Forbes December 9, 2025
Most of us treat sleep like it’s a simple budget item: we need to get our eight hours every night and avoid the crash. However, there’s a tiny fraction of the human population who break this rule. Instead, they only sleep four to six hours a night, and they still feel alert and functional. Even more remarkably, they don’t show the cognitive or health deficits normally linked to chronic sleep loss.
Scientists refer to these individuals as familial natural short sleepers (FNSS). And over the last 15 years, geneticists have studied them and found that sleep time is wired in the brain. In turn, they’ve figured out why the “need” for sleep isn’t identical for everyone.
Here’s what geneticists have...
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