Dynamic Interactions Among Activities of Daily Living, Depressive Symptoms, and Incident Cardiovascular Disease in Chinese Adults Aged 45 and Older: A 7-Year Longitudinal Study

Background Cardiovascular disease (CVD) is a leading cause of morbidity and mortality in older adults. Depressive symptoms and impairments in activities of daily living (ADL) are established CVD risk factors, but their long-term interplay and combined impact on incident CVD remain unclear. This study assessed how cumulative exposure to depressive symptoms, measured by the 10-item Center for Epidemiologic Studies Depression Scale (CES-D), and cumulative ADL impairment jointly influence CVD risk, including mediation pathways, dose–response trends, interaction effects, and potential reverse causality. Methods We analyzed seven-year data (2011–2018) from 4,356 community-dwelling Chinese adults aged ≥ 45 years without baseline CVD in the China Health and Retirement Longitudinal Study. Depressive symptoms (CES-D) and functional status (11-item ADL scale) were assessed at four waves. For each participant, we calculated cumulative average scores for depression and ADL impairment. Incident CVD was identified by self-reported physician diagnosis of heart disease or stroke. Multivariable Cox proportional hazards models estimated hazard ratios (HRs) per one-point increase in cumulative CES-D or ADL score. We conducted causal mediation analyses, tested interaction effects, fitted restricted cubic splines for dose–response, and used cross-lagged panel models to examine reverse causality. Results Among 4,356 participants, 675 (15.5%) developed incident CVD over follow-up. Each one-point increase in cumulative CES-D score conferred a 4% higher CVD risk (HR 1.04, 95% CI 1.02–1.06), and each one-point increase in cumulative ADL score a 14% higher risk (HR 1.14, 95% CI 1.08–1.21). ADL impairment mediated 26.1% of the depression–CVD link, while depressive symptoms mediated 37.9% of the ADL–CVD link. Their joint effect was sub-additive, indicating a ceiling interaction. Dose–response analyses showed positive, partly nonlinear associations. Cross-lagged models provided little evidence of reverse causality. Conclusions In Chinese adults aged ≥ 45 years, long-term depressive symptoms and ADL impairment each independently predict incident CVD, mediate one another’s effects, and interact sub-additively. Early, integrated interventions targeting both mental health and functional ability may be most effective for CVD prevention in aging populations.