A long-term study involving over 3,000 participants suggests that sleeping more than nine hours nightly correlates with a higher risk of death. The research, published in the Journal of Sleep Research, identifies seven to eight hours as the optimal duration for longevity.
The 11.27 per 1,000 mortality rate for long sleepers
Data from a three-decade observation period indicates a U-shaped relationship between sleep duration and survival. According to the Journal of Sleep Research, the lowest mortality rate was observed in individuals sleeping seven to eight hours per night, with 10.57 deaths per 1,000 people.. In contrast, those who slept fewer than six hours saw a rate of 10.97 per 1,000.
The most significant risk was found among "long sleepers"—those averaging more than nine hours of sleep. This group experienced the highest mortality rate at 11.27 per 1,000 people. This represents approximately a 17 per cent higher chance of death from any cause compared to the seven-to-eight-hour cohort.
How the Taiwanese research team links sleep to blood pressure
The Taiwanese research team that conducted the study suggests that excessive sleep may be tied to systemic physiological failures. Specifically, the researchers noted that individuals who sleep longer are more prone to high blood pressure, which is a known precursor to stroke and heart disease. However, the team clarified in their paper that blood pressure only accounts for a modest portion of the overall relationship between long sleep and death.
Beyond blood pressure, the Taiwanese researchers pointed to other biological disruptions. They suggest that sleeping too much may trigger higher levels of inflammation or interfere with the body's hormonal balance and immune system.. There is also the possibility that excessive time in bed disrupts the internal biological clock, further compromising overall health.
Beyond mortaltiy: The link to type 2 diabetes and obesity
The findings regarding long sleep duration align with a broader pattern of medical observations. Previous research has already connected excessive sleep to a variety of chronic conditions, including obesity and type 2 diabetes. These comorbidities often overlap with the cardiovascular issues flagged by the Taiwanese team, suggesting that long sleep is rarely an isolated habit but part of a larger health profile.
Furthermore, excessive sleep has been associated with diminished brain health and poorer memory. This creates a complex clinical picture where sleep duration acts as a potential marker for underlying illness. The core question for the medical community remains whether the act of oversleeping causes these declines or if the declines themselves force the body to require more sleep.
Why doctors should track sleep during routine health checks
Because the reasons behind the increased mortality risk are not fully understood, the Taiwanese research team argues that sleep habits should become a standard metric in clinical assessments. They suggest that measuring sleep duration during routine health checks could help physicians identify high-risk adults before severe symptoms manifest.
However, several critical gaps remain in the current data. The study establishes an association rather than a direct cause-and-effect relationship, leaving it unclear if long sleep is a symptom of an undiagnosed condition or a driver of poor health. Additionally, the report does not specify if the quality of sleep—such as interruptions or sleep apnea—influenced the mortality rates of the long-sleeping group.
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