Association of triglyceride glucose index combined with obesity indicators with cognitive impairment

The association of a combination of the TyG index and obesity markers, specifically waist circumference (WC), with cognitive function is unknown. This research investigated the relationship between TyG-WC measurements and cognitive impairment in a low-income population in China; moreover, this study evaluated the role of diabetes mellitus and body mass index (BMI) in modulating this relationship.

1125 eligible individuals aged ≥ 60 years participated in this study. The TyG index and obesity indicators (BMI, WC, and waist-to-height ratio) were calculated for individual participants and categorized into quartiles. Multivariate logistic regression analysis was used to evaluate the correlation between TyG-WC values and cognitive impairment; the possibility of a nonlinear relationship was explored using constrained cubic spline analysis. The participants were divided into different groups according to their diabetes status and BMI category for subgroup analyses. Linear regression was used to investigate the correlation between TyG-WC values and MMSE scores.

The prevalence of cognitive impairment in the study participants was 47.3%, with a significant negative association between TyG-WC values and cognitive impairment, (odds ratio [OR] = 0.999; 95% confidence interval [CI], 0.997-1.00, P = 0.009). A U-shaped correlation was observed between the TyG-WC values and cognitive impairment (P = 0.008). Subgroup analyses showed that the inverse association between TyG-WC values and cognitive impairment was stronger in non-diabetic individuals (OR = 0.998; 95% CI, 0.997-0.999; P = 0.002) and in those with a lower BMI (< 24 kg/m²; OR = 0.996; 95% CI, 0.994-0.998; P = 0.001). A positive correlation was found between TyG-WC values and MMSE scores, particularly in men and non-diabetic individuals (β = 0.003; 95% CI, 0.0002-0.005; P = 0.031).

This study demonstrates a nonlinear U-shaped relationship between TyG-WC values and cognitive function. The stronger inverse association between TyG-WC values and cognitive decline in the non-diabetic and low-BMI subgroups suggests that these populations may benefit the most from targeted interventions. These findings are important for clinical practice and formulating disease-prevention policies, emphasizing the need for metabolic health management to prevent cognitive decline, particularly in low-income populations.