Why We Sleep

I. Introduction

The title of Matthew Walker’s book is misleading, in that it suggests that we sleep for one reason. When in truth, sleep enhances our ability to learn, memorize and make logical decisions. It recalibrates our emotions, replenishes our immune system, fine-tunes our metabolism and regulates our appetite. The answer to why we sleep, then, is because nearly every biological function in the body depends on sleep.

And knowing that our well-being is contingent on regular and sufficient sleep, humans are the only species who regularly deprive themselves of sleep. The result is more than a passing concern, it’s a health crisis. In fact, the World Health Organization has declared sleep loss an epidemic in industrialized nations. Of the four main biological drives — eating, drinking, reproducing and sleeping — sleep, and why humans try to get by without it, is a puzzle that scientists have yet to solve.

Walker, director of UC Berkeley’s Sleep and Neuroimaging Lab, theorizes that people aren’t sleeping enough in part because doctors don’t adequately explain the importance of sleep. Granted, it’s not an easy subject, and our need for sleep is complex. But what’s perfectly clear, according to Walker, is that “sleep is the single most effective thing we can do to reset our brain and body health each day.”

II. The Rhythm of Sleep

III. The Life Cycle: How Sleep Changes

IV. Why Sleep Matters

V. Take Two and Call It Sleep the Morning

VI. Sleep Disorders

VII. A New Vision for Sleep