The joint effect between body mass index and waist circumference in the risk of heart disease: A national longitudinal cohort study

Background: The association between body mass index (BMI), waist circumference (WC), and heart disease is a pivotal issue in the fields of public health, but the evidence in Chinese people is insufficient. Objective: The primary aim of this study is to investigate the association and joint effects of BMI and WC in the risk of heart disease. Methods: A retrospective cohort study was conducted involving 11,700 participants from the China Health and Retirement Longitudinal Study. The incidence of heart disease was collected by following up 9 years. For all analyses, we imputed missing data of the covariates by using multiple imputations. The Cox proportional hazards model and propensity score matching (PSM) were used to exclude confounding factors. The additive interaction test was to explore the joint effect of BMI and WC. Sensitive analysis was to confirm the robust association. Results: During a median follow-up of 8.49 years, 2055 (17.6%) people were diagnosed with heart disease. Upon full adjustment model and after PSM, a positive association was observed between BMI (HR: 1.41, 95% CI: 1.21–1.63), WC (HR: 1.22, 95% CI: 1.09–1.36) and the risk of heart disease. The joint effect (HR: 1.54, 95% CI: 1.34–1.77) of BMI and WC was higher than the simple effect. Subsequent subgroup analysis and sensitivity analyses further confirmed the robustness of the findings, suggesting minimal impact from unmeasured confounders. Conclusions: This cohort study demonstrated a significant association and joint effect between both high levels of BMI as well as high levels of WC and the risk of heart disease among individuals with Chinese people.