Evidence from two large prospective cohorts: variations in remnant cholesterol inflammation index and the risk of cardiometabolic multimorbidity in middle-aged and elderly populations.
OBJECTIVE While residual cholesterol (RC) and high-sensitivity C-reactive protein (hs-CRP) are independent risk factors for cardiometabolic multimorbidity (CMM), their combined predictive value remains unclear. We investigated the predictive utility of the remnant cholesterol inflammation index (RCII) for CMM incidence. METHODS The RCII was derived from 5,870 participants in the China Health and Retirement Longitudinal Study (CHARLS) and 2,295 in the English Longitudinal Study of Ageing (ELSA), calculated as RC (mg/dL) × hs-CRP (mg/L) / 10. Longitudinal analyses in a subcohort (n = 5,966) further assessed the associations between cumulative RCII, changes in RCII and CMM incidence. RESULTS Each ln-unit increase in baseline RCII was associated with a 14% (CHARLS: HR 1.14, 95% CI 1.09-1.19) and 21% (ELSA: HR 1.21, 95% CI 1.10-1.34) higher CMM risk. Similarly, cumulative RCII increments raised CMM risk by 20% (CHARLS: HR 1.20, 95% CI 1.11-1.29) and 30% (ELSA: HR 1.30, 95% CI 1.11-1.51). Transition patterns analysis showed that stable high RCII levels conferred the highest CMM risk compared to stable low RCII levels. RCII demonstrated moderate independent predictive capability for CMM and outperformed RC or hs-CRP alone. CONCLUSION By integrating lipid and inflammatory pathways, the RCII was significantly associated with incident CMM and may enhance early risk stratification.