The impacts of low back pain and sleep duration on the long-term change in depressive symptoms among middle-aged and older Chinese adults

BACKGROUND: This study aimed to explore the individual and combined effect of low back pain (LBP) and nighttime sleep duration (NSD) on depressive symptoms (DS), as well as to examine whether these associations were modified by daytime napping. METHODS: Data from 5588 participants in the China Health and Retirement Longitudinal Study (2011-2018) were analyzed. Generalized estimating equation models were fitted to explore the individual and combined effects of baseline LBP and NSD on subsequent DS scores. The Cox proportional hazards regression model was employed to assess the combined effect of LBP and NSD on DS. Subgroup analyses were performed to explore whether these associations differed by daytime napping. RESULTS: During a mean follow-up of 5.95 years, 2427 participants developed DS. Simultaneous exposure to LBP and short NSD significantly increased DS scores from visit 2 (β = 3.711, 95 % CI = 3.040-4.383) to visit 4 (β = 5.353, 95 % CI = 4.555-6.151), with the fastest increasing rate. The hazard ratio (HR) with 95 % CI for DS incidence was 2.028 (1.721, 2.390) among participants with LBP and short NSD. Subgroup analyses showed that daytime nappers with LBP and long NSD did not significantly increase the DS scores from visit 2 (β = 1.087, P = 0.390) to visit 4 (β = 2.934, P = 0.126). CONCLUSIONS: LBP and short NSD predict higher DS scores and the risk of DS, while daytime napping may reduce the risk of DS among individuals with LBP and long NSD.