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Why We Sleep: An Introduction, Controversy, and Review

By Will Robertson, Associate Editor

Graphic by Madeline Lee

Why We Sleep, written by Matthew Walker, PhD, explores one of science’s foggiest frontiers. A professor of neuroscience and psychology at UC Berkeley, the director of the Center for Human Sleep Science, and a former professor of psychiatry at Harvard University, Walker has had an illustrious career in the scientific field, making his name studying the phenomenon of sleep. Prior to modern research, after all, sleep was impervious to most scientific inquiry. Walker himself highlights the enigmatic nature of sleep at the beginning of his book, pointing out that, up until recently, neither doctors nor scientists could give a complete answer as to why we sleep. Walker lucidly illustrates this ignorance in the first chapter, writing:

To better frame this state of prior scientific ignorance, imagine the birth of your first child. At the hospital, the doctor enters the room and says, “Congratulations, it’s a healthy baby boy. We’ve completed all of the preliminary tests and everything looks good.” She smiles reassuringly and starts walking toward the door. However, before exiting the room she turns around and says, “There is just one thing. From this moment forth, and for the rest of your child’s entire life, he will repeatedly and routinely lapse into a state of apparent coma. It might even resemble death at times. And while his body lies still his mind will often be filled with stunning, bizarre hallucinations. This state will consume one-third of his life and I have absolutely no idea why he’ll do it, or what it is for. Good luck! (5)

Yet, despite its mysterious nature, Walker makes it clear that he considers good sleep more important than exercise or a balanced diet when it comes to maintaining one’s health. Although it is often dismissed as trivial, Walker claims sleep affects nearly every biological function — for better or for worse.

To emphasize the importance of this idea, Walker begins his New York Times bestselling book by listing some claims about the effects of sleep deprivation. On the first page, Walker writes that consistently getting less than six or seven hours of sleep a night demolishes your immune system and more than doubles your risk of cancer. Furthermore, he claims that insufficient sleep is often a key factor in the development of Alzheimer’s disease, unhealthy blood sugar levels, and all manners of cardiovascular disease. Finally, Walker links sleep disruption to mental health, noting that it negatively contributes to “all major psychiatric conditions” (1). In his own words:

Add the above health consequences up, and a proven link becomes easier to accept: the shorter your sleep, the shorter your life span. The old maxim “I’ll sleep when I’m dead” is therefore unfortunate. Adopt this mind-set, and you will be dead sooner and the quality of that (shorter) life will be worse. (4)

However, these flashy claims have not gone unnoticed by the larger scientific community; notably, many statisticians have cried out against the data (or lack thereof) that Walker presents as evidence to his claims. Alexey Guzey, an independent researcher with a background in economics, lambasted Why We Sleep in an essay titled “Matthew Walker’s ‘Why We Sleep’ Is Riddled with Scientific and Factual Errors.” Within, Guzey directly disputes many of the claims fundamental to Walker’s theories and points out claims that seem wholly unsubstantiated. Take Walker’s assertion that chronic sleep deprivation more than doubles your risk of developing cancer; not only does Walker not cite any evidence to back up this galvanizing claim, Guzey references 65 studies that suggest the opposite. Similarly, Columbia University statistician Andrew Gelman attacked an apparent manipulation of data in Why We Sleep, referring to the purported removal of a bar from a graph as a “smoking gun.” In response to these criticisms, Walker has published an online essay on his blog citing much of the previously missing evidence he used while writing the book and explaining potential inaccuracies in his data.

Despite the controversy surrounding the book, I would heartily recommend Why We Sleep to anyone even remotely interested in the study of sleep or a healthy lifestyle. I’m normally averse to non-fiction, so I purchased the book on a leap of faith after reading Bill Gates’s glowing recommendation; although I can’t speak to the scientific correctness of Walker’s more contentious claims, I’ve found the majority of his writing to be incredibly illuminating. With cogent prose, Walker reveals not only the importance of sleep, but also the beauty of the phenomenon itself. By mixing the scientific descriptions of a sleeping brain with the reasons why sleep should matter to us, Walker manages to make the topic of sleep unexpectedly interesting. Now, I simply wonder why so few people seem to take an interest in that miraculous, coma-like state that consumes one-third of our lifespan.

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