Sleeping 6.4 to 7.8 Hours a Night May Slow Biological Aging

A study published on May 16, 2026 found that sleeping between 6.4 and 7.8 hours per night is associated with slower biological aging. Researchers measured biological age using markers in blood and tissue samples, finding that people who slept outside that range showed signs of faster cellular aging.

The study, reported by Healthline, adds to a growing body of evidence that sleep quality and duration affect long-term health at the molecular level. Biological age, which reflects how quickly the body's cells are aging, can differ significantly from a person's actual age.

People who slept fewer than 6.4 hours showed accelerated aging in the brain and several organs. Those who slept more than 7.8 hours also showed signs of faster aging, though researchers noted that excessive sleep is often a symptom of underlying health conditions rather than a cause of aging.

The findings support existing recommendations from the American Academy of Sleep Medicine, which advises adults to get seven to nine hours of sleep per night. The new research provides a more specific range and links sleep duration directly to biological aging markers.

Experts say the study reinforces the importance of treating sleep as a health priority, not just a lifestyle preference. Poor sleep has already been linked to higher rates of heart disease, diabetes, obesity, and cognitive decline.

"Sleep is when the body repairs itself," said one sleep researcher quoted in the report. "This study shows that the repair process is most effective within a specific window."

The researchers called for more studies to determine whether improving sleep duration can reverse biological aging markers in people who have chronically slept too little.