Association between body roundness index and trajectories of depressive symptoms among Chinese middle-aged and older adults: a nationwide cohort study from CHARLS

Background The relationship between body roundness index (BRI) and longitudinal trajectories of depressive symptoms remains underexplored in middle-aged and older Chinese populations. We therefore aimed to investigate this association utilizing data from a nationally representative longitudinal study. Methods This study utilized longitudinal data from the China Health and Retirement Longitudinal Study (CHARLS) spanning 2011 to 2020. Depressive symptoms were assessed using the validated 10-item Center for Epidemiologic Studies Depression Scale (CESD-10). To capture the heterogeneity in symptom progression, we employed group-based trajectory modeling (GBTM). The association between BRI and depressive symptom trajectories was subsequently examined through multivariable logistic regression analyses, complemented by restricted cubic spline (RCS) regression and stratified analyses to assess potential non-linear relationships and subgroup variations. Results The analysis included 10,335 CHARLS participants with repeated depressive symptom assessments from 2011 to 2020. GBTM identified two distinct trajectories: stable low depressive symptoms (51.80% of participants) and persistent high depressive symptoms (48.20%). After adjusting for potential confounders, multivariable logistic regression revealed an inverse association between BRI and persistent high depressive symptoms (OR = 0.96, 95% CI: 0.93–0.99, P = 0.019). RCS analysis confirmed a linear inverse relationship ( P for non-linearity = 0.116). These inverse associations persisted across stratified analyses with no significant interaction effects between subgroups ( P -interaction > 0.05). Conclusion These findings indicated that elevated BRI values were associated with more favorable depressive symptom trajectories among Chinese middle-aged and older adults.