# Matthew Walker's "Why We Sleep" Is Riddled with Scientific and Factual Errors

This was one of the most thought-provoking posts I read this month. Mostly because I spent a really large number of hours of my life sleeping, and also significantly increased the amount that I've been sleeping over the past three years, and this has me seriously considering reducing that number again. 

The opening section of the article: 

> [Matthew Walker](https://www.sleepdiplomat.com/professor) ([a](https://perma.cc/3BKW-LAQH)) is a professor of neuroscience and psychology at the University of California, Berkeley, where he also leads the Center for Human Sleep Science.
> 
> His book [*Why We Sleep*](https://en.wikipedia.org/wiki/Why_We_Sleep) ([a](https://perma.cc/7GFX-TKUT)) was published in September 2017. Part survey of sleep research, part self-help book, it was praised by [The New York Times](https://www.nytimes.com/2017/10/10/books/review/snooze-michael-mcgirr-sleep-dreams.html) ([a](https://perma.cc/VS9Y-N7KT)), [The Guardian](https://www.theguardian.com/books/2017/sep/21/why-we-sleep-by-matthew-walker-review) ([a](https://perma.cc/3ZXL-GE9Y)), and many others. It was named [one of NPR’s favorite books of 2017](https://apps.npr.org/best-books-2017/). After publishing the book, Walker gave [a TED talk](https://www.youtube.com/watch?v=5MuIMqhT8DM), [a talk at Google](https://www.youtube.com/watch?v=aXflBZXAucQ), and appeared on [Joe Rogan’s](https://www.youtube.com/watch?v=pwaWilO_Pig) and [Peter Attia’s](https://peterattiamd.com/matthewwalker1/) podcasts. A month after the book’s publication, he [became](https://en.wikipedia.org/wiki/Matthew_Walker_(scientist)#Google) ([a](https://perma.cc/5CJV-JMKN#Google)) a sleep scientist at Google.
> 
> On page 8 of the book, Walker writes:
> 
> **\> \[T\]he real evidence** that makes clear all of the dangers that befall individuals and societies when sleep becomes short have not been clearly telegraphed to the public … In response, this book is intended to serve as a **scientifically accurate intervention** addressing this unmet need **\[emphasis in this quote and in all quotes below mine\]**
> 
> In the process of reading the book and encountering some extraordinary claims about sleep, I decided to compare the facts it presented with the scientific literature. I found that the book consistently overstates the problem of lack of sleep, sometimes egregiously so. It misrepresents basic sleep research and contradicts its own sources.
> 
> In one instance, Walker claims that sleeping less than six or seven hours a night doubles one’s risk of cancer – this is not supported by the scientific evidence. In another instance, **Walker seems to have invented a “fact” that the WHO has declared a sleep loss epidemic.** In yet another instance, he falsely claims that the National Sleep Foundation recommends 8 hours of sleep per night, and then uses this “fact” to falsely claim that two-thirds of people in developed nations sleep less than the “the recommended eight hours of nightly sleep” – a myth that spread like wildfire after the book’s publication.
> 
> **Walker’s book has likely wasted thousands of hours of life and worsened the health of people who read it and took its recommendations at face value.**
> 
> Any book of *Why We Sleep’s* length is bound to contain some factual errors. Therefore, to avoid potential concerns about cherry-picking the few inaccuracies scattered throughout, **in this essay, I’m going to highlight the five most egregious scientific and factual errors Walker makes** ***in Chapter 1*** **of the book**. This chapter contains 10 pages and constitutes less than 4% of the book by the total word count.