Latent multimorbidity patterns and their longitudinal associations with depressive symptom trajectories and ADL limitations among middle-aged and older adults in China: a longitudinal analysis of the CHARLS

Background Multimorbidity is heterogeneous, but longitudinal evidence from China on how specific disease patterns relate to changes in depressive symptoms and functional limitations remains limited. This study aimed to identify baseline multimorbidity patterns and examine their longitudinal associations with trajectories of depressive symptoms and activities of daily living (ADL) limitations in a nationally representative cohort. Methods Data were drawn from the China Health and Retirement Longitudinal Study (CHARLS), 2011–2018. Latent class analysis (LCA) was used to identify baseline (2011) multimorbidity patterns based on 12 chronic conditions. Linear and generalized linear mixed-effects models were applied to assess the associations between baseline patterns and changes in depressive symptoms and the risk of ADL limitation from 2013 to 2018. Exploratory mediation analysis examined whether pain statistically mediated the association between multimorbidity patterns and subsequent depressive symptoms. Results Four multimorbidity patterns were identified: cardiometabolic (Class 1), respiratory-dominant (Class 2), musculoskeletal–digestive (Class 3), and relatively healthy (Class 4). Compared with Class 4, Class 3 showed a steeper increase in depressive symptom scores over time (β = 0.099, P = 0.020). Findings were directionally consistent in sensitivity analyses, including the random-slope model (β = 0.096) and the high-classification-certainty subsample (β = 0.102). In exploratory mediation analyses, pain indicators measured in 2013 were associated with higher subsequent depressive scores, but no clear statistically indirect effect was observed for Class 3. The risk of ADL limitation increased over time (P < 0.001), but no significant differences in the rate of change were found across patterns (all class-by-time interaction terms P > 0.05). Conclusions Distinct multimorbidity patterns were differentially associated with depressive symptom trajectories among middle-aged and older adults in China. The musculoskeletal–digestive pattern was associated with a faster increase in depressive symptoms over time. Pain may reflect an important symptom-burden correlate of this pattern, but no clear mediation evidence was observed under the current model specification. These findings suggest that mental health screening and symptom-oriented assessment may be particularly relevant for high-symptom-burden multimorbidity patterns in primary care.