Episode 102: Why We Sleep

2026-07-28

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In 2017, Matthew Walker’s Why We Sleep became a huge bestseller. It said, among other things, that we are living through an epidemic of sleeplessness, that the less we sleep the sooner we die, and that sleeping less than six hours a night doubles your risk of cancer.But are its claims as robust as you might hope? Well, you’ve listened to this podcast before, so what do you think?This podcast is sponsored by Works in Progress magazine. Find endless fascinating pieces on human progress at

In 2017, Matthew Walker’s Why We Sleep became a huge bestseller. It said, among other things, that we are living through an epidemic of sleeplessness, that the less we sleep the sooner we die, and that sleeping less than six hours a night doubles your risk of cancer.

But are its claims as robust as you might hope? Well, you’ve listened to this podcast before, so what do you think?

This podcast is sponsored by Works in Progress magazine. Find endless fascinating pieces on human progress at worksinprogress.co.

Show notes

* Matthew Walker’s TED Talk (”Sleep is your superpower”)

* Bill Gates’s glowing GatesNotes review of Why We Sleep

* Alexey Guzey’s 130-hour fact-check of the book’s first chapter — the source for most of this episode

* His appendix of reader emails on the anxiety the book caused

* On “the shorter your sleep, the shorter your life span” — the two mortality meta-analyses Guzey cites: Cappuccio et al. 2010 and the 2016 dose-response one (both U-shaped, optimum ~7 hours)

* On “more than doubling your risk of cancer” — Zhao et al.’s 2018 review in BMC Cancer (65 studies, ~1.55m participants, 86,201 cancers; central OR never above ~1.1)

* On whether the West is sleeping less — the review with the table of nationally representative surveys (the table itself)

* On the Alzheimer’s claim — the paper suggesting reverse causation (early dementia symptoms include sleeplessness)

* The alleged data manipulation:

* Yngve Høiseth’s misconduct complaint to UC Berkeley (the deleted graph bar as “falsification”)

* Andrew Gelman on “institutional failure”

* Scott Alexander’s “If It’s Worth Your Time to Lie, It’s Worth My Time to Correct It”

* The cheese wrap reel

* What we actually know — the 2024 UK Biobank accelerometer study (~60,000 people; sleep regularity more predictive than duration)

* Walker’s 2020 Carl Sagan Prize for Science Popularization — awarded after Guzey’s critique

Credits

The Science Fictions podcast is produced by Julian Mayers at Yada Yada Productions.

This is a public episode. If you'd like to discuss this with other subscribers or get access to bonus episodes, visit sciencefictionspod.substack.com/subscribe

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