Longitudinal Associations Between the Atherogenic Index of Plasma and Frailty Progression in Adults Aged 45 Years and Older: Evidence from the China Health and Retirement Longitudinal Study

Qifan He¹Wenjing Yan²Qianyi Ma²Hongwei Liu^3*Haixia Fan^4*

• ¹Haining People's Hospital, Jiaxing, China
• ²Shanxi Normal University, Linfen, Shanxi Province, China
• ³Taiyuan Central Hospital, Taiyuan, Shanxi Province, China
• ⁴First Hospital of Shanxi Medical University, Taiyuan, Shaanxi, China

The atherogenic index of plasma (AIP), a lipid metabolism marker, is associated with cardiovascular disease and insulin resistance, but its role in frailty progression remains unclear. This study aims to investigate the association between the atherogenic index of plasma (AIP) and frailty progression in middle-aged and older adults.Utilizing longitudinal data including 6,558 adults aged ≥45 years from the China Health and Retirement Longitudinal Study (CHARLS), we assessed AIP at two time points (2011-2012 and 2015) and calculated cumulative AIP. Frailty was measured via a 30-item Frailty Index (FI), and Group-based trajectory modeling (GBTM) was employed to categorize frailty progression. Participants were Clustered by AIP change patterns using K-means clustering. Multivariable logistic and Cox regression models estimated associations between AIP metrics and frailty outcomes. A mixed-effects linear model explored the relationship between AIP and FI progression, while restricted cubic spline (RCS) curves assessed potential nonlinear associations. Mediation and subCluster analyses examined underlying mechanisms and effect variations.Three AIP change patterns and two FI progression trajectories were identified. Higher baseline, cumulative, and increasing AIP levels were consistently associated with an accelerated frailty trajectory and greater risk of incident frailty. In fully adjusted models, those in the highest quartile of AIP had significantly increased odds and hazard ratios for frailty (e.g., baseline AIP OR = 1.51, HR = 1.42). Mixed-effects models confirmed that higher and increasing AIP predicted steeper FI increases over time. RCS analysis revealed a nonlinear relationship between baseline AIP and frailty incidence. Glycosylated hemoglobin and glucose emerged as key mediators, explaining a significant proportion of the observed associations.Cluster 删除[heqifan]: Conclusion: Elevated AIP levels were significantly associated with accelerated frailty progression and increased frailty risk in adults aged 45 years and older. Optimizing AIP through sustained regulation of triglyceride and high-density lipoprotein cholesterol homeostasis may help mitigate frailty progression in aging populations.