Nonlinear associations between sleep duration and psychological frailty in an aging Chinese population: insights from a national cohort

PURPOSE: To examine the longitudinal and nonlinear association between sleep duration and psychological frailty in middle-aged and older Chinese adults. METHODS: We analyzed 9,476 participants aged ≥45 years in the China Health and Retirement Longitudinal Study. leep duration was reported in 2011, and psychological frailty was assessed using thePsychological Frailty Index in 2018. We examined associations using multivariable logistic regression and restricted cubic splines. Sensitivity analyses incorporated sleep measurements from 2013 and 2015, three-wave average sleep duration, sleep trajectories, and multiple imputation. RESULTS: Short nighttime sleep (<6 h) was associated with higher odds of psychological frailty compared with 6-8 h of sleep (OR = 1.27, 95% CI: 1.08-1.51, p = 0.005). We observed nonlinear associations, with estimated turning points at 7.56 h for nighttime sleep and 8.55 h for total sleep. Persistent short sleep was also associated with higher odds of psychological frailty (OR = 1.44, 95% CI: 1.15-1.81, p = 0.002). Multiple-imputation analyses yielded broadly similar estimates. CONCLUSION: Short nighttime sleep and persistent short sleep were associated with psychological frailty in middle-aged and older Chinese adults. These findings suggest that sleep duration may be relevant to psychological health although causal relationships remain to be established.