Why We Sleep: Unlocking the Power of Sleep and Dreams by Matthew Walker
My rating: 5 of 5 stars
I first heard of this book from Michael Pollan’s short work on caffeine. There, he calls Why We Sleep (to paraphrase) one of the most disturbing books he had read in a while. This caught my attention. How could a book on sleep be disturbing?
From the first page of this book, I knew why. The author, Matthew Walker, is essentially diagnosing a major health crisis that is going on in front of our drooping, baggy eyes—namely, the crisis of insufficient sleep. According to Walker, virtually everything we do—how we work, how we relax, how we seek entertainment—is disruptive of sleep. And he has plenty of studies to show that, when you do not sleep enough, there are serious consequences.
In addition to the familiar cognitive impairments of bad sleep (inability to focus, lack of energy, wild mood swings), there are the long-term health risks, such as the increased likelihood to develop cancer, heart disease, or diabetes. More unfortunate still, there does not seem to be any way of getting around the familiar recommendation of eight hours of sleep per night. We cannot get by with less, and we cannot make it up on the weekend.
Indeed, the news gets worse and worse. Even moderate amounts of alcohol and caffeine can gravely affect sleep (and marijuana, too—sorry); and sleeping pills may do more harm than good. Our phones, tablets, and computers—even our indoor lights—wreak additional damage by throwing off our natural diurnal rhythms. So this pretty much eliminates all of my nightly plans.
What it comes down to, says Walker, is a cultural disrespect for sleep. I am certainly guilty of this. I have always taken pride in using the opportunity of a plane, train, or bus ride to read a book rather than to nod off, and felt secretly superior to those dozing around me. More generally, sleeping is often equated with laziness. Waking up after midday is a moral failing; taking a nap on the job is a fireable offense; and going to bed early is socially questionable. Further, many people—especially in the business world—take pride in their ability to get by on few hours of sleep. Wakefulness is productiveness. But this prejudice is, Walker contends, based on ignorance of the real value of sleep.
Sleep is a biologically basic process. All mammals, birds, and reptiles, some fish, and even insects have been observed in a sleep-like state. Lack of sleep can not only be harmful, but fatal. Some gruesome rat experiments have shown this, as does the rare disease, Fatal Familial Insomnia, in which the brain becomes incapable of generating sleep—which is inevitably fatal. Sleep is just as basic a need as food. And as you might expect from such a basic need, it is hard-wired into our evolution. Indeed, two distinct types of sleep have evolved, which accomplish different purposes: REM and (creatively named) non-REM.
As you may know, the REM stands for “rapid eye movement,” which is when we experience vivid dreams; and it alone accomplishes many things. In addition to fostering creativity by forging novel links between memories, REM sleep apparently keeps us sane (people experimentally deprived of REM sleep for long enough experience symptoms of psychosis). Non-REM is, perhaps, the more restful sort, when new memories are moved from temporary storage to a more permanent location. The two sleep types thus work together and come at predictable moments in the night: deep non-REM sleep early on, and REM closer to the time we wake up. (Short sleep thus selectively cuts down our REM sleep time.)
Walker explains the science because he wants to drive home the importance of sleep—not a luxury, or an indulgence, but a survival mechanism designed by natural selection. With this basic point in hand, Walker goes on to make several social criticisms, and at times the book almost becomes a polemic.
Take driving, for example. Everybody knows that driving drunk is dangerous and irresponsible. But Walker cites studies showing that drowsy driving is, if anything, even more dangerous. When you are sleep deprived, your brain can drift off into what are called “micro-sleeps,” which last just a couple seconds. This is quite enough time to get into a serious car crash. And this is common. Over the Christmas break, everybody I mentioned this to had a story about falling asleep behind the wheel. It has happened to me, too—a thoroughly alarming experience, which thankfully did not result in a crash. Considering this, I cannot help but agree with Walker this issue is just as deserving of public awareness campaigns as inebriated driving.
Walker is also highly critical of how the medical community treats sleep. For one, most general physicians have little training when it comes to sleep, and so are apt to prescribe sleeping pills to patients with insomnia. Unfortunately, sleeping pills merely sedate the brain without generating natural sleep, and so do not really solve the problem. Another issue is that of doctors’ timetables. From residency on, doctors are often expected to work inhumanly long shifts, even though evidence shows that sleep-deprived doctors are less effective by every measure. Another issue is patient sleep. Although sleep is highly conducive to healing, hospitals often present hostile sleep conditions (loud noise, bright lights, poorly scheduled tests), especially in the ICU, which actively impedes recuperation.
Last but not least, Walker contends that many (though not all!) children diagnosed with mental disorders, like ADHD, may really be suffering from a sleep problem, as insufficient sleep can cause many of the same symptoms (lack of focus, lack of emotional control, etc.). This neatly dovetails with another issue: schools. According to Walker, every person has a natural sleep-schedule, and teenagers tend to have a later one than adults. When teenagers are expected to get to class by eight o’clock or earlier, therefore, we are making it impossible for them to adequately sleep, in the same way most adults would not be able to adapt to a job that began at six in the morning. As a result, many teenagers are chronically under-slept. No wonder that they are so considerate and polite.
This certainly resonates with my experience. Not only did my high school start early, but most of the musical extra-curriculars took place in the hour before regular classes. This meant that I had to arrive by quarter to eight, while I hardly ever went to bed before midnight (often much later). Unsurprisingly, I was a zombie for most of my morning classes. It is easy for me, then, to concur with Walker in proclaiming these early start times for high schools to be illogical and counterproductive. Thankfully this message seems to be slowly sinking in, and some schools have begun pushing back their schedules.
This review, long as it is, hardly does justice to the content of this book. Not only has Matthew Walker written an excellent work of popular science, but he has written a quietly revolutionary work. After all, our society would really look quite different if we took our need to sleep as seriously as we took our need to eat. The world Walkers imagines is certainly a more relaxed and humane one (though, it must be said, perhaps a bit puritanical in its strictures). Imagine, for example, a world when napping during work was encouraged and when start times were flexible. Imagine getting a deduction on your health insurance for sleeping enough. A boy can dream.
There was only one moment in which I doubted the good Walker. In 2015, a study was released that tracked the sleep of three hunter-gatherer groups, and found that they slept, on average, slightly less than seven hours, rather than the expected eight. This seems to undermine Walker’s contention that the modern world is uniquely inimical to sleep. He counters that the study may only show that these hunter-gatherers are also not sleeping enough. But this seems like rather weak tea after telling us of the evils of coffee, alarm clocks, and LED lights. If those free of modern temptations can’t do it right, what hope do we have? Perhaps we are doomed. Even so, I think all of us could benefit by treating our shuteye with a little more respect. Speaking of which, it is already past my bedtime.
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A fellow reviewer on Goodreads, Siddhartha, recommended an article written by the blogger Alexey Guzey that examines the first chapter of Matthew Walker’s book in depth, purporting to find many factual errors. I think it is worth going over Guzey’s points.
First, he notes that, while Walkers claims that longer sleep leads to longer life, in reality studies show a kind of U-curve, where both short and long sleep times are associated with higher mortality. Walker addresses this later on, but defends his position by stating that diseases and comorbidities often lead people to sleep more. Guzey counters that some diseases actually make people sleep less. In any case, Walker’s argument does seem fairly week to me in the absence of evidence that these longer sleep times are certainly caused by diseases. (Also it seems like circular reasoning to assert that anyone sleeping significantly longer than 8 hours must have some sort of disease. Were they presumably under-sleeping before, causing an illness that pushed them into over-sleeping?)
Guzey’s next points out that it is untrue that a good night’s sleep is always beneficial, since sleep deprivation is used as a therapy for depression. Now, to me these seems like nit-picking. One can still say it is almost always beneficial. True, Walker does discount the potential benefits of sleep deprivation therapy without much thought, but that is still a minor point since Walker is not a psychologist.
Guzey’s third point is also somewhat unfair. He points out that it is far from certain that the lack of sleep is what kills victims of Fatal Familial Insomnia. Yes, Walker uses Fatal Familial Insomnia to bolster his claim that lack of sleep is fatal, but he does admit (later on) that it is impossible to say that the lack of sleep is what actually kills in the disease, since victims suffer extensive brain damage. But Walker bases his assertion of the mortality of sleep loss on some (rather cruel) rat studies. Admittedly, we are not rats.
Another of Guzey’s criticisms is that, while Walkers is quite insistent on the eight-hour number, the National Sleep Foundation actually recommends anywhere between seven and nine hours. (And though Walkers invokes the WHO, the World Health Organization has not actually issued sleep recommendations.) This is certainly a legimitate critique of the book, since somebody who sleeps seven hours is actually within the normal range, even though they would get the impression from Walker’s book that they are underslept and at risk.
Several other factual errors Guzey point out are quite valid. It does seem true that, contrary to Walker, the WHO has not declared any sleep loss epidemic in industrialized nations. This is a serious error in itself. Guzey also calls into question whether those in the industrialized world really are getting less sleep now than people did 100 years ago. This claim, in my opinions, does deserves far more scrutiny. True, late night work emails and LED screens are recent inventions. But working on a farm or a factory is hardly more forgiving or flexible. And, again, if hunter-gatherers aren’t sleeping more than we are, perhaps the evidence of a recent sleep loss epidemic is not so strong after all.
Not having done any research myself, I can only give my two cents. I did get the strong impression that Walker consistently emphasized the most potentially dire consequences and examples of sleep loss. And, honestly, I really hope that Walker’s prophecies of doom are somewhat exaggerated, since obtaining perfect sleep while going to work, having a decent social life, keeping up with a hobby or two (not to mention the pressures of raising children—not that I have any) seems close to hopeless.
Even after all of this, I do think that this book is an important corrective to our current cultural disregard of sleep. Thank you for your time.
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