Adults who routinely slept nine or more hours per night had a 17% higher risk of death from any cause than those sleeping seven to eight hours in a Taiwanese cohort followed for more than 30 years.
By yourNEWS Media Newsroom.
Sleeping longer is not always a sign of better health, according to a decades-long study that found adults who regularly reported nine or more hours of sleep per night had a higher risk of dying from any cause than those who typically slept seven to eight hours.
The research followed 3,305 adults in Taiwan for a median of 30.8 years as part of the Chin-Shan Community Cardiovascular Cohort.
Participants were grouped according to their usual sleep duration: six hours or less, seven to eight hours, or nine hours or more.
After researchers adjusted for several health and demographic factors, participants in the longest-sleep group had a 17% higher risk of all-cause mortality compared with those sleeping seven to eight hours.
The findings were reported Sept. 18, 2026, by mindbodygreen.
The results do not establish that sleeping nine or more hours causes an earlier death.
Because the study was observational, researchers could identify an association between long sleep and mortality but could not determine whether longer sleep itself was responsible for the increased risk.
That distinction is particularly important because extended sleep can sometimes reflect another underlying issue.
People with chronic illness, poor-quality sleep, undiagnosed sleep disorders or other medical conditions may spend more time in bed because their sleep is less restorative or because their bodies require additional recovery.
Researchers therefore cautioned that long sleep may function more as a health signal than as the direct cause of poorer outcomes.
Three Decades of Follow-Up
The study drew on the Chin-Shan Community Cardiovascular Cohort, which has tracked adult health in Taiwan over an unusually long period.
Participants’ habitual sleep duration was recorded and compared with mortality outcomes over a median follow-up exceeding three decades.
Researchers adjusted their analysis for factors including age, sex, body mass index, high blood pressure and diabetes.
The relationship between long sleep and mortality did not meaningfully differ according to age, sex, BMI, hypertension or diabetes, according to the report.
That long follow-up period gave investigators an opportunity to examine whether sleep habits measured in adulthood were associated with outcomes many years later.
The strongest result involved all-cause mortality.
Adults reporting nine or more hours of sleep per night had a 17% higher risk of death from any cause than adults in the seven-to-eight-hour group.
The study did not find a statistically significant association between long sleep and cardiovascular mortality specifically.
It also did not find that sleeping six hours or less was significantly associated with higher mortality in this particular cohort.
That latter finding differs from some earlier studies that have associated both unusually short and unusually long sleep with poorer health outcomes.
Blood Pressure May Explain Part of the Association
Researchers found that systolic blood pressure partially accounted for the relationship between longer sleep and mortality.
Systolic pressure is the upper number in a blood pressure reading and represents the pressure in the arteries when the heart contracts.
Elevated systolic pressure is an established cardiovascular risk factor, although the study did not show that blood pressure entirely explained the mortality difference.
The finding raises several possibilities.
Longer sleep could be associated with changes in cardiovascular regulation, or people with underlying health problems that affect blood pressure may also be more likely to sleep longer.
Researchers were unable to determine the exact mechanism.
Other explanations could include poor sleep quality, undiagnosed disease, reduced physical activity, inflammation or simply individual variation in sleep requirements.
The authors therefore did not conclude that reducing time in bed would reduce mortality risk.
Long Sleep May Be a Marker Rather Than a Cause
Previous epidemiological research has often described a U-shaped relationship between sleep and mortality.
Under that pattern, people sleeping at the shortest and longest extremes tend to experience higher mortality rates than people sleeping somewhere in the middle.
Those associations have repeatedly raised the question of whether unusual sleep duration causes health problems or whether existing health problems change how much people sleep.
The Taiwan study adds to that discussion but does not resolve it.
Its finding that short sleep of six hours or less was not significantly associated with increased mortality suggests that sleep-risk relationships may differ among populations.
The study also reinforces the need to distinguish sleep duration from sleep quality.
Someone may spend nine hours in bed but still experience fragmented or poor-quality sleep because of sleep apnea, insomnia or other disturbances.
Another person may naturally sleep nine hours and wake feeling fully restored.
Those two situations are not necessarily equivalent.
Other Sleep Problems Have Been Linked to Poorer Health
Separate research has connected several forms of disturbed sleep with adverse health outcomes.
Chronic insomnia has been associated with increased all-cause mortality in some analyses.
Sleep-disordered breathing, including obstructive sleep apnea, has also been linked with higher risks involving cardiovascular disease and cognitive problems.
Those findings further complicate attempts to interpret sleep duration on its own.
A long night’s sleep may sometimes represent healthy recovery, while in other circumstances it may reflect repeated nighttime awakenings, breathing problems or an underlying condition that leaves someone fatigued despite spending many hours asleep.
Seven to Nine Hours Remains a Common Adult Range
General adult sleep recommendations commonly fall between seven and nine hours per night.
Those recommendations are based in part on an expert review of more than 300 studies published between 2004 and 2014.
That range should not be interpreted as an exact requirement for every adult.
Sleep needs vary with age, genetics, illness, physical activity, pregnancy and other factors.
The latest study therefore does not suggest that someone who naturally sleeps nine hours should intentionally deprive themselves of rest.
Instead, persistent changes in sleep duration may be worth viewing alongside other indicators of health.
A person who suddenly begins needing substantially more sleep, regularly sleeps for long periods but remains exhausted, or develops new daytime sleepiness may benefit from discussing those changes with a healthcare professional.
Monitoring blood pressure may also be useful given the study’s finding that systolic pressure partially explained the association with mortality.
Maintaining a consistent sleep schedule and paying attention to how rested a person feels can provide more useful information than focusing exclusively on a sleep tracker’s nightly number.
As the report put it, “Longer sleep isn’t automatically a sign that something is wrong.”
The larger takeaway is that sleep duration is only one part of the picture.
For most adults, sufficient, regular and restorative sleep remains important for overall health.
The Taiwanese study suggests that consistently sleeping at the long end of the spectrum may sometimes be a marker worth paying attention to, particularly when accompanied by fatigue, health changes or elevated blood pressure.
It does not show that sleeping nine or more hours directly causes earlier death, nor does it provide a reason for otherwise healthy people to intentionally shorten sleep they genuinely need.
Explainer Infographic
Comments