Why We Sleep (Kindle highlights)

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. Short sleeping increases the likelihood of your coronary arteries becoming blocked and brittle, setting you on a path toward cardiovascular disease, stroke, and congestive heart failure. (p. 3)
It is disquieting to learn that vehicular accidents caused by drowsy driving exceed those caused by alcohol and drugs combined. (p. 5)
Yet sleep has persisted. Heroically so. Indeed, every species studied to date sleeps. (p. 6)
Dreaming provides a unique suite of benefits to all species fortunate enough to experience it, humans included. Among these gifts are a consoling neurochemical bath that mollifies painful memories and a virtual reality space in which the brain melds past and present knowledge, inspiring creativity. (p. 7)
A balanced diet and exercise are of vital importance, yes. But we now see sleep as the preeminent force in this health trinity. The physical and mental impairments caused by one night of bad sleep dwarf those caused by an equivalent absence of food or exercise. (p. 8)
Sleep is the single most effective thing we can do to reset our brain and body health each day. (p. 8)
The first was that humans, like de Mairan’s heliotrope plants, generated their own endogenous circadian rhythm in the absence of external light from the sun. (p. 16)
The second unexpected—and more profound—result was that their reliably repeating cycles of wake and sleep were not precisely twenty-four hours in length, but consistently and undeniably longer than twenty-four hours. (p. 16)
The light of the sun methodically resets our inaccurate internal timepiece each and every day, “winding” us back to precisely, not approximately, twenty-four hours. (p. 17)
We have now determined that the average duration of a human adult’s endogenous circadian clock runs around twenty-four hours and fifteen minutes in length. (p. 17)
Although the temperature drop helps to initiate sleep, the temperature change itself will rise and fall across the twenty-four-hour period regardless of whether you are awake or asleep. (p. 20)
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. (p. 21)
Melatonin simply provides the official instruction to commence the event of sleep, but does not participate in the sleep race itself. (p. 23)
For every day you are in a different time zone, your suprachiasmatic nucleus can only readjust by about one hour. (p. 25)
You may have noticed that it feels harder to acclimate to a new time zone when traveling eastward than when flying westward. (p. 25)
The longer you are awake, the more adenosine will accumulate. (p. 27)
One consequence of increasing adenosine in the brain is an increasing desire to sleep. (p. 27)
By hijacking and occupying these receptors, caffeine blocks the sleepiness signal normally communicated to the brain by adenosine. (p. 28)
Caffeine has an average half-life of five to seven hours. (p. 28)
Across the night, sleep lifts the heavy weight of sleep pressure, lightening the adenosine load. After approximately eight hours of healthy sleep in an adult, the adenosine purge is complete. (p. 33)
First, 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. Second, 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. (p. 35)
Even sunlight coming through thick cloud on a rainy day is powerful enough to help reset our biological clocks. (p. 37)
Kleitman and Aserinsky further demonstrated that 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. (p. 42)
NREM sleep received further dissection in the years thereafter, being subdivided into four separate stages, unimaginatively named NREM stages 1 to 4 (we sleep researchers are a creative bunch), 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. (p. 42)
In the first half of the night, the vast majority of our ninety-minute cycles are consumed by deep NREM sleep, and very little REM sleep, as can be seen in cycle 1 of the figure above. But as we transition through into the second half of the night, this seesaw balance shifts, with most of the time dominated by REM sleep, with little, if any, deep NREM sleep. (p. 44)
We have no scientific consensus as to why our sleep (and that of all other mammals and birds) cycles in this repeatable but dramatically asymmetric pattern, though a number of theories exist. (p. 44)
As we will discover in chapter 6, a 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. (p. 45)
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. (p. 50)
For these reasons, REM sleep has also been called paradoxical sleep: a brain that appears awake, yet a body that is clearly asleep. (p. 52)
When it comes to information processing, think of the wake state principally as reception (experiencing and constantly learning the world around you), NREM sleep as reflection (storing and strengthening those raw ingredients of new facts and skills), and REM sleep as 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). (p. 53)
The brain paralyzes the body so the mind can dream safely. (p. 54)
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;I fish, from small perch to the largest sharks;II amphibians, such as frogs; and reptiles, such as turtles, Komodo dragons, and chameleons. (p. 56)
How “old” does this make sleep? Worms emerged during the Cambrian explosion: at least 500 million years ago. (p. 57)
We have discovered that the very simplest forms of unicellular organisms that survive for periods exceeding twenty-four hours, such as bacteria, have active and passive phases that correspond to the light-dark cycle of our planet. (p. 57)
Sleep is of ancient origin. It appeared with the very earliest forms of planetary life. (p. 57)
Total amount of time is one of the most conspicuous differences in how organisms sleep. (p. 58)
One evolutionary function that demands more sleep is the need to service an increasingly complex nervous system. (p. 58)
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. (p. 59)
Only birds and mammals, which appeared later in the evolutionary timeline of the animal kingdom, have full-blown REM sleep. (p. 60)
Most of our assessments to date have not discovered REM sleep—or at least what many sleep scientists would believe to be true REM sleep—in aquatic mammals. (p. 60)
When a theme repeats in evolution, and independently across unrelated lineages, it often signals a fundamental need. (p. 62)
That humans (and all other species) can never “sleep back” that which we have previously lost is one of the most important take-homes of this book. (p. 64)
Take cetaceans, such as dolphins and whales, for example. Their sleep, of which there is only NREM, can be unihemispheric, meaning they will sleep with half a brain at a time! One half of the brain must always stay awake to maintain life-necessary movement in the aquatic environment. (p. 64)
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. (p. 65)
What becomes clearly apparent when you step back from these details is that modern society has divorced us from what should be a preordained arrangement of biphasic sleep—one that our genetic code nevertheless tries to rekindle every afternoon. (p. 69)
From a prescription written long ago in our ancestral genetic code, the practice of natural biphasic sleep, and a healthy diet, appear to be the keys to a long-sustained life. (p. 71)
From these clues, I offer a theorem: 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. (p. 74)
Autistic individuals show a 30 to 50 percent deficit in the amount of REM sleep they obtain, relative to children without autism. (p. 82)
Prior to birth, and soon after, the challenge for development was to build and add vast numbers of neural highways and interconnections that become a fledgling brain. As we have discussed, REM sleep plays an essential role in this proliferation process, (p. 87)
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. (p. 87)
Deep sleep may be a driving force of brain maturation, not the other way around. (p. 90)
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. (p. 92)
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. (p. 93)
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. (p. 94)
This ingenious biological solution selectively shifts teenagers to a later phase when they can, for several hours, operate independently. (p. 94)
That older adults simply need less sleep is a myth. 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. (p. 95)
It means that elderly individuals fail to connect their deterioration in health with their deterioration in sleep, despite causal links between the two having been known to scientists for many decades. (p. 96)
Even when controlling for factors such as body mass index, gender, race, history of smoking, frequency of exercise, and medications, the lower an older individual’s sleep efficiency score, the higher their mortality risk, the worse their physical health, the more likely they are to suffer from depression, the less energy they report, and the lower their cognitive function, typified by forgetfulness. (p. 97)
Add these things up, and a self-perpetuating cycle ensues wherein many seniors are battling a sleep debt, trying to stay awake later in the evening, inadvertently dozing off earlier, finding it hard to fall or stay asleep at night, only to be woken up earlier than they wish because of a regressed circadian rhythm. (p. 99)
Those who were awake throughout the day became progressively worse at learning, even though their ability to concentrate remained stable (determined by separate attention and response time tests). In contrast, those who napped did markedly better, and actually improved in their capacity to memorize facts. (p. 110)
Sleep six hours or less and you are shortchanging the brain of a learning restoration benefit that is normally performed by sleep spindles. (p. 112)
That sleep sets in motion the process of memory consolidation was recognized long ago, and may be one of the oldest proposed functions of sleep. (p. 112)
If you were a participant in such a study, and the only information I had was the amount of deep NREM sleep you had obtained that night, I could predict with high accuracy how much you would remember in the upcoming memory test upon awakening, even before you took it. That’s how deterministic the link between sleep and memory consolidation can be. (p. 114)
Even daytime naps as short as twenty minutes can offer a memory consolidation advantage, so long as they contain enough NREM sleep. (p. 115)
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. (p. 121)
Sleep was far more intelligent than we had once imagined. (p. 121)
My real-world hope is to develop accurate methods for selectively weakening or erasing certain memories from an individual’s memory library when there is a confirmed clinical need, such as in trauma, drug addiction, or substance abuse. (p. 122)
Practice does not make perfect. It is practice, followed by a night of sleep, that leads to perfection. (p. 126)
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. (p. 132)
No facet of the human body is spared the crippling, noxious harm of sleep loss. We are, as you will see, socially, organizationally, economically, physically, behaviorally, nutritionally, linguistically, cognitively, and emotionally dependent upon sleep. (p. 133)
Ten days of six hours of sleep a night was all it took to become as impaired in performance as going without sleep for twenty-four hours straight. (p. 136)
When participants were asked about their subjective sense of how impaired they were, they consistently underestimated their degree of performance disability. (p. 137)
After being awake for nineteen hours, people who were sleep-deprived were as cognitively impaired as those who were legally drunk. (p. 138)
The recycle rate of a human being is around sixteen hours. 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. Finally, the human mind cannot accurately sense how sleep-deprived it is when sleep-deprived. (p. 140)
Drowsy driving alone is worse than driving drunk. (p. 140)
If you are drowsy while driving, please, please stop. It is lethal. (p. 142)
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. But in the subsequent studies that Dinges and many other researchers (myself included) have performed, neither naps nor caffeine can salvage more complex functions of the brain, including learning, memory, emotional stability, complex reasoning, or decision-making. (p. 144)
“The number of people who can survive on five hours of sleep or less without any impairment, expressed as a percent of the population, and rounded to a whole number, is zero.” (p. 145)
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. (p. 146)
Rather, the under-slept brain swings excessively to both extremes of emotional valence, positive and negative. (p. 148)
I am suggesting that sleep disruption remains a neglected factor contributing to the instigation and/or maintenance of numerous psychiatric illnesses. (p. 150)
Those few memories you are able to learn while sleep-deprived are forgotten far more quickly in the hours and days thereafter. (p. 154)
The two most feared diseases throughout developed nations are dementia and cancer. Both are related to inadequate sleep. (p. 157)
A lack of sleep is fast becoming recognized as a key lifestyle factor determining whether or not you will develop Alzheimer’s disease. (p. 157)
Without sufficient sleep, amyloid plaques build up in the brain, especially in deep-sleep-generating regions, attacking and degrading them. (p. 161)
Take away the bedrock of sleep, or weaken it just a little, and careful eating or physical exercise become less than effective, as we shall see. (p. 164)
The shorter your sleep, the shorter your life. (p. 164)
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. (p. 165)
In the first of these studies, 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. (p. 170)
Inadequate sleep is the perfect recipe for obesity: greater calorie intake, lower calorie expenditure. (p. 175)
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. (p. 175)
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 high-calorie foods), decrease feelings of food satisfaction after eating, and prevent effective weight loss when dieting. (p. 178)
Sleep fights against infection and sickness by deploying all manner of weaponry within your immune arsenal, cladding you with protection. When you do fall ill, the immune system actively stimulates the sleep system, demanding more bed rest to help reinforce the war effort. (p. 181)
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. (p. 184)
If increasing your risk for developing Alzheimer’s disease, cancer, diabetes, depression, obesity, hypertension, and cardiovascular disease weren’t sufficiently disquieting, chronic sleep loss will erode the very essence of biological life itself: your genetic code and the structures that encapsulate it. (p. 186)
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. They were, in effect, mind reading, or should I say, dream reading. (p. 198)
This was the theory of overnight therapy. It postulated that the process of REM-sleep dreaming accomplishes two critical goals: (1) sleeping to remember the details of those valuable, salient experiences, integrating them with existing knowledge and putting them into autobiographical perspective, yet (2) sleeping to forget, or dissolve, the visceral, painful emotional charge that had previously been wrapped around those memories. (p. 208)
Cartwright had shown that 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. (p. 211)
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. (p. 213)
Upon awakenings from NREM sleep, participants did not appear to be especially creative, solving few of the anagram puzzles. But it was a different story when I woke them up out of REM sleep, from the dreaming phase. Overall, 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! (p. 224)
Overall, 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! (p. 224)
Solutions seemed more effortless when the brain was being bathed by the afterglow of dream sleep. (p. 224)
When awake, we see only a narrow set of all possible memory interrelationships. The opposite is true, however, when we enter the dream state and start looking through the other (correct) end of the memory-surveying telescope. Using that wide-angle dream lens, we can apprehend the full constellation of stored information and their diverse combinatorial possibilities, all in creative servitude. (p. 226)
REM sleep is capable of creating abstract overarching knowledge and super-ordinate concepts out of sets of information. (p. 228)
REM sleep is especially dominant during this early-life window, and it is that REM sleep that plays a critical role in the development of language, we believe. (p. 228)
Scientists had gained objective, brain-based proof that lucid dreamers can control when and what they dream while they are dreaming. (p. 233)
There is nothing pathological about sleepwalking or sleep talking. They are common in the adult population, and even more common in children. (p. 239)
Insomnia is the opposite: (i) suffering from an inadequate ability to generate sleep, despite (ii) allowing oneself the adequate opportunity to get sleep. (p. 241)
All of us will experience difficulty sleeping every now and then, which may last just one night or several. That is normal. (p. 242)
It is this set of features of sleep paralysis that we now believe explains a large majority of alien abduction claims. (p. 248)
Soon after turning forty-two years old, 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. It is one of the most mysterious conditions in the annals of medicine, and it has taught us a shocking lesson: a lack of sleep will kill a human being. (p. 255)
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. (p. 263)
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. (p. 264)
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. (p. 268)
A good start is to create lowered, dim light in the rooms where you spend your evening hours. Avoid powerful overhead lights. (p. 270)
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. (p. 270)
Saying that alcohol is a sedative often confuses people, as alcohol in moderate doses helps individuals liven up and become more social. How can a sedative enliven you? The answer comes down to the fact that your increased sociability is caused by sedation of one part of your brain, the prefrontal cortex, early in the timeline of alcohol’s creeping effects. (p. 271)
This is your brain slipping into sedation. Your desire and ability to remain conscious are decreasing, and you can let go of consciousness more easily. I am very deliberately avoiding the term “sleep,” however, because sedation is not sleep. Alcohol sedates you out of wakefulness, but it does not induce natural sleep. (p. 271)
First, alcohol fragments sleep, littering the night with brief awakenings. Alcohol-infused sleep is therefore not continuous and, as a result, not restorative. (p. 271)
Second, alcohol is one of the most powerful suppressors of REM sleep that we know of. (p. 272)
What we do know is that sleep has not finished tending to those newly planted memories by night 3. (p. 274)
Nightly alcohol will disrupt your sleep, and the annoying advice of abstinence is the best, and most honest, I can offer. (p. 275)
Your nocturnal melatonin levels are therefore controlled not only by the loss of daylight at dusk, but also the drop in temperature that coincides with the setting sun. Environmental light and temperature therefore synergistically, though independently, dictate nightly melatonin levels and sculpt the ideal timing of sleep. (p. 275)
It is no evolutionary coincidence that we humans have developed the pre-bed ritual of splashing water on one of the most vascular parts of our bodies—our face, using one of the other highly vascular surfaces—our hands. (p. 276)
A bedroom temperature of around 65 degrees Fahrenheit (18.3°C) is ideal for the sleep of most people, assuming standard bedding and clothing. (p. 277)
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. Consequently, you fall asleep more quickly because your core is colder. Hot baths prior to bed can also induce 10 to 15 percent more deep NREM sleep in healthy adults. (p. 279)
Using the snooze feature means that you will repeatedly inflict that cardiovascular assault again and again within a short span of time. (p. 280)
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. (p. 280)
Sleeping pills, old and new, target the same system in the brain that alcohol does—the receptors that stop your brain cells from firing—and are thus part of the same general class of drugs: sedatives. Sleeping pills effectively knock out the higher regions of your brain’s cortex. (p. 282)
Future versions of such drugs may offer meaningful sleep improvements, but for now the scientific data on prescription sleeping pills suggests that they may not be the answer to returning sound sleep to those struggling to generate it on their own. (p. 284)
Should similar findings continue to emerge, including in humans, pharmaceutical companies may have to acknowledge that, although users of sleeping pills may fall asleep nominally faster at night, they should expect to wake up with few(er) memories of yesterday. (p. 285)
Kripke discovered that individuals using prescription sleep medications are significantly more likely to die and to develop cancer than those who do not. (p. 286)
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. (p. 287)
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. (p. 291)
All twelve suggestions are superb advice, but if you can only adhere to one of these each and every day, make it: 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. (p. 293)
In other words, sleep may have more of an influence on exercise than exercise has on sleep. It is still a clear bidirectional relationship, however, with a significant trend toward increasingly better sleep with increasing levels of physical activity, and a strong influence of sleep on daytime physical activity. (p. 294)
In other words, sleep may have more of an influence on exercise than exercise has on sleep. (p. 294)
It is still a clear bidirectional relationship, however, with a significant trend toward increasingly better sleep with increasing levels of physical activity, and a strong influence of sleep on daytime physical activity. (p. 294)
One brief note of caution regarding physical activity: try not to exercise right before bed. Body temperature can remain high for an hour or two after physical exertion. Should this occur too close to bedtime, it can be difficult to drop your core temperature sufficiently to initiate sleep due to the exercise-driven increase in metabolic rate. Best to get your workout in at least two to three hours before turning the bedside light out (none LED-powered, I trust). (p. 294)
For healthy sleep, the scientific evidence suggests that you should 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. (p. 295)
Under-slept employees are not only less productive, less motivated, less creative, less happy, and lazier, but they are also more unethical. (p. 301)
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. (p. 310)
Numerous counties in several US states have shifted the start of schools to a later hour and their students experienced significantly higher grade point averages. (p. 312)
I hope we can break the parent-to-child transmission of sleep neglect and remove what the exhausted, fatigued brains our youth are so painfully starved of. (p. 316)
There’s simply no evidence-based argument for persisting with the current sleep-anemic model of medical training, one that cripples the learning, health, and safety of young doctors and patients alike. (p. 322)
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 (p. 326)
What if car cockpits could be bathed in blue light during early-morning commutes? (p. 327)
Knowledge alone is not enough. Additional methods are required. (p. 329)
When it comes to the quantified self, it’s the old adage of “seeing is believing” that ensures longer-term adherence to healthy habits. (p. 329)
Sleep appears to be a natural analgesic, and without it, pain is perceived more acutely by the brain, and, most importantly, felt more powerfully by the individual. (p. 336)
In the United States, many health insurance companies provide a financial credit to their members for joining a gym. Considering the health benefits of increased sleep amount, why don’t we institute a similar incentive for racking up more consistent and plentiful slumber? Health insurance companies could approve valid commercial sleep-tracking devices that individuals commonly own. (p. 339)