Why We Sleep by Matthew Walker: what critics and readers say

This review draws on published critic reviews and reader ratings as of October 2026.

The book in brief

Why We Sleep: The New Science of Sleep and Dreams was published on 3 October 2017 by Allen Lane in the UK and Scribner in the US. Its author, Matthew Walker, is a professor of neuroscience at UC Berkeley and director of its Center for Human Sleep Science.

Walker's case is that sleep affects almost every system in the body, that many adults routinely get too little, and that this carries real costs for health, safety and performance. The book reached number one on the Sunday Times bestseller list and number eight on the New York Times list.

What reviewers praised

Kirkus Reviews called it "well-organized, highly accessible", praising how clearly Walker explains the science to general readers. Bill Gates, on his GatesNotes blog, called it "an important and fascinating book" that changed how he thought about years of short nights. Reviewers in specialist journals, including the Physiological Society's Physiology News, found it informative and easy to dip into chapter by chapter.

Readers rate it 4.36 from 239,348 Goodreads ratings (October 2026).

What reviewers criticised

Even supportive reviewers added caveats. Gates said he did not accept every claim, including the strength of the link Walker draws between short sleep and Alzheimer's disease, and felt some findings were presented as more settled than the research shows.

The most detailed criticism came from independent researcher Alexey Guzey, whose essay was first published in November 2019. Among his points:

• The book's claim that "the shorter your sleep, the shorter your life span" does not match meta-analyses he cites, which show a U-shaped pattern with the lowest mortality at around seven hours.
• He found no World Health Organization declaration of a "sleep loss epidemic", which the book refers to.
• He argued that a graph adapted in the book omitted a column that did not fit its argument.

BBC Radio 4's More or Less examined the critique, and Columbia University statistician Andrew Gelman discussed it on his blog. Walker published responses to readers' questions in December 2019. Other sleep researchers, including Jim Horne, have disputed the view that everyone needs at least eight hours. Among readers, the common complaints are an alarmist tone and density.

What the guidance says

Guzey's critique cites the US National Sleep Foundation's recommendation of 7 to 9 hours for adults. The broad message that adults benefit from regular, sufficient sleep is not in dispute; the debate is over specific figures and how strongly some links are stated. Anyone with persistent sleep problems should speak to a doctor.

Who it may suit

• May suit: readers who want an accessible tour of sleep science and are happy to read it alongside its critics.
• May want something else: readers looking for a short, practical sleep routine rather than 368 pages of science.

For general information. This review summarises published opinions; it is not an endorsement or medical advice. Read widely and make up your own mind.