Most people need about eight hours of sleep each night to stay alert and healthy. However, a small group can function normally on three to six hours, and researchers may now understand why.
A new study published in the Proceedings of the National Academy of Sciences has identified a rare genetic mutation that could explain how some people naturally need less sleep without facing negative health effects.
Ying-Hui Fu, a sleep researcher at the University of California, San Francisco, began studying short sleepers in the early 2000s when a mother and daughter reached out to her lab. Both reported feeling fully rested despite sleeping fewer than six hours a night.
Fu’s team discovered a rare mutation in a gene linked to the body’s internal clock, which controls sleep and wake cycles. That finding drew attention from others with similar sleep habits, leading to years of research and DNA testing.
Her team has since studied hundreds of naturally short sleepers and found five different mutations across four genes. The exact mutation tends to vary between families, suggesting multiple possible genetic paths to this unusual trait.
In the newest study, Fu and her colleagues discovered another mutation in a gene called SIK3. This gene helps produce an enzyme that supports communication between brain cells.
To understand the mutation’s effects, the team genetically modified mice to carry it. These mice slept about 31 minutes less per day than regular mice, who sleep around 12 hours.
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For true short sleepers… yes.
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Researchers found that the altered enzyme was especially active in brain synapses—the junctions where nerve cells pass signals. This could mean that the mutation helps the brain maintain its balance more efficiently, possibly reducing the need for extended sleep.
Clifford Saper, a neurologist at Harvard Medical School, said the findings align with earlier studies involving the same gene. “This work fits very well with what is known about Sik3,” he said. It “may help us understand the basis for sleepiness.”
While the gene mutation led to only a modest drop in sleep time in mice, researchers say every discovery helps build a clearer picture of sleep.
Fu hopes that identifying more gene changes in natural short sleepers will eventually lead to better treatments for sleep disorders and a deeper understanding of how the human body regulates rest.
