Longitudinal correlation between cumulative remnant cholesterol inflammatory index and incident diabetes

Diabetes is closely associated with dyslipidemia and inflammation. However, studies on the combined effects of inflammation and dyslipidemia on incident diabetes are lacking. Remnant cholesterol inflammation index (RCII) is a clinical indicator of inflammation and dyslipidemia. In this study, we aimed to investigate the longitudinal relationship between cumulative RCII (cumRCII) and incident diabetes. Data were sourced from the China Health and Retirement Longitudinal Study from 2011 to 2018. The mean age of the study participants was 58 years. CumRCII was treated as the exposure variable and incident diabetes as the outcome variable. Restricted cubic splines and logistic regression were used to evaluate the relationship between cumRCII and incident diabetes, and longitudinal targeted maximum likelihood estimation used for sensitivity analysis. A total of 4,513 participants were included in the analysis. During a 7-year follow-up period, 302 cases of incident diabetes were diagnosed. Using the first quartile of cumRCII as the reference, the odds ratio (OR) for incident diabetes in the fourth quartile was 2.60 (OR = 2.60; 95% confidence interval [CI], 1.74–3.87; P < 0.001). Each standard deviation increase in cumRCII, the OR for incident diabetes was 1.26 (OR = 1.26; 95% CI, 1.16–1.37; P < 0.001). Sensitivity analysis yielded consistent conclusions, with the Net Reclassification Improvement (NRI) for the model incorporating cumRCII being 0.346 and the DeLong test showing statistical significance. We found a nonlinear relationship between cumRCII and incident diabetes, the threshold value of cumRCII with respect to incident diabetes was 43.39. CumRCII is closely associated with incident diabetes in adults aged ≥ 45 years, and a significant correlation was found between cumRCII and incident diabetes in the population with normal triglyceride levels. Furthermore, the longitudinal relationship between cumulative RCII and incident diabetes was non-linear. CumRCII can be used as an early indicator of incident diabetes in a population with normal triglycerides. This study confirmed that cumulative remnant cholesterol inflammation index (cumRCII) is closely associated with incident diabetes in adults aged 45 years and older. Furthermore, a close correlation exists between cumRCII and incident diabetes in the population with normal triglyceride levels.