Book

Why We Sleep — Matthew Walker (2017)

Last updated Sat May 30 2026 00:00:00 GMT+0000 (Coordinated Universal Time)

What it covers

The biology of REM and non-REM sleep.
Sleep and memory consolidation.
Sleep and emotional regulation.
Sleep and cardiovascular, metabolic, immune health.
Sleep deprivation's cognitive and mortality costs.
Practical chapters on sleep hygiene and treatment of insomnia.

Strengths

Accessible and engaging style.
Captures the genuine importance of sleep at a level the broader public had under-appreciated.
Practical recommendations are sound.
Influenced wide public adoption of sleep tracking and prioritisation.

What to read critically

The book attracted critique from Alexey Guzey and others for specific overstated effect sizes and contestable individual citations. Walker addressed some critiques but not all. The broader thesis — sleep is central to nearly every aspect of health — remains well-supported by independent literature.

Read it as a strong popular synthesis; verify any specific shocking claim against primary literature if it matters to a decision.

Companion content

Matthew Walker’s lectures on YouTube.
The Matt Walker Podcast (2021–present).
Subsequent academic publications.