Cumulative average remnant cholesterol inflammatory index and risk of cardiometabolic multimorbidity: evidence from a prospective nationwide cohort study in China

BACKGROUND: Cardiometabolic multimorbidity (CMM) poses a major health burden in aging populations. The long-term effect of cumulative remnant cholesterol inflammatory index (RCII) on CMM remains unclear. This study aimed to examine this relationship among middle-aged and older Chinese adults. METHODS: This retrospective longitudinal cohort included 5,150 participants aged ≥ 45 years without baseline CMM from the China Health and Retirement Longitudinal Study. The cumulative average natural log-transformed RCII (cumlnRCII) was calculated from 2011 to 2015. RCII was defined as (remnant cholesterol × high-sensitivity C-reactive protein)/10. Incident CMM was defined as the new onset of at least two of the following conditions: diabetes, heart disease, or stroke by 2018. Multivariate Cox and logistic models were used to estimate the hazard ratio (HR) and odds ratio (OR), with restricted cubic splines used to test dose-response relationships. Subgroup and sensitivity analyses were conducted to ensure the reliability of the results. RESULTS: Over a median follow-up period of 7 years, 294 participants developed CMM. The incidence of CMM increased across cumlnRCII tertiles: 3.2% (Tertile 1), 5.2% (Tertile 2), and 8.7% (Tertile 3). After adjustment, compared with Tertile 1, Tertile 3 had significantly greater risks (OR = 2.14, 95% CI: 1.55-2.99; HR = 2.10, 95% CI: 1.53-2.89). Each 1-standard deviation increase in cumlnRCII was associated with a 33% higher odds and a 32% higher risk of CMM. A linear dose-response correlation was identified (P-nonlinear = 0.383). Most subgroups exhibited consistent associations, and sensitivity analyses validated the reliability of the results. CONCLUSIONS: The cumulative average RCII is independently associated with increased CMM risk, underscoring its value for identifying high-risk individuals, guiding preventive strategies, and advancing efforts toward healthy aging by reducing the burden of cardiometabolic disease.