Remnant Cholesterol Inflammatory Index and its Association With Cardiometabolic Multimorbidity in Middle-Aged and Advanced-Aged Individuals: Evidence From the China Health and Retirement Longitudinal Study.

BACKGROUND The association between remnant cholesterol inflammatory index (RCII) and cardiometabolic multimorbidity (CMM) remains unclear. RCII is defined as: {Total Cholesterol - (High-Density Lipoprotein Cholesterol + Low-Density Lipoprotein Cholesterol)] × High-Sensitivity C-Reactive Protein/10}. This study examined the association between baseline RCII and CMM among middle-aged and older adults in China. MATERIAL AND METHODS This study analyzed data from the China Health and Retirement Longitudinal Study (CHARLS), including 6173 participants. CMM was defined as the coexistence of at least 2 of 4 conditions: hypertension, diabetes, heart disease, or stroke. Participants were grouped according to the quartiles of natural log-transformed RCII (lnRCII) values. Modified Poisson regression models, restricted cubic splines, and receiver operating characteristic curves were used to examine the relationship between lnRCII and CMM outcomes. RESULTS In the cohort, 1832 cases of CMM occurred, and the incidence of CMM was highest in the lnRCII highest-quartile group (P<0.001). In the fully adjusted model, each unit of increase in lnRCII was associated with a higher risk of CMM (RR=1.13, 95% CI: 1.09-1.16), and participants in the highest quartile had a higher risk than those in the lowest quartile (RR=1.69, 95% CI: 1.50-1.90). The area under the curve for lnRCII was 0.607 (95% CI: 0.592-0.622), indicating modest discriminatory ability. CONCLUSIONS Higher baseline lnRCII was associated with an increased risk of incident CMM in middle-aged and older Chinese adults. Although RCII may capture combined information on remnant cholesterol and inflammation, its clinical predictive value requires further validation.