Trajectories of depressive symptoms and chronic disease multimorbidity among middle-aged and older Chinese adults: A group-based trajectory modeling study

Abstract Background The co-occurrence of depressive symptoms and chronic diseases among middle-aged and older adults is increasingly prevalent, yet their longitudinal co-developmental patterns have rarely been examined jointly. Objective To identify distinct depressive symptom trajectories among middle-aged and older Chinese adults and examine prevalence patterns of chronic disease comorbidity and associated factors across trajectory groups. Method Using four waves of China Health and Retirement Longitudinal Study (CHARLS) data (2011–2018), 6,636 participants aged ≥ 45 years at baseline who completed at least two follow-up assessments were included. Group-based trajectory modeling (GBTM) was applied to CES-D10 scores. Optimal model selection was based on BIC values, average posterior probabilities, minimum group proportions, and clinical interpretability. Multivariable logistic regression identified factors associated with trajectory group membership. Result Three stable trajectories were identified: low-depressive-symptom (41.88%, n = 2,778), moderate-depressive-symptom (47.68%, n = 3,191), and high-depressive-symptom (10.44%, n = 667) groups, all exhibiting stable trajectories over the 7-year follow-up period. Prevalence rates of all 14 chronic diseases showed a monotonically increasing gradient from the low to high group (all P < 0.05, except Parkinson's disease), with arthritis (from 22.4% to 55.5%), lung disease (from 2.6% to 10.0%), and osteoporosis (from 2.8% to 10.2%) demonstrating the steepest prevalence gradients. Female sex, older age, lower education, and unmarried status all increased progressively with trajectory severity. Conclusion Depressive symptom trajectories in Chinese middle-aged and older adults are heterogeneous but stable. Chronic disease comorbidity burden shows a full-spectrum gradient association with depression severity. Integrated physical–mental screening and care should be prioritized for individuals with chronic pain, respiratory disease, and multiple comorbidities.