying to fall asleep.
  11. Have the right sunlight exposure. Daylight is key to regulating daily sleep patterns. Try to get outside in natural sunlight for at least thirty minutes each day. If possible, wake up with the sun or use very bright lights in the morning. Sleep experts recommend that, if you have problems falling asleep, you should get an hour of exposure to morning sunlight and turn down the lights before bedtime.
  12. Don’t lie in bed awake. If you find yourself still awake after staying in bed for more than twenty minutes or if you are starting to feel anxious or worried, get up and do some relaxing activity until you feel sleepy. The anxiety of not being able to sleep can make it harder to fall asleep.

Chapter 15: Sleep and Society

  • A hundred years ago, less than 2 percent of the population in the United States slept six hours or less a night. Now, almost 30 percent of American adults do
  • More than 65 percent of the US adult population fail to obtain the recommended seven to nine hours of sleep each night during the week
  • In the UK and Japan, for example, 39 and 66 percent, respectively, of all adults report sleeping fewer than seven hours
  • Importantly, many of these individuals do not report wanting or needing less sleep
  • Rather than a meager 30 percent of adults getting eight hours of sleep or more on average, almost 60 percent of these individuals attempt to “binge” on eight or more hours. Each weekend, vast numbers of people are desperately trying to pay back a sleep debt they’ve accrued during the week

Sleep in the workplace

  • Sleep deprivation degrades many of the key faculties required for most forms of employment
  • There remains a contrived, yet fortified, arrogance in many business cultures focused on the uselessness of sleep. We glorify the high-powered executive on email until 1:00 a.m., and then in the office by 5:45 a.m.; we laud the airport “warrior” who has traveled through five different time zones on seven flights over the past eight days
  • Certain business leaders mistakenly believe that time on-task equates with task completion and productivity
  • A study across four large US companies found that insufficient sleep cost almost $2,000 per employee per year in lost productivity. That amount rose to over $3,500 per employee in those suffering the most serious lack of sleep
  • Individuals who sleep fewer than seven hours a night on average cause a staggering fiscal cost to their country, compared to employees who sleep more than eight hours each night
Sleep loss cost on global economic
image
  • Insufficient sleep robs most nations of more than 2 percent of their GDP— amounting to the entire cost of each country’s military
  • Numerous employee traits commonly include: creativity, intelligence, motivation, effort, efficiency, effectiveness when working in groups, as well as emotional stability, sociability, and honesty. All of these are systematically dismantled by insufficient sleep
  • 📌

    Sleepy employees are unproductive employees

  • Give participants the ability to choose between work tasks of varying effort, from easy (e.g., listening to voice mails) to difficult (e.g., helping design a complex project that requires thoughtful problem solving and creative planning), and you find that those individuals who obtained less sleep in the preceding days are the same people who consistently select less challenging problems
  • Under-slept employees are not, therefore, going to drive your business forward with productive innovation. Like a group of people riding stationary exercise bikes, everyone looks like they are pedaling, but the scenery never changes
  • The irony that employees miss is that when you are not getting enough sleep, you work less productively and thus need to work longer to accomplish a goal. This means you often must work longer and later into the evening, arrive home later, go to bed later, and need to wake up earlier, creating a negative feedback loop. Why try to boil a pot of water on medium heat when you could do so in half the time on high?
  • People often tell me that they do not have enough time to sleep because they have so much work to do. Without wanting to be combative in any way whatsoever, I respond by informing them that perhaps the reason they still have so much to do at the end of the day is precisely because they do not get enough sleep at night
  • Interestingly, participants in the above studies do not perceive themselves as applying less effort to the work challenge, or being less effective, when they were sleep-deprived, despite both being true
  • Even the simplest daily routines that require slight effort, such as time spent dressing neatly or fashionably for the workplace, have been found to decrease following a night of sleep loss

Traits of a sleepy employee

  • Individuals also like their jobs less when sleep-deprived
  • Under-slept employees are not only less productive, less motivated, less creative, less happy, and lazier, but they are also more unethical
  • Studies in the workplace have found that employees who sleep six hours or less are significantly more deviant and more likely to lie the following day than those who sleep six hours or more
  • The less an individual sleeps, the more likely they are to create fake receipts and reimbursement claims, and the more willing to lie to get free raffle tickets
  • Under-slept employees are more likely to blame other people in the workplace for their own mistakes, and even try to take credit for other people’s successful work
Social loafing

Ethical deviance linked to a lack of sleep also weasels its way onto the work stage in a different guise, called social loafing. The term refers to someone who, when group performance is being assessed, decides to exert less effort when working in that group than when working alone. Individuals see an opportunity to slack off and hide behind the collective hard work of others. They complete fewer aspects of the task themselves, and that work tends to be either wrong or of lower quality, relative to when they alone are being assessed. Sleepy employees therefore choose the more selfish path of least resistance when working in teams, coasting by on the disingenuous ticket of social loafing.VI Not only does this lead to lower group productivity, understandably it often creates feelings of resentment and interpersonal aggression among team members

  • Sleepy employees choose the more selfish path of least resistance when working in teams, coasting by on the disingenuous ticket of social loafing. Not only does this lead to lower group productivity, understandably it often creates feelings of resentment and interpersonal aggression among team members.
  • Twenty- to sixty-minute differences between an employee who is honest, creative, innovate, collaborative, and productive and one who is not

CEOs, managers, and leaders

  • Examine the effects of sleep deficiency in CEOs and supervisors, and the story is equally impactful. An ineffective leader within any organization can have manifold trickle-down consequences to the many whom they influence
  • We often think that a good or bad leader is good or bad day after day—a stable trait. Not true. Differences in individual leadership performance fluctuate dramatically from one day to the next, and the size of that difference far exceeds the average difference from one individual leader to another.
  • So what explains the ups and downs of a leader’s ability to effectively lead, day to day? The amount of sleep they are getting is one clear factor.
  • The lower the quality of sleep that the supervisor reported getting from one night to the next accurately predicted poor self-control and a more abusive nature toward employees the following day, as reported by the employees themselves.
  • In the days after a supervisor had slept poorly, the employees themselves, even if well rested, became less engaged in their jobs throughout that day as a consequence. It was a chain-reaction effect, one in which the lack of sleep in that one superordinate person in a business structure was transmitted on like a virus, infecting even wellrested employees with work disengagement and reduced productivity
  • Reinforcing this reciprocity, we have since discovered that under-slept managers and CEOs are less charismatic and have a harder time infusing their subordinate teams with inspiration and drive.
  • Unfortunately for bosses, a sleep-deprived employee will erroneously perceive a well-rested leader as being significantly less inspiring and charismatic than they truly are. One can only imagine the multiplicative consequences to the success of a business if both the leader and the employees are overworked and under-slept

Financial impact

  • Employees also win financially when sleep times increase. Those who sleep more earn more money, on average
  • An hour of extra sleep still returned significantly higher wages in those eastern locations, somewhere in the region of 4 to 5 percent. You may sniff at that return on the investment of sixty minutes of sleep, but it’s not trivial. The average pay raise in the US is around 2.6 percent. Most people are strongly motivated to get that raise, and are upset when they don’t. Imagine almost doubling that pay raise—not by working more hours, but by getting more sleep
  • The fact of the matter is that most people will trade sleep for a higher salary
  • A recent study from Cornell University surveyed hundreds of US workers and gave them a choice between either (1) $80,000 a year, working normal work hours, and getting the chance for around eight hours of sleep, or (2) $140,000 a year, working consistent overtime shifts, and only getting six hours of sleep each night. Unfortunately, the majority of individuals went with the second option of a higher salary and shorter sleep. That’s ironic, considering that you can have both

Sleep-promoting culture

  • Procter & Gamble Co. and Goldman Sachs Group Inc., for example, both offer free “sleep hygiene” courses to their employees. Expensive, high-grade lighting has been installed in some of their buildings to better help workers regulate their circadian rhythms, improving the timed release of melatonin
  • Nike and Google have both adopted a more relaxed approach to work schedules, allowing employees to time their daily work hours to match their individual circadian rhythms and their respective owl and lark chronotype nature
  • The change in mind-set is so radical that these same brand-leading corporations even allow workers to sleep on the job. Littered throughout their corporate headquarters are dedicated relaxation rooms with “nap pods.” Employees can indulge in sleep throughout the workday in these “shh” zones, germinating productivity and creativity while enhancing wellness and reducing absenteeism
  • Sadly, most CEOs and managers still reject the importance of a well-slept employee. They believe such accommodations represent the “soft approach.” But make no mistake: companies like Nike and Google are as shrewd as they are profitable. They embrace sleep due to its proven dollar value
  • NASA discovered Naps as short as twenty-six minutes in length still offered a 34 percent improvement in task performance and more than a 50 percent increase in overall alertness. These results hatched the so-called NASA nap culture throughout terrestrial workers in the organization

Sleep and torture

  • Business is not the only place where sleep deprivation and ethics collide. Governments and militaries bare a more disgraceful blemish
  • Some governments do not share these same moral values. They will sleep deprive individuals against their will under the auspice of torture
  • Many modern-day torture methods are deviously designed to leave no evidence of physical assault. Sleep deprivation epitomizes this goal and, at the time of writing this book, is still used for interrogation by countries, including Myanmar, Iran, Iraq, the United States, Israel, Egypt, Libya, Pakistan, Saudi Arabia, Tunisia, and Turkey
  • In the context of interrogation, sleep deprivation is ill designed for the purpose of obtaining accurate, and thus actionable, intelligence. A lack of sleep, even moderate amounts, degrades every mental faculty necessary to obtain valid information. This includes the loss of accurate memory recall, emotional instability that prevents logical thought, and even basic verbal comprehension
  • Sleep deprivation increases deviant behavior and causes higher rates of lying and dishonesty
  • One night of sleep deprivation will double or even quadruple the likelihood that an otherwise upstanding individual will falsely confess to something they have not done. You can, therefore, change someone’s very attitudes, their behavior, and even their strongly held beliefs simply by taking sleep away from them
  • The second and more forceful argument for the abolition of enforced sleep deprivation is the permanent physical and mental harm it inflicts
  • Mentally, long-term sleep deprivation over many days elevates suicidal thoughts and suicide attempts, both of which occur at vastly higher rates in detained prisoners relative to the general population. Inadequate sleep further cultivates the disabling and non-transient conditions of depression and anxiety.
  • Physically, prolonged sleep deprivation increases the likelihood of a cardiovascular event, such as a heart attack or stroke, weakens the immune system in ways that encourage cancer and infection, and renders genitals infertile.
  • Depriving a human of sleep without their willing consent and careful medical care is a barbaric tool of assault, psychologically and biologically. Measured on the basis of mortality impact over the long term, it is on a par with starvation

Sleep and education

  • More than 80 percent of public high schools in the United States begin before 8:15 a.m. Almost 50 percent of those start before 7:20 a.m. School buses for a 7:20 a.m. start time usually begin picking up kids at around 5:45 a.m. As a result, some children and teenagers must wake up at 5:30 a.m., 5:15 a.m., or even earlier, and do so five days out of every seven, for years on end. This is lunacy.
  • Could you concentrate and learn much of anything when you had woken up so early? Keep in mind that 5:15 a.m. to a teenager is not the same as 5:15 a.m. to an adult
  • Could you concentrate and learn anything after having forcefully been woken up at 3:15 a.m., day after day after day? Would you be in a cheerful mood? Would you find it easy to get along with your coworkers and conduct yourself with grace, tolerance, respect, and a pleasant demeanor?
  • Unnecessarily bankrupting the sleep of a teenager could make all the difference in the precarious tipping point between psychological wellness and lifelong psychiatric illness
REM-sleep deprivation study on young adults

Back in the 1960s, when the functions of sleep were still largely unknown, researchers selectively deprived young adults of REM sleep, and thus dreaming, for a week, while still allowing them NREM sleep. The unfortunate study participants spent the entire time in the laboratory with electrodes placed on their heads. At night, whenever they entered into the REM-sleep state, a research assistant would quickly enter the bedroom and wake the subjects up. The blurry-eyed participants then had to do math problems for five to ten minutes, preventing them from falling back into dream sleep. But as soon as the participants did return into REM sleep, the procedure was repeated. Hour after hour, night after night, this went on for an entire week. NREM sleep was left largely intact, but the amount of REM sleep was reduced to a fraction of its regular quantity. It didn’t require all seven nights of dream-sleep deprivation before the mental health effects began to manifest. By the third day, participants were expressing signs of psychosis. They became anxious, moody, and started to hallucinate. They were hearing things and seeing things that were not real. They also became paranoid. Some believed that the researchers were plotting against them in collusive ways—trying to poison them, for example. Others became convinced that the scientists were secret agents, and that the experiment was a thinly veiled government conspiracy of some wicked kind. Only then did scientists realize the rather profound conclusions of the experiment: REM sleep is what stands between rationality and insanity.

  • It didn’t require all seven nights of dream-sleep deprivation before the mental health effects began to manifest. By the third day, participants were expressing signs of psychosis. They became anxious, moody, and started to hallucinate. They were hearing things and seeing things that were not real. They also became paranoid. Some believed that the researchers were plotting against them in collusive ways—trying to poison them, for example. Others became convinced that the scientists were secret agents, and that the experiment was a thinly veiled government conspiracy of some wicked kind.
  • Describe these symptoms to a psychiatrist without informing them of the REM-sleep deprivation context, and the clinician will give clear diagnoses of depression, anxiety disorders, and schizophrenia
  • REM sleep is what stands between rationality and insanity. It is the lack of REM sleep—that critical stage occurring in the final hours of sleep that we strip from our children and teenagers by way of early school start times—that creates the difference between a stable and unstable mental state
  • A century ago, schools in the US started at nine a.m. As a result, 95 percent of all children woke up without an alarm clock
  • No matter what the age, the longer a child slept, the more intellectually gifted they were
  • Children with longer total sleep times develop superior IQ, with brighter children having consistently slept forty to fifty minutes more than those who went on to develop a lower IQ
  • The twin with the longer sleep pattern was superior in their intellectual and educational abilities, with higher scores on standardized tests of reading and comprehension, and a more expansive vocabulary than the twin who was obtaining less sleep
  • Edina, Minnesota. Here, school start times for teenagers were shifted from 7:25 a.m. to 8:30 a.m. More striking than the forty-three minutes of extra sleep that these teens reported getting was the change in academic performance, indexed using a standardized measure called the Scholastic Assessment Test, or SAT. In the year before this time change, the average verbal SAT scores of the top-performing students was a very respectable 605. The following year, after switching to an 8:30 a.m. start time, that score rose to an average 761 for the same top-tier bracket of students. Math SAT scores also improved, increasing from an average of 683 in the year prior to the time change, to 739 in the year after. Add this all up, and you see that investing in delaying school start times—allowing students more sleep and better alignment with their unchangeable biological rhythms—returned a net SAT profit of 212 points. That improvement will change which tier of university those teenagers go to, potentially altering their subsequent life trajectories as a consequence
  • Performance improvements were observed regardless of time of day; however, the most dramatic surges occurred in morning classes
  • Children from lower socioeconomic backgrounds are less likely to be taken to school in a car, in part because their parents often have jobs in the service industry demanding work start times at or before six a.m. Such children therefore rely on school buses for transit, and must wake up earlier than those taken to school by their parents. As a result, those already disadvantaged children become even more so because they routinely obtain less sleep than children from more affluent families. The upshot is a vicious cycle that perpetuates from one generation to the next—a closed-loop system that is very difficult to break out of
  • Research findings have also revealed that increasing sleep by way of delayed school start times wonderfully increases class attendance, reduces behavioral and psychological problems, and decreases substance and alcohol use
  • In addition, later start times beneficially mean a later finish time. This protects many teens from the well-researched “danger window” between three and six p.m., when schools finish but before parents return home. This unsupervised, vulnerable time period is a recognized cause of involvement in crime and alcohol and substance abuse
  • The life expectancy of students increased. The leading cause of death among teenagers is road traffic accidents, and in this regard, even the slightest dose of insufficient sleep can have marked consequences
  • When the Mahtomedi School District of Minnesota pushed their school start time from 7:30 to 8:00 a.m., there was a 60 percent reduction in traffic accidents in drivers sixteen to eighteen years of age. To place that in context, the advent of anti-lock brake technology (ABS)—which prevents the wheels of a car from seizing up under hard braking, allowing the driver to still maneuver the vehicle—reduced accident rates by around 20 to 25 percent
  • School bus schedules and bus unions are a major roadblock thwarting appropriately later school start times, as is the established routine of getting the kids out the door early in the morning so that parents can start work early
  • Data aggregated over the past century from more than 750,000 schoolchildren aged five to eighteen reveal that they are sleeping two hours fewer per night than their counterparts were a hundred years ago

Sleep deficiency and the epidemic of ADHD (attention deficit hyperactivity disorder)

  • Children with this diagnosis are irritable, moodier, more distractible and unfocused in learning during the day, and have a significantly increased prevalence of depression and suicidal ideation.
  • If you make a composite of these symptoms (unable to maintain focus and attention, deficient learning, behaviorally difficult, with mental health instability), and then strip away the label of ADHD, these symptoms are nearly identical to those caused by a lack of sleep.
  • Take an under-slept child to a doctor and describe these symptoms without mentioning the lack of sleep, which is not uncommon, and what would you imagine the doctor is diagnosing the child with, and medicating them for? Not deficient sleep, but ADHD
  • There is more irony here than meets the eye. Most people know the name of the common ADHD medications: Adderall and Ritalin. But few know what these drugs actually are. Adderall is amphetamine with certain salts mixed in, and Ritalin is a similar stimulant, called methylphenidate. Amphetamine and methylphenidate are two of the most powerful drugs we know of to prevent sleep and keep the brain of an adult (or a child, in this case) wide awake. That is the very last thing that such a child needs
  • One example of an undiagnosed sleep disorder is pediatric sleep-disordered breathing, or child obstructive sleep apnea, which is associated with heavy snoring. Overly large adenoids and tonsils can block the airway passage of a child as their breathing muscles relax during sleep
  • The resulting oxygen debt will reflexively force the brain to awaken the child briefly throughout the night so that several full breaths can be obtained, restoring full blood oxygen saturation. However, this prevents the child from reaching and/or sustaining long periods of valuable deep NREM sleep. Their sleep-disordered breathing will impose a state of chronic sleep deprivation, night after night, for months or years on end.
  • As the state of chronic sleep deprivation builds over time, the child will look ever more ADHD-like in temperament, cognitively, emotionally, and academically
  • Those children who are fortunate to have the sleep disorder recognized, and who have their tonsils removed, more often than not prove that they do not have ADHD. In the weeks after the operation, a child’s sleep recovers, and with it, normative psychological and mental functioning in the months ahead. Their “ADHD” is cured
  • Based on recent surveys and clinical evaluations, we estimate that more than 50 percent of all children with an ADHD diagnosis actually have a sleep disorder, yet a small fraction know of their sleep condition and its ramifications
  • Over 70 percent of parents believing their child gets enough sleep, when in reality, less than 25 percent of children aged eleven to eighteen actually obtain the necessary amount
  • When sleep is abundant, minds flourish. When it is deficient, they don’t

Sleep and health care

  • If you are about to receive medical treatment at a hospital, you’d be well advised to ask the doctor: “How much sleep have you had in the past twenty-four hours?” The doctor’s response will determine, to a statistically provable degree, whether the treatment you receive will result in a serious medical error, or even death.
  • Nurses and doctors work long, consecutive hours, and none more so than doctors during their resident training years
Story of William Steward Halsted

All of us know that nurses and doctors work long, consecutive hours, and none more so than doctors during their resident training years. Few people, however, know why. Why did we ever force doctors to learn their profession in this exhausting, sleepless way? The answer originates with the esteemed physician William Stewart Halsted, MD, who was also a helpless drug addict. Halsted founded the surgical training program at Johns Hopkins Hospital in Baltimore, Maryland, in May 1889. As chief of the Department of Surgery, his influence was considerable, and his beliefs about how young doctors must apply themselves to medicine, formidable. There was to be a six-year residency, quite literally. The term “residency” came from Halsted’s belief that doctors must live in the hospital for much of their training, allowing them to be truly committed in their learning of surgical skills and medical knowledge. Fledgling residents had to suffer long, consecutive work shifts, day and night. To Halsted, sleep was a dispensable luxury that detracted from the ability to work and learn. Halsted’s mentality was difficult to argue with, since he himself practiced what he preached, being renowned for a seemingly superhuman ability to stay awake for apparently days on end without any fatigue. But Halsted had a dirty secret that only came to light years after his death, and helped explain both the maniacal structure of his residency program and his ability to forgo sleep. Halsted was a cocaine addict. It was a sad and apparently accidental habit, one that started years before his arrival at Johns Hopkins. Early in his career, Halsted was conducting research on the nerve-blocking abilities of drugs that could be used as anesthetics to dull pain in surgical procedures. One of those drugs was cocaine, which prevents electrical impulse waves from shooting down the length of the nerves in the body, including those that transmit pain. Addicts of the drug know this all too well, as their nose, and often their entire face, will become numb after snorting several lines of the substance, almost like having been injected with too much anesthetic by an overly enthusiastic dentist. Working with cocaine in the laboratory, it didn’t take long before Halsted was experimenting on himself, after which the drug gripped him in an ceaseless addiction. If you read Halsted’s academic report of his research findings in the New York Medical Journal from September 12, 1885, you’d be hard pressed to comprehend it. Several medical historians have suggested that the writing is so discombobulated and frenetic that he undoubtedly wrote the piece when high on cocaine. Colleagues noticed Halsted’s odd and disturbing behaviors in the years before and after his arrival at Johns Hopkins. This included excusing himself from the operating theater while he was supervising residents during surgical procedures, leaving the young doctors to complete the operation on their own. At other times, Halsted was not able to operate himself because his hands were shaking so much, the cause of which he tried to pass off as a cigarette addiction. Halsted was now in dire need of help. Ashamed and nervous that his colleagues would discover the truth, he entered a rehabilitation clinic under his first and middle name, rather than using his surname. It was the first of many unsuccessful attempts at kicking his habit. For one stay at Butler Psychiatric Hospital in Providence, Rhode Island, Halsted was given a rehabilitation program of exercise, a healthy diet, fresh air, and, to help with the pain and discomfort of cocaine withdrawal, morphine. Halsted subsequently emerged from the “rehabilitation” program with both a cocaine addiction and a morphine addiction. There were even stories that Halsted would inexplicably send his shirts to be laundered in Paris, and they would return in a parcel containing more than just pure-white shirts. Halsted inserted his cocaine-infused wakefulness into the heart of Johns Hopkins’s surgical program, imposing a similarly unrealistic mentality of sleeplessness upon his residents for the duration of their training. The exhausting residency program, which persists in one form or another throughout all US medical schools to this day, has left countless patients hurt or dead in its wake—and likely residents, too. That may sound like an unfair charge to level considering the wonderful, lifesaving work our committed and caring young doctors and medical staff perform, but it is a provable one.

  • Halsted inserted his cocaine-infused wakefulness into the heart of Johns Hopkins’s surgical program, imposing a similarly unrealistic mentality of sleeplessness upon his residents for the duration of their training.
  • The exhausting residency program, which persists in one form or another throughout all US medical schools to this day, has left countless patients hurt or dead in its wake—and likely residents, too
  • Many medical schools used to require residents to work thirty hours. You may think that’s short, since I’m sure you work at least forty hours a week. But for residents, that was thirty hours all in one go. Worse, they often had to do two of these thirty-hour continuous shifts within a week, combined with several twelve-hour shifts scattered in between
  • Residents working a thirty-hour-straight shift will commit 36 percent more serious medical errors, such as prescribing the wrong dose of a drug or leaving a surgical implement inside of a patient, compared with those working sixteen hours or less.
  • Additionally, after a thirty-hour shift without sleep, residents make a whopping 460 percent more diagnostic mistakes in the intensive care unit than when well rested after enough sleep
  • Throughout the course of their residency, one in five medical residents will make a sleeplessrelated medical error that causes significant, liable harm to a patient.
  • One in twenty residents will kill a patient due to a lack of sleep.
  • After a thirty-hour continuous shift, exhausted residents are 73 percent more likely to stab themselves with a hypodermic needle or cut themselves with a scalpel, risking a blood-born infectious disease, compared to their careful actions when adequately rested
  • When a sleep-deprived resident finishes a long shift, their chances of being involved in a motor vehicle accident are increased by 168 percent because of fatigue
  • If you are a patient under the knife of an attending physician who has not been allowed at least a six-hour sleep opportunity the night prior, there is a 170 percent increased risk of that surgeon inflicting a serious surgical error on you, such as organ damage or major hemorrhaging, relative to the superior procedure they would conduct when they have slept adequately
  • If you are about to undergo an elective surgery, you should ask how much sleep your doctor has had and, if it is not to your liking, you may not want to proceed.
  • No amount of years on the job helps a doctor “learn” how to overcome a lack of sleep and develop resilience
  • Accreditation Council for Graduate Medical Education—the elite board of high-powered physicians that dictates the American residency training structure—stated that data proving the dangers of insufficient sleep had only been gathered in residents in their first year of the program. As a result, they felt there was no evidence to justify a change for residents in years two to five—as if getting past the twelve-month point in a medical residency program magically confers immunity against the biological and psychological effects of sleep deprivation—effects that these same individuals had previously been so provably vulnerable to just months before. This entrenched pomposity, prevalent in so many senior-driven, dogmatic institutional hierarchies, has no place in medical practice in my opinion as a scientist intimate with the research data. Those boards must disabuse themselves of the we-suffered-through-sleep- deprivation-and-you-should-too mentality when it comes to training, teaching, and practicing medicine.
  • Many of western European medical programs, such as in the UK and Sweden, rank among the top ten countries for most medical practice health outcomes, while the majority of US institutes rank somewhere between eighteenth and thirty-second
  • Several pilot studies in the US have shown that when you limit residents to no more than a sixteen-hour shift, with at least an eight-hour rest opportunity before the next shift, the number of serious medical errors made—defined as causing or having the potential to cause harm to a patient—drops by over 20 percent. Furthermore, residents made 400 to 600 percent fewer diagnostic errors to begin with

  • “I’ve always loathed the necessity of sleep. Like death, it puts even the most powerful men on their backs.” — Frank Underwood
  • Consider the infamous reactor meltdown at the Chernobyl nuclear power station on April 26, 1986. The radiation from the disaster was one hundred times more powerful than the atomic bombs dropped in World War II. It was the fault of sleep-deprived operators working an exhaustive shift, occurring, without coincidence, at one a.m
  • We can also recount the Exxon Valdez oil tanker that ran aground on Bligh Reef in Alaska on March 24, 1989, breaching its hull. An estimated 10 million to 40 million gallons of crude oil spilled across a 1,300-mile range of the surrounding shoreline. Left dead were more than 500,000 seabirds, 5,000 otters, 300 seals, over 200 bald eagles, and 20 orca whales. The coastal ecosystem has never recovered. Early reports suggested that the captain was inebriated while navigating the vessel. Later, however, it was revealed that the sober captain had turned over command to his third mate on deck, who had only slept six out of the previous forty-eight hours, causing him to make the cataclysmic navigational error

Chapter 16: A New Vision for Sleep in the Twenty-First Century

What are the solutions for sleep change?

  • First, we must understand why the problem of deficient sleep seems to be so resistant to change, and thus persists and grows worse. Second, we must develop a structured model for effecting change at every possible leverage point we can identify

Individual transformation

  • Increasing sleep for an individual can be achieved through both passive methods, which require no effort from the individual and are thus preferable, and active methods, which do
  • The intrusion of technology into our homes and bedrooms is claimed by many of my research colleagues to be robbing us of precious sleep
  • We will never put that technological genie back into its bottle, nor do we need to. Instead, we can use this powerful tool to our advantage
  • If something increased your sleep amount by just fifteen to twenty minutes each night, the science indicates that it would make a significant difference across the life span and save trillions of dollars within the global economy at the population level, to name but two benefits

Technological solutions for better sleep at home

  • There will be commercially available, affordable devices that track an individual’s sleep and circadian rhythm with high accuracy. When that happens, we can marry these individual sleep trackers with the revolution of in-home networked devices like thermostats and lighting.
  1. Use sleep tracker + AI to control thermostat → set ideal temperature for sleep
    1. Such devices could compare the sleep of each family member in each separate bedroom with the temperature sensed in each room by the thermostat. Using common machine-learning algorithms applied over time, we should be able to intelligently teach the home thermostat what the thermal sweet spot is for each occupant in each bedroom, based on the biophysiology calculated by their sleep-tracking device (perhaps splitting the difference when there are two or more individuals per room). Granted there are many different factors that make for a good or bad night of sleep, but temperature is very much one of them. Better still, we could program a natural circadian lull and rise in temperature across the night that is in harmony with each body’s expectations, rather than the constant nighttime temperature set in most homes and apartments. Over time, we could intelligently curate a tailored thermal sleep environment that is personalized to the circadian rhythms of each individual occupant of each bedroom, departing from the unhelpful non-varying thermal backdrop that plagues the sleep of most people using standard home thermostats. Both these changes require no effort from an individual, and should hasten the speed of sleep onset, increase total sleep time, and even deepen NREM-sleep quality for all household members
  2. Use sleep tracker + AI to control light → set ideal light exposure for better sleep
    1. The second passive solution concerns electric light. Many of us suffer from overexposure to nighttime light, particularly blue-dominant LED light from our digital devices. This evening digital light suppresses melatonin and delays our sleep timing. What if we can turn that problem into a solution? Soon, we should be able to engineer LED bulbs with filters that can vary the wavelength of light that they emit, ranging from warm yellow colors less harmful to melatonin, to strong blue light that powerfully suppresses it. Paired with sleep trackers that can accurately characterize our personal biological rhythms, we can install these new bulbs throughout a home, all connected to the home network. The lightbulbs (and even other networked LED-screen devices, such as iPads) would be instructed to gradually dial down the harmful blue light in the home as the evening progresses, based on an individual’s (or set of individuals’) natural sleep-wake pattern. We could do this dynamically and seamlessly as individuals move from one room to the next in real time. Here again we can intelligently split the difference on the fly based on the biophysiological mix of whoever is in the room. In doing so, the users’ own brains and bodies, measured and translated through the wearables to the networked home, would synergistically regulate light and thus melatonin release that promotes, rather than impedes, optimal regulation of sleep for one and all. It is a vision of personalized sleep medicine. Come the morning, we can reverse this trick. We can now saturate our indoor environments with powerful blue light that shuts off any lingering melatonin. This will help us wake up faster, more alert, and with a brighter mood, morning after morning

Other use cases

  • Cars can adopt these same lighting solutions to help manipulate alertness during morning commutes. Some of the highest rates of drowsy-driving accidents occur during mornings, especially early mornings. What if car cockpits could be bathed in blue light during early-morning commutes?
  • Special NASA bulbs. The bulbs were to be installed in the space station to bathe the astronauts in a much more Earth-like cycle of twenty-four-hour light and dark. With regulated environmental light came a superior regulation of the astronauts’ biological melatonin rhythms, including their sleep, thereby reducing operations errors associated with fatigue. I must admit that the development cost of each lightbulb was in the neighborhood of $300,000. But numerous companies are now hard at work constructing similar bulbs for a fraction of that cost
  • Sleep analytics
    • With wearables that accurately track our slumber fast emerging, we can apply this same approach to sleep. Harnessing smartphones as a central hub to gather an individual’s health data from various sources—physical activity (such as number of steps or minutes and intensity of exercise), light exposure, temperature, heart rate, body weight, food intake, work productivity, or mood—we show each individual how their own sleep is a direct predictor of their own physical and mental health. It’s likely that, if you wore such a device, you would find out that on the nights you slept more you ate less food the next day, and of a healthy kind; felt brighter, happier, and more positive; had better relationship interactions; and accomplished more in less time at work. Moreover, you would discover that during months of the year when you were averaging more sleep, you were sick less; your weight, blood pressure, and medication use were all lower; and your relationship or marriage satisfaction, as well as sex life, were better
  • Sleep predictalytics
    • To explain the term, let me go back to the smoking example. There are efforts to create predictalytics apps that start with you taking a picture of your own face with the camera of your smartphone. The app then asks you how many cigarettes you smoke on average a day. Based on scientific data that understand how smoking quantity impacts outward health features such as bags under your eyes, wrinkles, psoriasis, thinning hair, and yellowed teeth, the app predictively modifies your face on the assumption of your continued smoking, and does so at different future time points: one year, two years, five years, ten years. The very same approach could be adopted for sleep, but at many different levels: outward appearance as well as inward brain and body health. For example, we could show individuals their increasing risk (albeit non-deterministic) of conditions such as Alzheimer’s disease or certain cancers if they continue sleeping too little. Men could see projections on how much their testicles will shrink or their testosterone level will drop should their sleep neglect continue. Similar risk predictions could be made for gains in body weight, diabetes, or immune impairment and infection. Another example involves offering individuals a prediction of when they should or should not get their flu shot based on sleep amount in the week prior

Educational change

  • We receive 0 educational materials or information about sleep during our schooling years. Compared to information about diet, exercise, drugs, alcohol, and safe sex

Organizational change

  • The giant insurance company Aetna, which has almost fifty thousand employees, has instituted the option of bonuses for getting more sleep, based on verified sleep-tracker data. As Aetna chairman and CEO Mark Bertolini described, “Being present in the workplace and making better decisions has a lot to do with our business fundamentals.” He further noted, “You can’t be prepared if you’re half asleep.”
  • The return on the sleep investment in terms of productivity, creativity, work enthusiasm, energy, efficiency—not to mention happiness, leading to people wanting to work at your institution, and stay—is undeniable
  • I would suggest a “sleep credit system,” with sleep time being exchanged for either financial bonuses or extra vacation days. There would be at least one proviso: the sleep credit system would not simply be calculated on total hours clocked during one week or one month. As we have learned, sleep continuity— consistently getting seven to nine hours of sleep opportunity each night, every night, without running a debt during the week and hoping to pay it off by binge-sleeping at the weekend—is just as important as total sleep time if you are to receive the mental and physical health benefits of sleep. Thus, your “sleep credit score” would be calculated based on a combination of sleep amount and night-to-night sleep continuity
  • Flexible work schedule. Rather than required hours with relatively hard boundaries (i.e., the classic nine to five), businesses need to adapt a far more tapered vision of hours of operation, one that resembles a squished inverted-U shape. Everyone would be present during a core window for key interactions—say, twelve to three p.m. Yet there would be flexible tail ends either side to accommodate all individual chronotypes. Owls could start work late (e.g., noon) and continue into the evening, giving their full force of mental capacity and physical energy to their jobs. Larks can likewise do so with early start and finish times, preventing them from having to coast through the final hours of the “standard” workday with inefficient sleepiness
  • There are secondary benefits. Take rush-hour traffic as just one example, which would be lessened in both the morning and evening phases. The indirect cost savings of time, money, and stress would not be trivial

Sleep in medicine change

  • The less sleep you have had, or the more fragmented your sleep, the more sensitive you are to pain of all kinds.
  • The most common place where people experience significant and sustained pain is often the very last place they can find sound sleep: a hospital. The problems are especially compounded in the intensive care unit, where the most severely sick (i.e., those most in need of sleep’s help) are cared for. Incessant beeping and buzzing from equipment, sporadic alarms, and frequent tests prevent anything resembling restful or plentiful sleep for the patient
  • As it turns out, 50 to 80 percent of all intensive care alarms are unnecessary or ignorable by staff
  • Upset by the noisy, unfamiliar ICU environment, sleep takes longer to initiate, is littered with awakenings, is shallower in depth, and contains less overall REM sleep. Worse still, doctors and nurses consistently overestimate the amount of sleep they think patients obtain in intensive care units, relative to objectively measured sleep in these individuals. All told, the sleep environment, and thus sleep amount, of a patient in this hospital environment is entirely antithetical to their convalescence
  • Improving sleep conditions for patients would not only reduce drug doses, it would also boost their immune system
  • Nobody wants to be in the hospital any longer than is absolutely necessary. Hospital administrators feel likewise. Sleep can help
  • We can start by removing any equipment and alarms that are not necessary for any one patient.
  • Next, we must educate doctors, nurses, and hospital administrations on the scientific health benefits of sound sleep, helping them realize the premium we must place on patients’ slumber.
  • We can also ask patients about their regular sleep schedules on the standard hospital admission form, and then structure assessments and tests around their habitual sleep-wake rhythms as much as possible. When I’m recovering from an appendicitis operation, I certainly don’t want to be woken up at 6:30 a.m. when my natural rise time is 7:45 a.m
  • To keep a preterm baby alive and healthy is a perilous challenge. Instability of body temperature, respiratory stress, weight loss, and high rates of infection can lead to cardiac instability, neurodevelopment impairments, and death. At this premature stage of life, infants should be sleeping the vast majority of the time, both day and night
  • However, in most neonatal intensive care units, strong lighting will often remain on throughout the night, while harsh electric overhead light assaults the thin eyelids of these infants during the day. Imagine trying to sleep in constant light for twenty-four hours a day

Societal change

  • At the highest levels, we need better public campaigns educating the population about sleep
  • We spend a tiny fraction of our transportation safety budget warning people of the dangers of drowsy driving compared with the countless campaigns and awareness efforts regarding accidents linked to drugs or alcohol. Governments could save hundreds of thousands of lives each year if they mobilized such a campaign
  • Health insurance companies could approve valid commercial sleep-tracking devices that individuals commonly own. You, the individual, could then upload your sleep credit score to your health-care provider profile
  • Even with lower insurance paid by the individual, health insurance companies would still gain, as it would significantly decrease the cost burden of their insured individuals, allowing for greater profit margins. Everyone wins.
  • Of course, just like a gym membership, some people will start off adhering to the regime but then stop, and some may look for ways to bend or play the system regarding accurate sleep assessment. However, even if only 50 to 60 percent of individuals truly increase their sleep amount, it could save tens or hundreds of millions of dollars in terms of health costs—not to mention hundreds of thousands of lives

Conclusion

This silent sleep loss epidemic is the greatest public health challenge we face in the twenty-first century in developed nations. If we wish to avoid the suffocating noose of sleep neglect, the premature death it inflicts, and the sickening health it invites, a radical shift in our personal, cultural, professional, and societal appreciation of sleep must occur