Sleeping just four hours without health issues, a rare genetic trait in 1%

Some individuals claim to sleep only four or five hours and feel fully energized. While this sparks envy, science has long warned that sleep deprivation harms health. Yet, there is a remarkable exception to this rule.

For decades, recommendations from the World Health Organization and sleep experts have been clear: adults need between 7 and 9 hours of sleep to keep their immune system, metabolism, and mental health in check. Sleeping less increases risks of diseases like Alzheimer’s.

However, about 1% of the global population has a genetic superpower that allows them to bypass this norm without negative effects. Researcher Ying‑Hui Fu discovered that these individuals carry a mutation in the DEC2 gene, also known as BHLHE41, which influences sleep regulation.

To reach this conclusion, Fu studied families where some members functioned perfectly on just six hours of sleep, showing no daytime sleepiness or cognitive decline, while others needed more than eight hours. The mutation in DEC2 was the key factor.

Further studies in animals and human families have identified mutations in other genes that seem to optimize sleep, making four hours enough and even providing protection against cognitive decline. Still, these mutations are extremely rare and specific.

It's crucial not to try to replicate these traits. Most people who sleep less by choice face risks like dementia, diabetes, or hypertension if they maintain such patterns long-term. Science warns that chronic sleep deprivation can be very damaging.

Therefore, although sleeping less might seem appealing, only a tiny fraction of the population has this genetic ability. For the rest, sleeping 7 to 9 hours remains the best way to stay healthy and well.