Association between atherogenic index of plasma and post-stroke epilepsy within one year in patients with acute ischemic stroke: a retrospective cohort study

Introduction Acute ischemic stroke (AIS) is a major cause of death and disability globally. Post-stroke epilepsy (PSE) adversely affects prognosis and quality of life. This retrospective observational study was to explore the association between the atherogenic index of plasma (AIP) and PSE within one year after AIS. Methods This study was a retrospective observational cohort analysis of 20,538 middle-aged and elderly patients with AIS. AIP was calculated as log 10 (TG/HDL). Participants were stratified by AIP levels. Multivariable logistic regression, restricted cubic spline analysis, mediation, stratified and interaction analysis were performed. Results Elevated AIP was significantly associated with higher odds of PSE. A non-linear threshold effect was identified, with an overall inflection point at 0.048 (males: 0.049; females: 0.026), and the association between AIP and PSE was stronger below this threshold. Mediation analysis indicated a reciprocal mediation between fibrinogen and AIP on PSE. Significant multiplicative and additive interactions of AIP with sex, National Institutes of Health Stroke Scale (NIHSS) and hemoglobin A1c (HbA1c) were observed. Significant additive interactions of AIP with C-reactive protein (CRP) were observed. Conclusion Elevated AIP was associated with higher risk of PSE within one year after AIS. This association exhibited sex-specific threshold effects, a bidirectional mediating relationship with fibrinogen, and interactive effects with sex, HbA1c, CRP, and NIHSS. As a simple metric derived from routine lipid profiles, AIP may be useful for risk stratification.