Sleep Duration And Risk Of All-Cause Mortality: A Comprehensive Systematic Review Of Observational Evidence

Abstract

Sleep duration is an important determinant of health, yet its association with all-cause mortality remains incompletely understood. This systematic review evaluated the relationship between sleep duration and all-cause mortality in adult populations and examined the influence of age, sex, comorbidities, physical activity, and sleep quality. A comprehensive search of PubMed and BMJ databases was conducted for studies published between January 2000 and April 2025. Observational studies assessing sleep duration in relation to all-cause mortality among adults were included. Data were extracted using a standardized framework, and study quality was appraised using the Hawker et al. tool. Due to methodological heterogeneity, findings were synthesized narratively. Of 52,536 screened records, 33 observational studies met the inclusion criteria. Most studies demonstrated a consistent U- or J-shaped association between sleep duration and mortality. Short sleep duration (<6 hours) was associated with a 10%–40% increased mortality risk, while long sleep duration (>9 hours) showed stronger associations, with hazard ratios ranging from 1.26 to 2.00. Higher risks were observed among older adults, men, and individuals with chronic conditions. Poor sleep quality, prolonged daytime napping, and irregular sleep patterns further increased mortality risk, whereas short naps and adequate physical activity appeared protective. Cognitive impairment amplified the adverse effects of long sleep duration. The lowest mortality risk was consistently observed among individuals sleeping 7–8 hours per night. In conclusion, both short and long sleep durations are independently associated with increased all-cause mortality, highlighting the importance of balanced sleep and lifestyle factors in promoting longevity.