Why We Sleep

Walker's case for sleep as the foundation of health and cognition made the book a cultural phenomenon and reshaped how many readers think about rest, but it's also become a flashpoint. A widely circulated critique, after roughly 130 hours fact-checking just the first chapter, documented specific claims that don't hold up against Walker's own cited sources, including an unsupported doubling-of-cancer-risk claim and a chart that appeared to omit contradicting data. Walker has defended the book's overall argument and issued corrections in a later edition, and the core case for sleep's importance is not seriously disputed, but readers should know the book's most dramatic statistics have been challenged point by point.