My review of Why We Sleep

2020-12-10 1106 words books,

Another book that I’ve read over the past couple of weeks was Matthew Walker’s Why We Sleep. Walker distilled perhaps the most complex biological phenomenon into an accessible 300 pages, and he taught me a lot about this essential process. (Update: maybe not!)

Update: retracting my recommendation

It turns out that this book has a lot of problems! Starting with Alexey Guzey’s blog post about the book being “riddled with scientific and factual errors,” and subsequent analysis by Andrew Gelman, it turns out that:

a lot of claims in the book are exaggerated, misrepresented, or outright false
the author cites this book in academic research, suggesting that it’s supposed to be held to academic standards
the hasn’t responded to any criticism of the book, either!

In the first chapter of Why We Sleep, Walker:

completely misrepresents the relationship between sleep and longevity and between sleep and cancer (Section 1)

erroneously states that getting a good night’s sleep is always beneficial (Section 2)

erroneously states that patients with fatal familial insomnia die because of lack of sleep (Section 3)

seems to invent a “fact” that the WHO has declared a “sleep loss epidemic” (Section 4)

misrepresents National Sleep Foundation’s sleep recommendations and uses them to misrepresent the number of adults failing to get the recommended hours of sleep (Section 5)

also seems to invent the WHO’s sleep recommendations

calls his book “a scientifically accurate intervention”

Given the density of scientific and factual errors and an apparent invention of new “facts” by Walker, I would caution readers against taking the book’s recommendations at face value.

Some supporting links here:

I’m not in a position to evaluate the accuracy of the book, which is why I took the claims at face value! Guzey’s blog post is very convincing, and I must retract my recommendation here!

The previous post

(Update: I wrote this post a month ago and never put it up! Whoops!)

Why did I choose this book? I’ve been fascinated with sleep for a long time. I loved my naps in college and would regularly be found sleeping in common areas. I briefly thought I’d study neuroscience to learn more about the biology behind sleep. And so when I saw Walker’s book recommended online, I picked it up from the library.

On the power of sleep

It should come as no surprise that proper sleep is important to living a healthy life. I knew this, and I think most people do. But I was still taken aback by Walker’s enumeration of the seemingly infinite ways that sleep improves our body and our mind.

Some of the physical benefits:

Sleep improves muscle growth and recovery, cardiovascular health, and metabolic regulation
Sleeping for 7 to 9 hours after receiving a vaccine improves its effectiveness relative to sleeping for less time
When running a calorie deficit (trying to lose weight), sleep deprivation means that more weight loss will come from muscle, not fat
In athletes, a lack of sleep increases injury risk; lowers jump height; reduces peak muscle strength; and limits cardiovascular and respiratory capabilities

56 million Americans admit to struggling to stay awake at the wheel of a car each month. As a result, 1.2 million accidents are caused by sleepiness each year in the United States.

Mentally, meanwhile, a full night of sleep contributes to short- and long-term memory, better association of thoughts, and more creativity. Losing sleep makes it harder to regulate emotions and makes one more likely to develop mental illnesses.

At one point, Walker puts it this way:

Scientists have discovered a revolutionary new treatment that makes you live longer. It enhances your memory and makes you more creative. It makes you look more attractive. … It wards off colds and the flu. It lowers your risk of heart attacks and stroke, not to mention diabetes. You’ll even feel happier, less depressed, and less anxious.

Hyperbolic? You’d think so, but this treatment is consistently sleeping for (roughly) 8 hours a night. It sure sounds magical when you put it that way!

Observations backed by science

One of the main reasons I liked this book is because it revealed the science behind things that I’ve noticed about my own sleep, but never been able to explain. And it did this clearly and accessibly, too!

For example: I regularly get sleepy around 1 – 2 PM. In college, 1PM classes were always the hardest for me to stay focused. These days, around 2PM is when I hit a wall at work, productivity-wise. Some of my friends felt the same way, but I never really knew why.

Walker explains that this is because humans are naturally biphasic:

All humans, irrespective of culture or geographical location, have a hardwired dip in alertness that occurs in the midafternoon hours, … called the post-prandial alertness dip. This brief descent from high-degree wakefulness to low-level alertness reflects an innate drive to be napping and asleep in the afternoon, and not working. It appears to be a normal part of the daily rhythm of life.

Another “oh, that’s how that works!” moment was on nighttime showers. I’ve recently found that showering in the evenings helps me sleep better. It turns out that physiological reason is that the water moves blood to the skin, cooling down my core temperature to aid in sleep.

My recommendation

I don’t think it’s an understatement to say that this book drastically changed my understanding of sleep. I came away with a far more well-rounded perspective on why sleep is so important. It’s too early to say how this will change my own sleeping habits, but I’m more motivated to improve them after reading this.

Walker’s writing is accessible to someone without a biology background, and that’s not easy to do! He manages to go into enough detail to make this feel more fulfilling than a pop science article, but without being as intimidating as a research paper.

There’s so much more packed into this book, too. I didn’t discuss the chapters on the different phases of sleep and on dreaming, but I learned a great deal from those. Walker struck the perfect balance between “here’s what we know” and “here’s what we don’t,” keeping me interested throughout.

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