Association of remnant cholesterol inflammatory index and cardiovascular risk among individuals across cardiovascular-kidney-metabolic syndrome stages 0–3: a nationwide prospective cohort study

The remnant cholesterol inflammatory index (RCII) serves as a new biomarker that integrates remnant cholesterol with high-sensitivity C-reactive protein (hsCRP) to reflect both metabolic and inflammatory risk. Its association with incident cardiovascular disease (CVD) in the context of cardiovascular-kidney-metabolic (CKM) syndrome is not well established. This prospective cohort study included 4,606 adults from the China Health and Retirement Longitudinal Study (CHARLS). Cox proportional hazards models were used to estimate associations of baseline RCII, and using a landmark analysis beginning in 2015, cumulative RCII (CumRCII) with incident CVD. Restricted cubic splines were used to assess nonlinearity, and subgroup and sensitivity analyses were performed to assess the robustness of the findings. Over a median follow-up of 7.0 years for baseline RCII, 791 participants developed CVD. A positive association was noted between RCII and the probability of CVD in individuals with CKM syndrome stages 0–3. In the fully adjusted model, the highest versus lowest baseline-RCII quartile had a hazard ratio (HR) of 1.36 (95% CI 1.11–1.67; P = 0.003), the hsCRP-adjusted model gave 1.41 (1.14–1.75; P = 0.002). For cumulative RCII, the 2015 landmark cohort included 4,129 participants, of whom 449 developed CVD; the highest versus lowest CumRCII quartile had an HR of 1.17 (95% CI 0.89–1.54; P = 0.275), which was not significant. Restricted cubic splines suggested a nonlinear positive association for baseline RCII (P for nonlinearity = 0.002). No significant subgroup interactions were observed. Higher baseline RCII was associated with an increased risk of incident CVD among adults classified as CKM stages 0–3, with a nonlinear association. The cumulative RCII association was not significant after the 2015 landmark correction. RCII may be a candidate risk marker of cardiovascular incidents among these individuals. Not applicable.