A 30-Year Study Found A 17% Higher Mortality Risk With This Sleep Habit
Some nights, nine hours of sleep feels exactly right. Other times, you can spend that long in bed and still wake up exhausted.
If you've started needing more sleep than you used to, it's easy to assume your body simply needs extra rest. But sleep duration can tell us more than how tired we feel.
In a recent study, researchers followed thousands of adults for more than 30 years to examine how their usual sleep duration related to long-term health.
About the study
Researchers analyzed 3,305 adults from the Chin-Shan Community Cardiovascular Cohort, a long-running study in Taiwan. Participants were grouped by their usual sleep duration: six hours or less, seven to eight hours, or nine hours or more.
The researchers then looked at whether sleep duration was associated with mortality from any cause or from cardiovascular disease.
Participants were followed for a median of 30.8 years, allowing researchers to examine how sleep habits earlier in adulthood related to health outcomes decades later.
They also considered factors including age, sex, body mass index, high blood pressure, and diabetes.
The 17% higher risk among long sleepers
After accounting for other health and lifestyle factors, people who regularly slept nine or more hours had a 17% higher risk of mortality from any cause compared with those who slept seven to eight hours.
Importantly, long sleep wasn't significantly associated with cardiovascular mortality specifically.
The researchers also found no meaningful differences in the association based on age, sex, body mass index, high blood pressure, or diabetes.
Sleeping six hours or less wasn't significantly associated with higher mortality risk in this study, either.
Long sleep may be a clue, not the culprit
The finding doesn't mean sleeping nine or more hours causes higher mortality risk, it just shows an association.
One possible explanation came from the researchers' analysis of blood pressure. Systolic blood pressure, the top number in a blood pressure reading, partially explained the relationship between long sleep and mortality.
Other factors could also play a role. Needing more sleep may sometimes reflect an underlying health condition, poor sleep quality, or simply a naturally higher sleep need. The study couldn't determine exactly why the association exists.
How to support your health if you sleep 9+ hours
You don't need to force yourself to sleep less because of this study. Instead, use your sleep pattern as one piece of information about your overall health.
- Pay attention to changes: If you're suddenly sleeping much longer than usual, take note rather than brushing it off. A persistent change is worth discussing with a healthcare professional.
- Check how rested you feel: Nine hours of sleep should generally leave you feeling reasonably restored. If you're regularly exhausted despite getting plenty of sleep, mention it to your doctor.
- Keep an eye on blood pressure: Since blood pressure partially explained the association in this study, knowing your numbers can give you another useful piece of information about your cardiovascular health.
- Keep your sleep schedule consistent: Going to bed and waking up around the same time each day can support a more regular sleep rhythm, rather than focusing solely on hitting a specific number of hours.
- Look beyond your sleep tracker: Sleep duration is only one part of the picture. Your sleep quality, daytime energy, and overall health matter, too.
The takeaway
Longer sleep isn't automatically a sign that something is wrong.
But if your sleep needs have changed or you're still exhausted after a full night, it's worth looking at the bigger picture, including your sleep quality and overall health.