Health & wellbeing

Why We Sleep

Matthew Walker

Unlocking the power of sleep and dreams: a neuroscientist argues that sleep supports memory, mood and health, and that modern life gives it too little room

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  • 11 key ideas
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  • Published 2017

Introduction

Matthew Walker, a neuroscientist who studies sleep at the University of California, Berkeley, argues that sleep is not idle time but one of the most important things we do for our brains and bodies. It is his first book, written for general readers and published in 2017.

The book has four parts. "This Thing Called Sleep" explains what sleep is: the body clock, caffeine, the two kinds of sleep and how sleep changes through life. "Why Should You Sleep?" sets out what sleep does for the brain and the body, and what goes wrong when it is cut short. "How and Why We Dream" covers dreaming sleep and its part in emotions and creativity. "From Sleeping Pills to Society Transformed" turns to what gets in the way of sleep, to pills and therapy, and to the changes Walker wants in schools, workplaces and hospitals.

Notes: this summary states the book's claims as Walker makes them. Since 2019 some of them have been disputed by other sleep researchers and writers, among them the independent researcher Alexey Guzey, who published a long critique listing errors and overstatements. For example, the book says the World Health Organization declared a sleep loss epidemic; no such WHO declaration has been found, and Walker later said the claim should have been credited to the US Centers for Disease Control. His strong wording that shorter sleep means a shorter life, and the suggestion that hardly anyone can do well on less than seven or eight hours, go further than some researchers think the evidence allows, and some figures and graphs have also been challenged. Walker has responded to some of the criticism on his website. Read the book as one scientist's argument, not as settled fact. It is not medical advice: if you have trouble sleeping, talk to a doctor.

  1. 1Walker argues that sleep does not have one purpose: it serves the brain and the body in many ways at once
  2. 2Two forces decide when you feel sleepy: an inner body clock, and a chemical pressure that builds up while you are awake
  3. 3Sleep is not one state but two, which alternate through the night: deep sleep without dreams early on, dreaming sleep later
  4. 4Walker argues that sleep prepares the brain to learn, and then locks in what you learned
  5. 5In Walker's account, too little sleep dulls attention, pushes emotions to extremes and may raise the risk of dementia
  6. 6Walker argues that short sleep strains the heart, blood sugar, appetite and defenses against infection
  7. 7Walker proposes that dreaming sleep works as overnight therapy, keeping painful memories but softening their sting
  8. 8In Walker's view, dreaming sleep links distant ideas, which is why it helps with creativity and problem solving
  9. 9Walker argues that bright evening light, alcohol and warm bedrooms quietly undermine sleep
  10. 10Walker argues that sleeping pills sedate rather than give natural sleep, and that therapy should come first for long-term insomnia
  11. 11Walker argues that society treats sleeplessness as a badge of honor, and that schools, workplaces and hospitals should change

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