Association of the atherogenic index of plasma with frailty in U.S. adults: a cross-sectional study based on NHANES

Frailty is a multifactorial syndrome associated with adverse health outcomes. The metabolic underpinnings of frailty, particularly lipid metabolism, are not fully understood. Unlike isolated lipid fractions or inflammatory markers, atherogenic index of plasma (AIP) integrates atherogenic lipid profiles and systemic inflammation. However, its association with frailty has not been extensively studied. Six thousand four hundred participants from the National Health and Nutrition Examination Survey (NHANES) were enrolled. Frailty was calculated with the frailty index (FI), with scores ≥ 0.21 indicating frailty. Logistic regression adjusted for demographic, socioeconomic, and lifestyle factors evaluated the association between AIP and frailty. Restricted cubic splines (RCS) explored nonlinear associations, and subgroup analyses assessed interactions across age, sex, race, poverty income ratio, smoking status, drinking status, and marital status. This study demonstrated a strong dose-response relationship between AIP and frailty. After full adjustment, Individuals in quartile 3 and 4 showed higher odds of frailty than those in lowest quartile, with ORs (95% CI) of 1.26(1.01,1.57) and 1.73(1.34,2.23), respectively. Continuous AIP measures also exhibited significant associations (OR: 1.82, 95% CI: 1.34-2.47). RCS analysis showed that AIP exhibited a nonlinear association with the risk of frailty. Subgroup analyses showed the associations were more pronounced in the females. The sensitivity analyses substantiated the stability and strength of the results. Our findings suggest that elevated AIP levels are independently associated with frailty risk, particularly in females, highlighting its potential as a cost-effective biomarker for risk stratification. Future longitudinal studies are needed to validate AIP's predictive utility and uncover the underlying mechanisms.