Sleep loss keeps the "fight-or-flight" system in overdrive, leading to higher blood pressure and increased risks of heart attack and stroke.

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

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".

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

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