Association between triglyceride glucose (TyG)-atherogenic index of plasma (AIP) index and new-onset stroke risk in middle-aged and older Chinese individuals: a nationwide prospective cohort study

The triglyceride-glucose (TyG) index serves as an established indicator of insulin resistance, while the atherogenic index of plasma (AIP) functions as a reliable marker for dyslipidemia. Nevertheless, the synergistic impact of the combined TyG-AIP index on cerebrovascular events remains insufficiently understood. This investigation explored the relationships between longitudinal variations in the TyG-AIP index and cumulative exposure, baseline characteristics, as well as incident stroke risk among Chinese middle-aged and elderly populations. The analysis encompassed 6,987 participants aged 45 years and above from the China Health and Retirement Longitudinal Study (CHARLS), with emphasis on initial TyG-AIP measurements (2011), follow-up TyG-AIP values in 2015, and aggregate TyG-AIP scores calculated from these assessments. The temporal variations of the TyG-AIP index were categorized into three distinct groups through K-means cluster methodology. Logistic regression approaches were utilized to explore the association between TyG-AIP index levels and incident cerebrovascular events. Restricted cubic spline (RCS) analysis was implemented to evaluate potential non-linear associations, whereas receiver operating characteristic (ROC) analysis determined the discriminative performance. Throughout the 5-year observation period (2015 to 2020), cerebrovascular events occurred in 340 participants (4.87%). The stroke occurrence rates across Clusters 1, 2, and 3 were 5.96%, 3.87%, and 5.52%, respectively. Following adjustment for potential confounders, Cluster 1 characterized by moderate and declining TyG-AIP values (OR = 1.471, 95% CI 1.030–2.100) and Cluster 3 featuring elevated and ascending TyG-AIP levels (OR = 1.604, 95% CI 1.204–2.137) both demonstrated heightened risk for incident cerebrovascular events relative to Cluster 2. The third quartile group exhibiting high aggregate TyG-AIP values (OR = 1.393, 95% CI 1.038–1.869) and the third quartile group with elevated initial TyG-AIP levels (OR = 1.396, 95% CI 1.052–1.854) were similarly linked to augmented stroke risk. The RCS examination indicated a non-linear association between aggregate TyG-AIP values and cerebrovascular risk (P for non-linearity = 0.047). ROC evaluation revealed that the TyG-AIP index possessed enhanced discriminative capacity relative to standalone TyG or AIP parameters. Temporal variations in initial and aggregate TyG-AIP values demonstrate independent associations with heightened cerebrovascular risk among Chinese middle-aged and elderly populations. The TyG-AIP index shows a nonlinear association with stroke risk and is anticipated to be a more efficient and significant indicator for evaluating early stroke risk compared to individual metabolic indices.