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%.

Occurs more frequently in the second half of the night. This stage is essential for "emotional first aid," helping to process traumatic events and foster creative problem-solving by making novel neural connections. Critical Health Impacts of Sleep Deprivation Why We Sleep by Matthew Walkerrar

Short sleep makes fat cells less responsive to insulin, which can lead to pre-diabetic blood sugar levels within just one week of moderate deprivation. Just one night of four hours of sleep

Driving while sleep-deprived can be as dangerous as driving drunk; being awake for 22 hours results in the same level of cognitive impairment as legal intoxication. Practical Tips for Better Sleep Critical Health Impacts of Sleep Deprivation Short sleep

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.

Walker highlights that missing even a small amount of sleep can have "dire" consequences:

Sleep is not a uniform state but a complex cycle of two main stages that serve distinct functions: