New research reveals that regularly sleeping 7–8 hours could help lower your risk of early death, while irregular or prolonged sleep may signal hidden health risks.
Study: The impact of sleep health on cardiovascular and all-cause mortality in the general population. Image credit: fast-stock/Shutterstock.com
A recent Korean study, published in Scientific Reports, reveals that prolonged sleep duration of more than eight hours is associated with increased mortality risk, particularly in men with regular sleep and women with irregular sleep. The study emphasizes the importance of considering sleep duration and regularity while developing personalized sleep health interventions.
Background
Sleep is an essential physiological process characterized by an altered state of consciousness, reduced physical activity, and reduced responsiveness to external stimuli. Various dimensions of sleep, including duration, quality, regularity, and circadian alignment, collectively contribute to physiological and psychological homeostasis.
Several studies have linked prolonged sleep duration and poor sleep quality with increased risks of cardiovascular and metabolic diseases and all-cause mortality. Emerging evidence has identified sleep regularity (the consistency of sleep–wake timing) as a potentially stronger predictor of cardiometabolic health than sleep duration alone.
Considering the individual impact of different sleep dimensions on human health, researchers from the Hanyang University Medical Center, Republic of Korea, investigated the associations between sleep duration and regularity and risks of major adverse cardiovascular events and all-cause mortality in Korean adults.
Study design
The study included more than 9000 participants from the Korean Genome Epidemiology Study conducted by the Korea Disease Control and Prevention Agency. The participants were rural (Ansung) and urban (Ansan) community residents.
The participants were categorized into multiple groups according to self-reported sleep duration (less than seven hours, seven to eight hours, or more than eight hours) and sleep regularity (regular or irregular).
Appropriate statistical analyses were conducted to investigate the impact of sleep duration, regularity, and their combination on cardiovascular disease and all-cause mortality risks in the study population. Sex-specific analyses were also conducted to assess the potential sex-based differences in these clinical outcomes.
Key findings
The study identified 1,095 deaths and 811 major adverse cardiovascular events in the study population during the follow-up period of over 15 years.
The analysis, adjusting for clinically relevant confounding factors, revealed that participants with more than eight hours of sleep have a significantly higher risk of all-cause mortality than those with seven to eight hours of sleep. A trend toward increased mortality risk was also observed in participants with less than seven hours of sleep, although this did not reach statistical significance.
Regarding sleep regularity, the study found that participants with irregular sleep patterns have a modest but non-significant increase in mortality risk compared to those with regular sleep patterns. However, no significant impact of sleep insufficiency was observed on the all-cause mortality risk. Notably, the study could not find any significant effect of the tested sleep dimensions (sleep duration, regularity, and sufficiency) on the risk of major adverse cardiovascular events after adjustment for confounding factors. However, a non-significant trend was observed in long and irregular sleepers.
The combined analysis of all sleep dimensions revealed that participants with less than seven hours of irregular sleep have the highest mortality risk. Similarly, participants with more than eight hours of regular sleep have a significantly increased mortality risk. In women, more than eight hours of irregular sleep was also linked to higher mortality. A trend toward increased cardiovascular risk was observed in participants with long and irregular sleep.
The sex-specific analysis revealed differential associations of sleep dimensions with mortality risk. In the entire study population, a significantly higher mortality risk was observed in men with less than seven hours of irregular sleep or more than eight hours of regular sleep. In women, however, the highest association for mortality was observed in those with more than eight hours of irregular sleep.
Study significance
The study findings reveal that adults who consistently maintain a particular sleep-wake timing and sleep for seven to eight hours daily are at lower risk of all-cause mortality. Any deviation from this sleep range may increase the risk of mortality. The mortality risk is particularly pronounced among individuals with irregular sleep patterns accompanied by short or long sleep durations, with significant associations observed, especially in men with short irregular or long regular sleep, and women with long irregular sleep.
The study findings highlight the significance of sleep duration and regularity as strong independent predictors of adverse health outcomes. Together with emerging epidemiological and mechanistic findings, these findings suggest that long sleep duration is consistently linked with higher mortality, while short sleep shows a non-significant but concerning trend.
Sleep deprivation is known to increase the risk of various chronic diseases, including hypertension, diabetes, and obesity. The negative influence of short sleep duration on overall health outcomes may help explain the concerning trend towards higher mortality.
A prolonged sleep duration may indicate underlying undiagnosed health conditions or unmanaged comorbidities, such as obstructive sleep apnea, which can potentially increase the risk of cardiovascular events and mortality.
The distinct sex-specific associations observed in the study may be attributed to sex hormone-mediated sleep regulation. In women, hormonal transitions and greater exposure to psychosocial stress and caregiving responsibilities may impact sleep patterns. In men, a higher prevalence of obstructive sleep apnea and work-related stress, such as long working hours, may play a role.
The age-specific associations observed in the study suggest that middle-aged individuals (40 to 49 years) are more likely to develop health adversities due to short sleep duration. On the other hand, older adults (over 60 years) are more susceptible to the adverse effects of prolonged sleep.
Collectively, these findings highlight the need to consider both sleep characteristics and demographic characteristics (age and sex) while developing personalized sleep health interventions for clinical or public health use.
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