Could Sleeping Too Long Be a Health Warning? What a 30-Year Study Found

Sleep is one of the most important parts of maintaining good health. After a busy day, getting into bed and enjoying several uninterrupted hours of rest can feel like exactly what the body needs. But new research suggests that when it comes to sleep, more may not always be better.

A long-term study involving more than 3,000 adults in Taiwan has found an association between sleeping for nine hours or more a night and a higher risk of death from any cause. Interestingly, the study found that the group sleeping seven to eight hours had the lowest mortality rate, while people sleeping fewer than six hours also had a slightly higher rate.

The findings, published in the Journal of Sleep Research in September 2026, are attracting attention because they add to a growing body of research examining the complicated relationship between sleep duration and long-term health. However, the results should not be interpreted as proof that sleeping longer directly causes an earlier death.

What did the researchers discover?

The researchers analysed data from the Chin-Shan Community Cardiovascular Cohort in Taiwan. After exclusions, the study included 3,305 participants who were divided into three groups according to their reported usual sleep duration.

The groups were broadly classified as:

• Short sleep: six hours or less
• Normal sleep: seven to eight hours
• Long sleep: nine hours or more

Participants were followed for a median of approximately 30.8 years, giving researchers an unusually long period in which to examine the relationship between sleep habits and mortality.

According to the study, the seven to eight-hour group recorded the lowest mortality rate. The reported rate was 10.57 deaths per 1,000 people.

For those sleeping fewer than six hours, the rate was slightly higher at 10.97 deaths per 1,000 people. Among participants sleeping more than nine hours, the figure was higher again, at 11.27 deaths per 1,000 people.

The researchers also reported that, after statistical adjustments for potential confounding factors, long sleep was associated with a 17 percent higher risk of all-cause mortality compared with the seven to eight-hour group.

Does nine hours of sleep cause early death?

This is the most important point to understand.

The study found an association. It did not establish that sleeping for nine hours or more directly causes people to die earlier.

There may be other explanations for the relationship. For example, people who regularly sleep for unusually long periods could have underlying health conditions that themselves influence mortality. Long sleep might therefore sometimes be a marker of poorer health rather than the direct cause of it.

The researchers specifically examined whether blood pressure could help explain the relationship. Their analysis suggested that systolic blood pressure may account for part of the association between longer sleep and mortality.

This distinction is particularly important because health and sleep are closely connected. Someone dealing with an illness, fatigue, reduced physical activity or other health problems may spend more time in bed without the additional sleep being responsible for the underlying condition.

Why might longer sleep be linked with health problems?

Scientists do not yet have one definitive explanation.

One possibility is that prolonged sleep could be connected with cardiovascular and metabolic health. The latest study was designed partly to investigate potential biological pathways linking sleep duration with mortality.

Previous research has also reported associations between unusually long sleep and outcomes including cardiovascular disease and all-cause mortality. A 2010 study using data from a Taiwanese community cohort, for example, found an association between longer sleep and all-cause mortality.

Other possible explanations include differences in physical activity, existing medical conditions, sleep quality and other lifestyle factors.

Importantly, sleeping for a long time does not necessarily mean that a person is experiencing poor-quality sleep. Someone may spend nine hours in bed but have fragmented or unrefreshing sleep. The number on the clock therefore tells only part of the story.

What about people who sleep too little?

The findings should not be taken as a reason to cut back on sleep.

In this study, the lowest mortality rate was observed among people sleeping seven to eight hours. The short-sleep group also had a slightly higher mortality rate than the seven to eight-hour group, although the researchers reported that short sleep did not show a statistically significant difference in all-cause mortality after adjustment in their main analysis.

That means there is no evidence from this particular study that deliberately sleeping less is a healthy strategy.

Sleep deprivation has been associated with a range of health and daytime problems, and consistently getting enough sleep remains an important part of healthy living.

Should you worry if you regularly sleep nine hours?

Not necessarily.

Sleep requirements vary between individuals, and one person's normal sleep duration may be different from another's. The latest study does not establish that everyone who sleeps nine hours or more is at increased risk of dying.

Instead, persistent changes in sleep patterns may be worth discussing with a healthcare professional, particularly if long sleep is accompanied by excessive daytime tiredness, loud snoring, breathing interruptions during sleep, difficulty waking, or a noticeable decline in everyday functioning.

The quality of sleep, regularity of the sleep schedule and an individual's overall health are all important considerations.

The bigger lesson about sleep

The study offers a more nuanced message than the dramatic headlines surrounding it might suggest.

Sleep is not simply a case of more being better or less being better. Researchers are increasingly interested in finding a healthy range while also understanding sleep quality, individual differences and the medical conditions that can influence sleeping patterns.

The new research provides evidence that very long sleep is associated with higher all-cause mortality in this particular long-term cohort. It also adds to previous research suggesting that the relationship between sleep duration and health may follow a pattern in which both unusually short and unusually long sleep can be associated with poorer outcomes.

For most people, the practical takeaway is not to panic about occasionally sleeping late. Instead, maintaining a consistent sleep routine and paying attention to persistent changes in sleep may be more useful.

If someone suddenly begins sleeping considerably longer than usual, particularly if they remain tired during the day, that change may deserve attention.

Ultimately, a good night's sleep should be viewed as part of a wider picture of health rather than as a single number of hours.

Sources

• Lin, Y.-C., Chien, K.-L., Lin, H.-J., Su, T.-C., Wang, J., and CARES Study Group (2026). All-Cause and Cardiovascular Mortality in Relation to Sleep Duration: A Community-Based Cohort With Over 30 Years of Follow-Up. Journal of Sleep Research. The study analysed 3,305 participants from Taiwan over a median follow-up of 30.8 years and reported that sleeping nine hours or more was associated with a higher risk of all-cause mortality compared with seven to eight hours.
• Yin, J. et al. (2017). Relationship of Sleep Duration With All-Cause Mortality and Cardiovascular Events: A Systematic Review and Dose-Response Meta-Analysis of Prospective Cohort Studies. Journal of the American Heart Association. This large meta-analysis examined evidence from prospective cohort studies and found an association between longer sleep duration and increased mortality and cardiovascular risk.

Disclaimer: This article is for general information and educational purposes only. It does not constitute medical advice, diagnosis or treatment. The study described here found an association between long sleep duration and mortality, not proof that sleeping longer causes premature death. Individual sleep needs vary. If you have concerns about your sleep, persistent tiredness or a significant change in your sleeping pattern, consult a qualified healthcare professional.