Why do some people need less sleep than others?

Sleep needs vary due to a combination of genetic, age-related, and lifestyle factors. Some people carry genetic variants, particularly in genes like DEC2 and ADRB1, that allow them to function well on fewer hours of sleep without the cognitive impairment most people would experience. These true "short sleepers" are relatively rare. Beyond genetics, age plays a role, as older adults often sleep less deeply and for shorter durations. Fitness level, stress, diet, and overall health also influence how restorative sleep is, meaning some people achieve the same recovery in less time. Caffeine tolerance and circadian rhythm differences further contribute. It's worth noting that many people who think they need little sleep are actually chronically sleep-deprived and have simply adapted to feeling that way.