Why We Sleep By Matthew Walkerrar Apr 2026

Just one night of four hours of sleep can reduce natural killer (NK) cells —which fight cancer—by up to 70%.

Matthew Walker’s Why We Sleep argues that sleep is a critical biological necessity, not a luxury, influencing every major system in the body and brain. Walker, a professor of neuroscience, emphasizes that routinely getting less than 7–9 hours of sleep leads to severe cognitive impairment and life-threatening health risks. Why We Sleep by Matthew Walkerrar

Occurs primarily in the first half of the night. It serves as a "sensory blackout," during which the brain moves information from short-term to long-term storage and clears out "mental trash". Just one night of four hours of sleep