Why We Sleep

What the book is about

Why We Sleep is sleep scientist Matthew Walker’s case that sleep is one of the most important things you do for your health, and one of the most neglected. Drawing on two decades of research, he explains what sleep does for the brain and body, and what goes wrong when we don’t get enough.

It ranges from animal studies to large human studies, covering deep sleep and REM sleep, dreams, caffeine and alcohol, and how our sleep changes from childhood to old age. It also gives practical guidance for sleeping better.

Who wrote it

Matthew Walker is a British neuroscientist, born in Liverpool and raised there and in Chester. He studied neuroscience at the University of Nottingham and was later a professor of psychiatry at Harvard. He is now professor of neuroscience and psychology at UC Berkeley, where he founded and directs the Center for Human Sleep Science. Why We Sleep was his first book, and he now hosts The Matt Walker Podcast on sleep, the brain and the body.

What readers are saying

What they love: Readers say Walker makes dense science easy to follow, with memorable analogies and stories. Many say it changed their habits, from cutting late coffee to treating bedtime as non-negotiable. It topped the Sunday Times bestseller list, made the New York Times list too, and was named a 2017 book of the year by papers including the Guardian, the FT and the Observer.

What they don’t: The book has a serious credibility problem. In 2019, researcher Alexey Guzey published a long critique arguing it is full of errors, overstates the dangers of short sleep and misrepresents research, including a claim that short sleep doubles your cancer risk. With Columbia statistician Andrew Gelman, he also accused Walker of leaving out part of a reproduced graph that contradicted his argument. The row was covered by the BBC’s More or Less. Walker has acknowledged some errors and said a later edition corrected mistakes from the first.

What well-known names said: Bill Gates called it “an important and fascinating book”, though he and other fans have noted that Walker doesn’t always back his claims with solid evidence. The Guardian called it startling and vital, and the Evening Standard described Walker as probably one of the most influential people on the planet.