Association between metabolic score for insulin resistance and cognitive impairment in Chinese middle-aged and older adults: Findings from the CHARLS study

Background Cognitive impairment (CI), an early sign of Alzheimer's disease, may be identified using the metabolic score for insulin resistance (METS-IR), a novel insulin resistance marker. Objective This nationwide cohort study in China examined the association between METS-IR and CI in middle-aged and older adults, providing preliminary evidence for early prevention. Methods Data were obtained from the China Health and Retirement Longitudinal Study (CHARLS) 2011–2015. METS-IR was calculated using fasting plasma glucose, triglycerides, body mass index, and high-density lipoprotein cholesterol. CI was evaluated through episodic memory and mental status. Descriptive statistics, multivariable logistic regression, restricted cubic spline (RCS), subgroup, and interaction analyses were used to assess the association of METS-IR with CI, with sensitivity analysis confirming robustness. Results The study included 5842 middle-aged and older adults in China. The incidence of CI throughout the follow-up period was 14.36%. The multivariable logistic regression models indicated that participants in Q3 and Q4 of METS-IR had 1.375-fold and 1.564-fold higher risks of CI, respectively, compared with those in Q1 (Q3: OR = 1.375, 95% CI = 1.075–1.758; Q4: OR = 1.564, 95% CI = 1.220–2.005). The trend analysis of METS-IR was also statistically significant. A substantial linear relation between METS-IR and CI was confirmed by the RCS analysis (p for nonlinearity = 0.462). Moreover, consistent associations were observed across extensive subgroup analyses. Conclusions Elevated METS-IR levels were significantly associated with increased CI risk in middle-aged and older Chinese adults. These findings provide support for early identification and intervention of CI.