Longitudinal associations between sleep duration and subjective well-being in middle-aged and the older Chinese adults: the mediating role of depressive symptoms

Background Evidence on how sleep duration affects subjective well-being and depressive symptoms in older Chinese adults remains limited. Methods Data from 10,706 participants aged 45 years and above in the China Health and Retirement Longitudinal Study (CHARLS) were analyzed. Descriptive statistics, restricted cubic spline models, and subgroup analyses were conducted. Mediation analysis with 1,000 bootstrap iterations assessed the mediating role of depression. Results Sleep duration was significantly associated with depression, self-rated health, life satisfaction, and life expectancy. Regression models indicated that approximately 6.5 hours of sleep was linked to the lowest depression risk and the highest well-being. Longer sleep was positively related to life satisfaction and self-rated health, though the effect plateaued beyond 6.5 hours. Gender subgroup analysis showed consistent patterns. Mediation analysis revealed that depressive symptoms partially mediated the association between sleep duration and subjective well-being. Conclusion Adequate sleep duration, particularly around 6.5 hours, is linked to lower depression risk and greater subjective well-being in Chinese middle-aged and older adults. Early screening for sleep and mental health issues in high-risk groups may help promote healthy aging.