Sleep Duration and Depression as Predictors of Cancer Incidence in Middle-aged and Older Adults: A Longitudinal Analysis from the China Health and Retirement Longitudinal Study (CHARLS)

Background/Aim: The present study aimed to investigate the association between sleep duration and the risk of newly-onset cancer among middle-aged and elderly adults, and to examine the effect of depression on this association. Patients and Methods: The data from 9,400 participants in the China Health and Retirement Longitudinal Study (CHARLS, 2011-2020) were analyzed. Cox proportional hazards regression models, Kaplan-Meier survival curves, restricted cubic spline (RCS) regression, and threshold-effect analysis were employed to evaluate the relationship between sleep duration and cancer risk. Furthermore, subgroup analyses were conducted to explore potential heterogeneity across populations. Results: Over a median follow-up period of 9.0 years, 271 participants (2.9%) developed newly-onset cancer. Longer sleep duration was associated with a reduced risk of incident cancer [fully adjusted hazard ratio (HR)=0.65, 95% confidence interval (CI)=0.51-0.84]. RCS regression indicated a nonlinear association between sleep duration and the risk of cancer incidence (nonlinearity p=0.005), with an inflection point at 5.0 h of sleep per night. Specifically, sleeping ≥5 h per day was associated with an 18% lower risk of cancer (HR=0.82, 95% CI=0.74-0.91), whereas shorter sleep duration (<5 h) showed no significant protective effect. This protective effect of sleep was more pronounced among individuals with depression (HR=0.64, 95% CI=0.44-0.92). Subgroup analyses further revealed that the protective effect of sleep was stronger among men, urban residents, individuals without hypertension, and smokers. Conclusion: Longer sleep duration (≥5 h) is independently associated with a lower risk of newly-onset cancer in middle-aged and elderly adults, particularly in those with depression. These findings highlight the importance of sleep health for cancer prevention.