Nonlinear association between sleep duration and depressive symptoms among US adults with chronic low back pain: Evidence from NHANES 2009–2010

BackgroundDepressive symptoms are common among individuals with chronic low back pain (CLBP) and are associated with poorer treatment outcomes. Although sleep problems are frequently reported in this population, the dose-response association between sleep duration and depressive symptoms remains unclear.ObjectiveThis study aimed to examine the association between sleep duration and elevated depressive symptoms among U.S. adults with CLBP and to evaluate whether this association showed a nonlinear or threshold pattern.MethodsThis cross-sectional study analyzed adults with CLBP from the 2009-2010 National Health and Nutrition Examination Survey (NHANES). Depressive symptoms were assessed using the Patient Health Questionnaire-9. Survey-weighted multivariable logistic regression and restricted cubic spline analyses were performed.ResultsAmong 568 adults with CLBP, 135 (23.8%) had elevated depressive symptoms. In the fully adjusted survey-weighted model, compared with participants reporting severely insufficient sleep (≤5 h), those sleeping 5-6 h and 7-8 h had significantly lower odds of elevated depressive symptoms, with ORs of 0.31 (95% CI: 0.13-0.76) and 0.51 (95% CI: 0.29-0.88), respectively. Restricted cubic spline analysis showed an L-shaped association, with an inflection point at approximately 6.8 h.ConclusionInsufficient sleep duration was significantly associated with higher depressive symptom burden in individuals with CLBP. Sleep duration may be a clinically relevant marker for identifying depressive symptom burden in this population.