Association between remnant cholesterol inflammatory index and dementia: a longitudinal observational study

The remnant cholesterol inflammatory index (RCII) is a comprehensive assessment of remnant cholesterol and low-grade inflammation, but the association between RCII and dementia remains unclear. We aimed to investigate the association between RCII and dementia among Chinese adult males and females. From the China Health and Retirement Longitudinal Study, 5,633 dementia-free adults aged ≥ 45 (mean age 62.15 ± 7.00 years; 2668 [51.36 %] female) at baseline (2011-2012) were followed up until 2018 to detect incident dementia. Dementia was ascertained based on cognitive batteries and the Activity of Daily Living scale. RCII was calculated by the formula: RCII = RC (mg/dL) × hs-CRP(mg/L)/10 and then quartiled. Data were analyzed using logistic regression. During the follow-up, 787 (13.97 %) participants developed dementia. In multivariable-adjusted logistic regression, highest quartile of RCII was associated with an increased risk of dementia, compared to the lowest quartile. After stratifying by sex, a significant association between high RCII and dementia was observed only in females, but not in males. Moreover, a significant multiplicative interaction between high RCII and sex was detected. In conclusion, high RCII is associated with higher risk of dementia, particularly among females. These findings suggest that RCII could be a valuable early indicator for identifying individuals at high risk for dementia.