Remnant Cholesterol Inflammatory Index and New-Onset Diabetes in Middle-Aged and Older Adults: Evidence From Prospective Surveys of Chinese and UK Populations.

Aim: The aim of this study was to investigate the relationship between remnant cholesterol inflammatory index (RCII) and new-onset diabetes mellitus in middle-aged and elderly populations in China and United Kingdom. Methods: The total number of participants included in this study was 9946, comprising members of the Chinese Health and Retirement Longitudinal Study (CHARLS) cohort and the English Longitudinal Study of Ageing (ELSA) cohort. A comparison was made of the baseline characteristics of the two cohorts. Subsequently, a cox regression analysis was performed on the risk factors for diabetes. Subgroup analyses were conducted to explore the potential for effect modification across diverse subgroups. Results: The application of RCII quartile analyses revealed that the risk observed in the highest quartile (Q4) within the ELSA cohort was 8.49 times higher than that recorded in the lowest quartile (Q1). This finding was particularly significant for males. Similarly, the risk in the CHARLS cohort was 3.1 times higher than that in Q1. Following multi-model adjustment, the risk of diabetes exhibited a progressive increase from the second to the fourth quartile of RCII levels in both cohorts, with all associations demonstrating statistical significance. For each 1 kg/m2 increase in body mass index (BMI), the risk of diabetes increased by 13% in the ELSA cohort and by 15% in the CHARLS cohort. Subgroup analyses revealed that within the CHARLS cohort, the association between RCII and diabetes was more pronounced among non-obese individuals, whereas in the ELSA cohort, this link was more evident among middle-aged adults. Conclusions: Elevated RCII levels have been demonstrated to be significantly associated with an increased risk of future diabetes in middle-aged and older adults.