The effects of a body shape index and remnant cholesterol inflammatory index on incident cardiovascular diseases: insights from a nationwide cohort study

While a body shape index (ABSI) and remnant cholesterol inflammatory index (RCII) are established cardiovascular risk factors, their joint, interactive, and mediating effects with incident cardiovascular diseases (CVD) remain poorly characterized. This prospective investigation examined how ABSI and RCII might influence CVD incidence. This prospective analysis leveraged nationally representative data from the China Health and Retirement Longitudinal Study (CHARLS), encompassing 7,780 participants aged ≥ 45 years without CVD at baseline. ABSI and RCII served as primary exposures. Incident CVD (heart diseases or stroke) were identified through guideline-based diagnosis or verified self-reports. Analyses were performed using SPSS software v.25.0 and R software v.4.4.4. Out of 7,780 individuals, 560 (25.48%) developed CVD. Compared to the first quartile of ABSI, the adjusted hazard ratios (HRs) for CVD in the second, third and fourth quartile were 1.26 [95% confidence interval (CI): 1.10–1.44], 1.15 [95% CI: 1.00-1.32], and 1.20 [95% CI: 1.04–1.38], respectively. High RCII group conferred a 1.19-fold higher risk [95% CI: 1.09–1.31] versus low RCII group. When participants were stratified into eight groups by ABSI quartiles and RCII quartiles, the second ABSI quartile with high RCII showed the highest HR of 1.43 [95% CI:1.20–1.72], while the fourth ABSI quartile with high RCII had the greatest absolute CVD incidence. The proportion of RCII’s mediating effects in the second, third, and fourth quartiles of ABSI was 5.00%, 12.84%, and 17.17%, respectively. Compared with traditional models, the area under curve of ABSI, RCII, and ABSI + RCII to predict incident CVD were 0.643, 0.644, and 0.645, respectively. ABSI and RCII demonstrate joint effects on CVD and serve as valuable tools for improving cardiovascular risk stratification among middle-aged and elderly Chinese population. RCII partially mediates the association between ABSI and CVD. Their combined use, particularly in identifying high-risk subgroups, supports the development of more targeted and efficient preventive strategies, which is crucial for alleviating the growing burden of CVD within aging populations.