Why We Sleep: Unlocking the Power of Sleep and Dreams by Matthew Walker

Tips for Healthy Sleep

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.
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.
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.
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.
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.
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.
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.
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.

Chapter 1 : To Sleep

doctors and scientists could not give you a consistent or complete answer as to why we sleep. Consider that we have known the functions of the three other basic drives in life—to eat, to drink, and to reproduce—for many tens if not hundreds of years now. Yet the fourth main biological drive, common across the entire animal kingdom—the drive to sleep—has continued to elude science for millennia.

Addressing the question of why we sleep from an evolutionary perspective only compounds the mystery. No matter what vantage point you take, sleep would appear to be the most foolish of biological phenomena. When you are asleep, you cannot gather food. You cannot socialize. You cannot find a mate and reproduce. You cannot nurture or protect your offspring. Worse still, sleep leaves you vulnerable to predation. Sleep is surely one of the most puzzling of all human behaviors.

Chapter 2 : Caffeine, Jet Lag, and Melatonin

Kleitman and Richardson were to be their own experimental guinea pigs. Loaded with food and water for six weeks and a pair of dismantled, high-standing hospital beds, they took a trip into Mammoth Cave in Kentucky, one of the deepest caverns on the planet—so deep, in fact, that no detectable sunlight penetrates its farthest reaches. It was from this darkness that Kleitman and Richardson were to illuminate a striking scientific finding that would define our biological rhythm as being approximately one day (circadian), and not precisely one day.

In addition to food and water, the two men brought a host of measuring devices to assess their body temperatures, as well as their waking and sleeping rhythms. This recording area formed the heart of their living space, flanked either side by their beds.

My Rhythm is Not Your Rythem

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 night. These are “morning types,” and make up about 40 percent of the populace. They prefer to wake at or around dawn, are happy to do so, and function optimally at this time of day. Others are “evening types,” and account for approximately 30 percent of the population. They naturally prefer going to bed late and subsequently wake up late the following morning, or even in the afternoon. The remaining 30 percent of people lie somewhere in between morning and evening types, with a slight leaning toward eveningness, like myself.

You may colloquially know these two types of people as “morning larks” and “night owls,” respectively. Unlike morning larks, night owls are frequently incapable of falling asleep early at night, no matter how hard they try. It is only in the early-morning hours that owls can drift off. Having not fallen asleep until late, owls of course strongly dislike waking up early. They are unable to function well at this time, one cause of which is that, despite being “awake,” their brain remains in a more sleep-like state throughout the early morning. This is especially true of a region called the prefrontal cortex, which sits above the eyes, and can be thought of as the head office of the brain. The prefrontal cortex controls high-level thought and logical reasoning, and helps keep our emotions in check. When a night owl is forced to wake up too early, their prefrontal cortex remains in a disabled, “offline” state. Like a cold engine after an early-morning start, it takes a long time before it warms up to operating temperature, and before that will not function efficiently.

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 rather unfairly on two counts. First is the label of 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. Others (usually morning larks) will chastise night owls on the erroneous assumption that such preferences are a choice, and if they were not so slovenly, they could easily wake up early. However, night owls are not owls by choice. They are bound to a delayed schedule by unavoidable DNA hardwiring. It is not their conscious fault, but rather their genetic fate.

humans likely evolved to co-sleep as families or even whole tribes, not alone or as couples. Appreciating this evolutionary context, the benefits of such genetically programmed variation in sleep/wake timing preferences can be understood. The night owls in the group would not be going to sleep until one or two a.m., and not waking until nine or ten a.m. The morning larks, on the other hand, would have retired for the night at nine p.m. and woken at five a.m. Consequently, the group as a whole is only collectively vulnerable (i.e., every person asleep) for just four rather than eight hours, despite everyone still getting the chance for eight hours of sleep. That’s potentially a 50 percent increase in survival fitness. Mother Nature would never pass on a biological trait—here, the useful variability in when individuals within a collective tribe go to sleep and wake up—that could enhance the survival safety and thus fitness of a species by this amount. And so she hasn’t.

Have Rhythm, Won't Travel

The advent of the jet engine was a revolution for the mass transit of human beings around the planet. However, it created an unforeseen biological calamity: jet planes offered the ability to speed through time zones faster than our twenty-four-hour internal clocks could ever keep up with or adjust to. Those jets caused a biological time lag: jet lag. As a result, we feel tired and sleepy during the day in a distant time zone because our internal clock still thinks it is nighttime. It hasn’t yet caught up. If that were not bad enough, at night, we are frequently unable to initiate or maintain sleep because our internal clock now believes it to be daytime.

You may have noticed that it feels harder to acclimate to a new time zone when traveling eastward than when flying westward. There are two reasons for this. First, 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. Second, you will remember that when shut off from any outside world influences, 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. Eastward travel, however, which involves a “day” that is shorter in length for you than twenty-four hours, goes against the grain of your innately long internal rhythm to start with, which is why it is rather harder to do.

West or east, jet lag still places a torturous physiological strain on the brain, and a 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. They were considerably more forgetful than individuals of similar age and background who did not frequently travel through time zones. Other studies of pilots, cabin crew members, and shift workers have reported additionally disquieting consequences, including far higher rates of cancer and type 2 diabetes than the general population—or even carefully controlled match individuals who do not travel as much.

Recall my flight from San Francisco to London. After arriving that day, I had real difficulty getting to sleep and staying asleep that night. In part, this was because melatonin was not being released during my nighttime in London. My melatonin rise was still many hours away, back on California time. But let’s imagine that I was going to use a legitimate compound of melatonin after arriving in London. Here’s how it works: at around seven to eight p.m. London time I would take a melatonin pill, triggering an artificial rise in circulating melatonin that mimics the natural melatonin spike currently occurring in most of the people in London. As a consequence, my brain is fooled into believing it’s nighttime, and with that chemically induced trick comes the signaled timing of the sleep race. It will still be a struggle to generate the event of sleep itself at this irregular time (for me), but the timing signal does significantly increase the likelihood of sleep in this jet-lagged context.

Sleep Pressure and Caffeine

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. Think of adenosine as a chemical barometer that continuously registers the amount of elapsed time since you woke up this morning.

One consequence of increasing adenosine in the brain is an increasing desire to sleep. This is known as sleep pressure, and it is the second force that will determine when you feel sleepy, and thus should go to bed. Using a clever dual-action effect, high concentrations of adenosine simultaneously turn down the “volume” of wake-promoting regions in the brain and turn up the dial on sleep-inducing regions. As a result of that chemical sleep pressure, when adenosine concentrations peak, an irresistible urge for slumber will take hold. It happens to most people after twelve to sixteen hours of being awake.

Levels of circulating caffeine peak approximately thirty minutes after oral administration. What is problematic, though, is the persistence of caffeine in your system. In pharmacology, we use the term “half-life” when discussing a drug’s efficacy. This simply refers to the length of time it takes for the body to remove 50 percent of a drug’s concentration. Caffeine has an average half-life of five to seven hours. Let’s say that you have a cup of coffee after your evening dinner, around 7:30 p.m. This means that by 1:30 a.m., 50 percent of that caffeine may still be active and circulating throughout your brain tissue. In other words, by 1:30 a.m., you’re only halfway to completing the job of cleansing your brain of the caffeine you drank after dinner.

There’s nothing benign about that 50 percent mark, either. Half a shot of caffeine is still plenty powerful, and much more decomposition work lies ahead throughout the night before caffeine disappears. Sleep will not come easily or be smooth throughout the night as your brain continues its battle against the opposing force of caffeine. 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.

Aging also alters the speed of caffeine clearance: the older we are, the longer it takes our brain and body to remove caffeine, and thus the more sensitive we become in later life to caffeine’s sleep-disrupting influence.

To impress upon you the effects of caffeine, I footnote esoteric research conducted in the 1980s by NASA. Their scientists exposed spiders to different drugs and then observed the webs that they constructed.X Those drugs included LSD, speed (amphetamine), marijuana, and caffeine. The results, which speak for themselves, can be observed in figure 3. The researchers noted how strikingly incapable the spiders were in constructing anything resembling a normal or logical web that would be of any functional use when given caffeine, even relative to other potent drugs tested.

Chapter 3 : Defining and Generating Sleep

Chapter 4 : Ape Beds, Dinosaurs, and Napping with Half a Brain : Who sleeps, How do we sleep, and How much?

ONE OF THESE THINGS IS NOT LIKE THE OTHER

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. Total amount of time is one of the most conspicuous differences in how organisms sleep.

If Only Humans Could

We mere humans and a select number of other terrestrial mammals appear to be far less skilled than birds and aquatic mammals, unable as we are to take our medicine of NREM sleep in half-brain measure. Or are we?

Two recently published reports suggest humans have a very mild version of unihemispheric sleep—one that is drawn out for similar reasons. 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.

How Should We Sleep?

When I was a child in the 1980s, I went on vacation to Greece with my family. As we walked the streets of the major metropolitan Greek cities we visited, there were signs hanging in storefront windows that were very different from those I was used to back in England. They stated: open from nine a.m. to one p.m., closed from one to five p.m., open five to nine p.m.

Today, few of those signs remain in windows of shops throughout Greece. Prior to the turn of the millennium, there was increasing pressure to abandon the siesta-like practice in Greece. A team of researchers from Harvard University’s School of Public Health decided to quantify the health consequences of this radical change in more than 23,000 Greek adults, which contained men and women ranging in age from twenty to eighty-three years old. The researchers focused on cardiovascular outcomes, tracking the group across a six-year period as the siesta practice came to an end for many of them.

As with countless Greek tragedies, the end result was heartbreaking, but here in the most serious, literal way. None of the individuals had a history of coronary heart disease or stroke at the start of the study, indicating the absence of cardiovascular ill health. However, those that abandoned regular siestas went on to suffer a 37 percent increased risk of death from heart disease across the six-year period, relative to those who maintained regular daytime naps. The effect was especially strong in workingmen, where the ensuing mortality risk of not napping increased by well over 60 percent.

We are Special

Chapter 5 : Changes in Sleep Across the Life Span

Sleep 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.

Autism, of which there are several forms, is a neurological condition that emerges early in development, usually around two or three years of age. The core symptom of autism is a lack of social interaction. Individuals with autism do not communicate or engage with other people easily, or typically.

Our current understanding of what causes autism is incomplete, but central to the condition appears to be an inappropriate wiring up of the brain during early developmental life, specifically in the formation and number of synapses—that is, abnormal synaptogenesis. Imbalances in synaptic connections are common in autistic individuals: excess amounts of connectivity in some parts of the brain, deficiencies in others.

alcohol can inflict that same selective removal of REM sleep. Alcohol is one of the most powerful suppressors of REM sleep that we know of. We will discuss the reason that alcohol blocks REM-sleep generation, and the consequences of that sleep disruption in adults, in later chapters. For now, however, we’ll focus on the impact of alcohol

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.

Beyond alcohol abstinence during pregnancy, the time window of nursing also warrants mention. 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. Recently we have discovered what alcohol in breast milk does to the sleep of an infant.

Newborns will normally transition straight into REM sleep after a feeding. Many mothers already know this: almost as soon as suckling stops, and sometimes even before, the infant’s eyelids will close, and underneath, the eyes will begin darting left-right, indicating that their baby is now being nourished by REM sleep. A once-common myth was that babies sleep better if the mother has had an alcoholic drink before a feeding—beer was the suggested choice of beverage in this old tale. For those of you who are beer lovers, unfortunately, it is just that—a myth. Several studies have fed infants breast milk containing either a non-alcoholic flavor, such as vanilla, or a controlled amount of alcohol (the equivalent of a mother having a drink or two). 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. Often, the babies will even try to get back some of that missing REM sleep once they have cleared it from their bloodstream, though it is not easy for their fledgling systems to do so.

Sleep and Adolescence

Feinberg’s study reminds me of a billboard advertisement I once saw from a large insurance firm, which read: “Why do most 16-year-olds drive like they’re missing part of their brain? Because they are.”

Chapter 6 : Mother and Shakespeare Knew

Sleep the Night Before Learning

Sleep before learning refreshes our ability to initially make new memories. It does so each and every night. While we are awake, the brain is constantly acquiring and absorbing novel information (intentionally or otherwise). Passing memory opportunities are captured by specific parts of the brain. For fact-based information—or what most of us think of as textbook-type learning, such as memorizing someone’s name, a new phone number, or where you parked your car—a region of the brain called the hippocampus helps apprehend these passing experiences and binds their details together. 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.

We began testing this theory using daytime naps. We recruited a group of healthy young adults and randomly divided them into a nap group and a no-nap group. At noon, all the participants underwent a rigorous session of learning (one hundred face-name pairs) intended to tax the hippocampus, their short-term memory storage site. As expected, both groups performed at comparable levels. Soon after, the nap group took a ninety-minute siesta in the sleep laboratory with electrodes placed on their heads to measure sleep. The no-nap group stayed awake in the laboratory and performed menial activities, such as browsing the Internet or playing board games. Later that day, at six p.m., all participants performed another round of intensive learning where they tried to cram yet another set of new facts into their short-term storage reservoirs (another one hundred face-name pairs). Our question was simple: Does the learning capacity of the human brain decline with continued time awake across the day and, if so, can sleep reverse this saturation effect and thus restore learning ability?

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. The difference between the two groups at six p.m. was not small: a 20 percent learning advantage for those who slept.

Sleep the night After Learning

You will recall from chapter 3 that we obtain most of our deep NREM sleep early in the night, and much of our REM sleep (and lighter NREM sleep) late in the night. After having learned lists of facts, researchers allowed participants the opportunity to sleep only for the first half of the night or only for the second half of the night. In this way, both experimental groups obtained the same total amount of sleep (albeit short), yet the former group’s sleep was rich in deep NREM, and the latter was dominated instead by REM. The stage was set for a battle royal between the two types of sleep. The question: 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 result was clear. It was early-night sleep, rich in deep NREM, that won out in terms of providing superior memory retention savings relative to late-night, REM-rich sleep.

Sleep for Other Types of Memory

There are, however, many other types of memory within the brain, including skill memory. Take riding a bike, for example. As a child, your parents did not give you a textbook called How to Ride a Bike, ask you to study it, and then expect you to immediately begin riding your bike with skilled aplomb. Nobody can tell you how to ride a bike. Well, they can try, but it will do them—and more importantly you—no good. You can only learn how to ride a bike by doing rather than reading. Which is to say by practicing. The same is true for all motor skills, whether you are learning a musical instrument, an athletic sport, a surgical procedure, or how to fly a plane.

your brain will continue to improve skill memories in the absence of any further practice. It is really quite magical. Yet, that delayed, “offline” learning occurs exclusively across a period of sleep, and not across equivalent time periods spent awake, regardless of whether the time awake or time asleep comes first. Practice does not make perfect. It is practice, followed by a night of sleep, that leads to perfection.

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 : Too Extreme for the Guinness Book of World Records

You do not know how Sleep Deprived you are when you are sleep Deprived

The third key finding, common to both of these studies, is the one I personally think is the most harmful of all. When participants were asked about their subjective sense of how impaired they were, they consistently underestimated their degree of performance disability. It was a miserable predictor of how bad their performance actually, objectively was. 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.”

You may find it surprising to learn that vehicle accidents caused by drowsy driving exceed those caused by alcohol and drugs combined. Drowsy driving alone is worse than driving drunk. That may seem like a controversial or irresponsible thing to say, and I do not wish to trivialize the lamentable act of drunk driving by any means. Yet my statement is true for the following simple reason: drunk drivers are often late in braking, and late in making evasive maneuvers. But when you fall asleep, or have a microsleep, you stop reacting altogether. A person who experiences a microsleep or who has fallen asleep at the wheel does not brake at all, nor do they make any attempt to avoid the accident. As a result, car crashes caused by drowsiness tend to be far more deadly than those caused by alcohol or drugs. Said crassly, when you fall asleep at the wheel of your car on a freeway, there is now a one-ton missile traveling at 65 miles per hour, and no one is in control.

Can Naps Help?

When Dinges and Rosekind reported their findings to the FAA, they recommended that “prophylactic naps”—naps taken early during long-haul flights—should be instituted as policy among pilots, as many other aviation authorities around the world now permit. The FAA, while believing the findings, was not convinced by the nomenclature. They believed the term “prophylactic” was ripe for many a snide joke among pilots. Dinges suggested the alternative of “planned napping.” The FAA didn’t like this, either, feeling it to be too “management-like.” Their suggestion was “power napping,” which they believed was more fitting with leadership- or dominance-based job positions, others being CEOs or military executives. And so the “power nap” was born.

The problem, however, is that people, especially those in such positions, came to erroneously believe that a twenty-minute power nap was all you needed to survive and function with perfect, or even acceptable, acumen. Brief power naps have become synonymous with the inaccurate assumption that they allow an individual to forgo sufficient sleep, night after night, especially when combined with the liberal use of caffeine.

Having learned this, I imagine that some readers now believe that they are one of these individuals. That is very, very unlikely. The gene is remarkably rare, with but a soupçon of individuals in the world estimated to carry this anomaly. To impress this fact further, I quote one of my research colleagues, Dr. Thomas Roth at the Henry Ford Hospital in Detroit, who once said, “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.”

Chapter 8 : Cancer, Heart Attacks, and Shorter Life

Sleep Loss and The Reproductive System

If you have hopes of reproductive success, fitness, or prowess, you would do well to get a full night’s sleep every night. Charles Darwin would, I’m sure, cleave easily to this advice, had he reviewed the evidence I now present.

Take a group of lean, healthy young males in their mid-twenties and limit them to five hours of sleep for one week, as a research group did at the University of Chicago. 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. The experimental results support the finding that men suffering from sleep disorders, especially sleep apnea associated with snoring, have significantly lower levels of testosterone than those of similar age and backgrounds but who do not suffer from a sleep condition.

Uttering the results of such studies will often quell any vocal (alpha) males that I occasionally come across when giving public lectures. As you may imagine, their ardent, antisleep stance becomes a little wobbly upon receiving such information. With a genuine lack of malice, I proceed to inform them that 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. I usually conclude my response with a parenthetical low blow, noting that these under-slept men also have significantly smaller testicles than well-rested counterparts.

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.”

Sleep Loss, Genes, and DNA

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.

Chapter 9 : Routinely Psychotic

Chapter 10 : Dreaming as Overnight Therapy

Chapter 11 : Dream Creativity and Dream Control

Chapter 12 : Things That Go Bump in the Night

Somnambulism

SOMNAMBULISM 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.

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).

Narcolepsy

There are at least three core symptoms that make up the disorder: (1) excessive daytime sleepiness, (2) sleep paralysis, and (3) cataplexy.

Chapter 13 : ipads, Factory Whistles, and Nightcaps

Get the Night Time Chills

bedroom temperature of around 65 degrees Fahrenheit (18.3°C) is ideal for the sleep of most people, assuming standard bedding and clothing. This surprises many, as it sounds just a little too cold for comfort. Of course, that specific temperature will vary depending on the individual in question and their unique physiology, gender, and age. But like calorie recommendations, it’s a good target for the average human being. Most of us set ambient house and/or bedroom temperatures higher than are optimal for good sleep and this likely contributes to lower quantity and/or quality of sleep than you are otherwise capable of getting. Lower than 55 degrees Fahrenheit (12.5°C) can be harmful rather than helpful to sleep, unless warm bedding or nightclothes are used. However, most of us fall into the opposite category of setting a controlled bedroom temperature that is too high: 70 or 72 degrees. Sleep clinicians treating insomnia patients will often ask about room temperature, and will advise patients to drop their current thermostat set-point by 3 to 5 degrees from that which they currently use.

Knowingly or not, you have probably used this proven temperature manipulation to help your own sleep. A luxury for many is to draw a hot bath in the evening and soak the body before bedtime. We feel it helps us fall asleep more quickly, which it can, but for the opposite reason most people imagine. 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.

An Alarming Facts

Adding to the harm of evening light and constant temperature, the industrial era inflicted another damaging blow to our sleep: enforced awakening. With the dawn of the industrial age and the emergence of large factories came a challenge: How can you guarantee the en masse arrival of a large workforce all at the same time, such as at the start of a shift?

The solution came in the form of the factory whistle—arguably the earliest (and loudest) version of an alarm clock. The whistle’s skirl across the working village aimed to wrench large numbers of individuals from sleep at the same morning hour day after day. A second whistle would often signal the beginning of the work shift itself. Later, this invasive messenger of wakefulness entered the bedroom in the form of the modern-day alarm clock (and the second whistle was replaced by the banality of time card punching).

Most of us are unaware of an even greater danger that lurks within the alarm clock: the snooze button. If alarming your heart, quite literally, were not bad enough, using the snooze feature means that you will repeatedly inflict that cardiovascular assault again and again within a short span of time. Step and repeat this at least five days a week, and you begin to understand the multiplicative abuse your heart and nervous system will suffer across a life span. 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. This unavoidably means the use of an alarm clock for many individuals. If you do use an alarm clock, do away with the snooze function, and get in the habit of waking up only once to spare your heart the repeated shock.

Chapter 14 : Hurting and Helping Your Sleep

Should you take two of these before bed?

The older sleep medications—termed “sedative hypnotics,” such as diazepam—were blunt instruments. They sedated you rather than assisting you into sleep. Understandably, many people mistake the former for the latter. 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, 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.

Don't take two of these, Instead try these

The obvious methods involve reducing caffeine and alcohol intake, removing screen technology from the bedroom, and having a cool bedroom.

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.

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.

Chapter 15 : Sleep and Society : What Medicine and Education Are Doing Wrong; What Google and NASA Are Doing Right

The Inhumane Use of Sleep Loss in Society

An eloquent yet distressing affirmation of this fact is provided by the former prime minister of Israel, Menachem Begin, in his autobiography, White Nights: The Story of a Prisoner in Russia. In the 1940s, years before taking office in 1977, Begin was captured by the Soviets. He was tortured in prison by the KGB, one component of which involved prolonged sleep deprivation. Of this experience (which most governments benignly describe as the practice of “prisoner sleep management”), he writes:

In the head of the interrogated prisoner a haze begins to form. His spirit is wearied to death, his legs are unsteady, and he has one sole desire: to sleep, to sleep just a little, not to get up, to lie, to rest, to forget . . . Anyone who has experienced this desire knows that not even hunger or thirst are comparable with it . . . I came across prisoners who signed what they were ordered to sign, only to get what their interrogator promised them. He did not promise them their liberty. He promised them—if they signed—uninterrupted sleep.

Sleep and Education

As parents, we therefore have a jaundiced view of the need and importance of sleep in our children, sometimes even chastising or stigmatizing their desire to sleep enough, including their desperate weekend attempts to repay a sleep debt that the school system has saddled them with through no fault of their own. I hope we can change. 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. When sleep is abundant, minds flourish. When it is deficient, they don’t.

Sleep and Healthcare

Tragically, this same neglect has resulted in some of the worst global catastrophes punctuating the human historical record. 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. Thousands died from the long-term effects of radiation in the protracted decades following the event, and tens of thousands more suffered a lifetime of debilitating medical and developmental ill health.

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

Individual Transformation

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.