By Matthew Walker, Scribner, October 3, 2017, 978-1501144325

It’s thorough and well-written. Walker explains the process of sleep in great detail. Then he tells us how we need to change society, particularly school hours. It’s a little bit over the top in the second to last chapter where sleep is the cause of everything.

He presents lots of confirming studies. I am a little skeptical that he doesn’t present some alternative studies that disagree with his bias towards sleep. I found an insignificant factual error (repeating urban legend about coffee trade – see below), which was easily invalidated, but it demonstrates his over the top belief in the studies he presents.

If you don’t know much about sleep, this is very readable book.

[k316] Sadly, 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.

[k319] They are bound to a delayed schedule by unavoidable DNA hardwiring. It is not their conscious fault, but rather their genetic fate. Second is the engrained, un-level playing field of society’s work scheduling, which is strongly biased toward early start times that punish owls and favor larks.

[k320] Second is the engrained, un-level playing field of society’s work scheduling, which is strongly biased toward early start times that punish owls and favor larks.

[k411] 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.

[k413] 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.

[k420] It is the second most traded commodity on the planet, after oil.

NOTE: Not true: In 2017, oil was $788B, aluminum was $106B, copper was $104B, iron ore was $67B, and coffee was $19B.

[k421] continues to this day. Caffeine works by successfully battling with adenosine for the privilege of latching on to adenosine welcome sites–or receptors–in the brain. Once caffeine occupies these receptors,

[k422] Caffeine works by successfully battling with adenosine for the privilege of latching on to adenosine welcome sites–or receptors–in the brain.

[k423] Rather, caffeine blocks and effectively inactivates the receptors, acting as a masking agent.

[k429] Caffeine has an average half-life of five to seven hours.

[k642] This dramatic deceleration of neural time may be the reason we believe our dream life lasts far longer than our alarm clocks otherwise assert.

[k713] 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.

[k825] 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).

[k1034] 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.

[k1081] On average, these tribespeople will fall asleep two to three hours after sunset, around nine p.m. Their nighttime sleep bouts will come to an end just prior to, or soon after, dawn.

NOTE: Do they have night owls and early birds?

[k1090] 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.

[k1127] These napping communities have sometimes been described as “the places where people forget to die.” 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. WE ARE SPECIAL Sleep, as you can now appreciate, is a unifying feature across the animal kingdom, yet within and between species there is remarkable diversity in amount (e.g., time), form (e.g., half-brain, whole-brain), and pattern (monophasic, biphasic, polyphasic).

[k1171] 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.

[k1292] 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.

[k1304] Alcohol is one of the most powerful suppressors of REM sleep that we know of.

[k1417] 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. Taking a closer look at the timing of this relationship, you see something even more interesting. 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. Feinberg made a second seminal discovery. When he examined the timeline of changing deep-sleep intensity at each different electrode spot on the head, it was not the same. Instead, the rise-and-fall pattern of maturation always began at the back of the brain, which performs the functions of visual and spatial perception, and then progressed steadily forward as adolescence progressed.

[k1427] His findings helped explain why rationality is one of the last things to flourish in teenagers, as it is the last brain territory to receive sleep’s maturational treatment.

[k1452] Faulty pruning of brain connections in schizophrenia caused by sleep abnormalities is now one of the most active and exciting areas of investigation in psychiatric illness.

[k1679] Sleep before learning refreshes our ability to initially make new memories .

[k1698] 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.

[k2161] 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.

[k2168] As a result, 1.2 million accidents are caused by sleepiness each year in the United States.

[k2176] As a result, car crashes caused by drowsiness tend to be far more deadly than those caused by alcohol or drugs.

[k2181] 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.

[k2509] Should you experimentally prevent a mouse from getting NREM sleep, keeping it awake instead, there is an immediate increase in amyloid deposits within the brain. Without sleep, an escalation of poisonous Alzheimer’s-related protein accumulated in the brains of the mice, together with several other toxic metabolites.

[k2516] From this cascade comes a prediction: getting too little sleep across the adult life span will significantly raise your risk of developing Alzheimer’s disease. Precisely this relationship has now been reported in numerous epidemiological studies, including those individuals suffering from sleep disorders such as insomnia and sleep apnea.

[k3016] But we had to wait until the advent of brain-imaging machines in the early 2000s before we could reconstruct glorious, three-dimensional visualizations of brain activity during REM sleep. It was worth the wait. Among other breakthroughs, the method and the results undermined the postulates of Sigmund Freud and his nonscientific theory of dreams as wish fulfillment, which had dominated psychiatry and psychology for an entire century. There were important virtues of Freud’s theory, and we will discuss them below. But there were deep and systemic flaws that led to a rejection of the theory by modern-day science.

[k3160] Nevertheless, the psychoanalytic method built on Freudian theory is nonscientific and holds no repeatable, reliable, or systematic power for decoding dreams. This, people must be made aware of.

[k3226] 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.

[k3273] Sleep, and specifically REM sleep, was clearly needed in order for us to heal emotional wounds.

[k3285] 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.

[k3301] The theory proposed that a contributing mechanism underlying the PTSD is the excessively high levels of noradrenaline within the brain that blocks the ability of these patients from entering and maintaining normal REM-sleep dreaming.

[k3321] 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. Raskind had delightfully and inadvertently conducted the experiment I was trying to conceive of myself. He had created precisely the neurochemical condition–a lowering of the abnormally high concentrations of stress-related noradrenaline–within the brain during REM sleep that had been absent for so long in these PTSD patients.

[k3732] While the reasons remain unclear, insomnia is almost twice as common in women than in men, and it is unlikely that a simple unwillingness of men to admit sleep problems explains this very sizable difference between the two sexes. Race and ethnicity also make a significant difference, with African Americans and Hispanic Americans suffering higher rates of insomnia than Caucasian Americans–findings that have important implications for well-recognized health disparities in these communities, such as diabetes, obesity, and cardiovascular disease, which have known links to a lack of sleep. In truth, insomnia is likely to be a more widespread and serious problem than even these sizable numbers suggest.

[k3754] The two most common triggers of chronic insomnia are psychological: (1) emotional concerns, or worry, and (2) emotional distress,

[k3781] Simply put, the insomnia patients could not disengage from a pattern of altering, worrisome, ruminative brain activity.

[k4252] 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. Nightly alcohol will disrupt your sleep, and the annoying advice of abstinence is the best, and most honest, I can offer.

[k4329] Hot baths prior to bed can also induce 10 to 15 percent more deep NREM sleep in healthy adults.

[k4686] 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. They seemed unaware of their poorer work effort and performance–a theme of subjective misperception of ability when sleep-deprived that we have touched upon previously in this book.

[k4898] Teton County in Wyoming enacted an even more dramatic change in school start time, shifting from a 7:35 a.m. bell to a far more biologically reasonable one of 8:55 a.m. The result was astonishing–a 70 percent reduction in traffic accidents in sixteen- to eighteen-year-old drivers.

[k4990] 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.