STUDY DESIGN AND SETTING: We searched bibliographic databases, dissertations, and trial registries from inception to September 10, 2025, for routine-care studies reporting adherence or persistence to secondary prevention medications after ischemic stroke or transient ischemic attack. Cutoff-based proportions were extracted. We used 3-level hierarchical Bayesian models to characterize heterogeneity and multivariable meta-regression to evaluate associations with measurement specifications, follow-up window, medication class, region, and study-level characteristics. From the fitted model, we derived estimates standardized to a prespecified reference specification: pharmacy or administrative data, moderate definition stringency, and a 9- to 15-month follow-up window.

RESULTS: The review included 141 studies; 101 (432 estimates; 976,020 participants) contributed to the quantitative synthesis. Unstandardized pooled estimates suggested that 74.1% of patients were adherent and 76.8% were persistent. Heterogeneity was substantial, with explained variation concentrated more in the measurement-related Assessment and Administration domains than in reported Patient characteristics. Under the common reference specification, the model-based estimates were lower, at 53.7% for adherence and 48.2% for persistence. Standardized persistence declined from 63.3% at 1 to 4 months to 28.1% beyond 30 months. Adjusted estimates were generally lower in Asia; persistence was numerically lowest for anticoagulants, although credible intervals were wide and overlapping.