Study Links Nine Hours of Sleep With Early Death

Two large bodies of research connect habitual sleep length with mortality, but neither shows that longer sleep causes an earlier death. A Taiwanese investigation tracked more than 3,000 people across 30 years. Compared with participants averaging seven to eight hours, those who routinely exceeded nine hours had a 17% higher association with death from any cause. Persistent long sleep may instead signal an existing health issue or another factor affecting well-being.

The Journal of Sleep Research findings put the difference in perspective. The mortality rate was 10.57 per 1,000 among people getting seven to eight hours, 10.97 per 1,000 among those sleeping under six hours, and 11.27 per 1,000 for people exceeding nine hours regularly. Blood pressure accounted for only a small share of the relationship. Researchers also considered inflammation, disrupted circadian rhythms, and hormonal regulation, though no explanation was established.

A broader analysis from a Semmelweis University team in Budapest combined 79 international publications covering more than 2.1 million people. Built in 2025, it associated fewer than seven hours with a 14% increase in all-cause mortality relative to seven-to-eight-hour sleepers. Nine hours or longer was associated with a 34% increase. The analysis also linked eight or more hours among men with a 36% increase, while habitual long sleep among women was associated with a 44% increase. Both research groups suggest that regular sleep duration could become useful information in routine health check-ups, particularly when extended sleep occurs with continuing fatigue or other health changes.