Association between functional dependence and cardiovascular disease among middle-aged and older adults: Findings from the China health and retirement longitudinal study

Background: The effect of different functional dependency types on cardiovascular disease (CVD) is largely unknown. Here, we aimed to investigate the association between functional dependence and CVD among middle-aged and older adults by conducting a cross-sectional and longitudinal study. Methods: The study sample comprised 16,459 individuals of >= 40 years (including 10,438 without CVD) who had participated in the 2011 China Health and Retirement Longitudinal Study (CHARLS). Functional dependence was categorized based on the "interval-of-need" method, while CVD was defined as physician-diagnosed heart disease or stroke. Cox proportional hazard regression was employed to assess the effects of functional dependence on CVD. Moreover, patients were grouped according to the functional status changes, and the impact of these changes on CVD was observed. Heterogeneity, subgroup, and interaction analyses were used to evaluate the consistency of the study findings. Finally, a mediation analysis was performed to estimate the potential mediation effects on the relationship between functional dependence and CVD risk. Results: CVD prevalence in the overall study population was 13.73 % (2260/16,459), while its prevalence among individuals with functional independence, low dependency, medium dependency, and high dependency was 9.60 % (1085/11,302), 14.25 % (119/835), 17.72 % (115/ 649), and 25.01 % (941/3763), respectively. Additionally, medium (odds ratio: 1.33, 95 % confidence interval: 1.06-1.68) and high functional dependency (1.55, 95 % CI: 1.38-1.75) were associated with CVD. A total of 2987 (28.62 %) participants with CVD were identified during the 9-year follow-up, with 4.85 % (145/2987) of the CVD cases being attributed to functional dependence. The individuals with medium (HR: 1.20, 95 % CI: 1.01-1.44) and high functional dependency (1.25, 95 % CI: 1.14-1.37) were more likely to develop CVD than their peers with functional independence. Furthermore, persistent functional dependence (HR: 1.72, 95 % CI: 1.52-1.94) and transition from functional independence to dependence (1.79, 95 % CI: 1.61-1.98) were associated with a higher CVD risk than continuous functional independence. Hypertension and diabetes may partially mediate CVD caused by functional dependence. Conclusion: Functional dependence is associated with high CVD risk. Therefore, appropriate healthcare attention must be directed towards functionally dependent populations to protect their cardiovascular health.