The Promise of Sleep

William C. Dement MD makes the case that sleep is a biological requirement on a par with food and activity, that society systematically disregards it, and that the cost appears as accidents, illness and undiagnosed disease. Published in 1999, it is one of the first books to put that argument to a general audience, and much of what followed in the popular sleep literature descends from it.

The book works on two levels. The first is physiological: sleep architecture, the cycling between non-REM and REM stages across the night, and the concept of sleep debt — the idea that lost sleep accumulates and must eventually be repaid rather than simply disappearing. The second is clinical. Dement describes sleep disorders as diagnosable, treatable medical conditions rather than character flaws or complaints to be tolerated, covering obstructive sleep apnoea, narcolepsy, restless legs and circadian rhythm disorders, and arguing that excessive daytime sleepiness is a large and unrecognised contributor to road and workplace accidents.

It is for readers interested in how sleep medicine came into existence as a discipline, and for anyone trying to work out whether their own symptoms point to a disorder worth investigating.

On the evidence: the book is foundational, and its central contention that apnoea and narcolepsy were badly underdiagnosed was correct and remains partly true. It is also more than two decades old. Much of what is now known about sleep and cardiometabolic risk, about clearance of metabolic waste from the brain during sleep, and about cognitive behavioural therapy for insomnia as the first-line treatment for chronic insomnia, arrived after publication. The sleep debt metaphor is a simplification — recovery is not a simple ledger — and confident attributions of specific public disasters to sleepiness are harder to establish than the book implies. Read it as origin story, paired with something current for practice.