Cumulative exposure to the remnant cholesterol inflammation index and incident diabetes mellitus in middle-aged and elderly Chinese adults: A nationwide cohort study from CHARLS.

The remnant cholesterol inflammation index (RCII) is a novel biomarker integrating remnant cholesterol and high-sensitivity C-reactive protein. Whether long-term exposure to RCII is associated with diabetes mellitus (DM) remains unclear. We examined the association between cumulative RCII (cumRCII) exposure and incident DM risk in the China Health and Retirement Longitudinal Study. We included 5817 participants with DM at baseline from the China Health and Retirement Longitudinal Study 2011 to 2015. Logistic regression models and restricted cubic splines were used to examine the relationship between cumRCII and DM risk, adjusting for potential confounding factors. Subgroup analysis was used to examine potential effect modification, and sensitivity analysis was used to test the robustness of the primary findings. A total of 786 new-onset DM cases occurred. Participants in the highest quartile of cumRCII levels had a higher DM risk than those in the lowest quartile (odds ratio = 2.47; 95% confidence interval = 1.95-3.12; Ptrend < .001). Each 1-SD increment in cumRCII was associated with a 25% increased risk (odds ratio = 1.25; 95% confidence interval = 1.18-1.33). Restricted cubic spline analysis indicated a positive and nonlinear association between cumRCII and DM (Pfor overall < .001; Pfor nonlinearity < .001). Subgroup analysis revealed consistent associations between cumRCII and DM risk (all Pfor interaction > .05). E-value analysis suggested robustness to unmeasured confounding. Elevated long-term cumRCII is significantly associated with higher DM risk in middle-aged and elderly Chinese adults, suggesting that cumRCII may serve as a potential biomarker for identifying individuals at higher metabolic risk.