One gene lets some people sleep just six hours

Researchers at the University of California, San Francisco studied a family in which two members naturally woke up refreshed after only about six hours of sleep a night, looking for a genetic explanation rather than assuming it was simply a habit or a tolerance for tiredness.

Sequencing identified a mutation in a gene called DEC2 shared by the short-sleeping family members but absent in relatives with typical sleep needs. When the team engineered mice to carry the identical human mutation, those mice also slept less than normal mice and needed less catch-up sleep after being kept awake.

DEC2 normally helps regulate the body's sleep-wake cycle, and this particular mutation appeared to change how much sleep the body needs, rather than leaving a hidden sleep debt. The finding came from one extended family, so it explains a rare genetic case rather than suggesting most short sleepers carry this mutation or that sleep need can be safely engineered in everyone else.

A single gene redrew what counted as enough sleep.