Development and External Validation of a Machine Learning Model for 10-Year Ischemic Stroke Risk Prediction in Diverse Populations.

Importance: Machine-learning models for ischemic stroke risk prediction are rarely validated across ancestrally distinct cohorts, and the contributions of polygenic risk scores (PRS) and self-reported race in such models remain unclear. Objective: To develop and externally validate a 10-year ischemic stroke risk model and quantify the incremental contributions of laboratory trajectories, PRS, and self-reported race and ethnicity across populations. Design Setting and Participants: Retrospective cohort study with model development in the All of Us (AoU) Research Program (n = 34,987; 1,920 incident strokes) and external validation in the Bio Exposures: Three XGBoost model tiers added laboratory feature trajectories (M2) and 20 PRS (M3) to clinical baseline features (M1); evaluated under race-blind and race-aware specifications. Main Outcomes and Measures: First inpatient ischemic stroke within 10 years; discrimination (area under the receiver operating characteristic curve [AUROC]) and calibration (observed-to-expected [O/E] ratio). Results: In the AoU test partition (n = 6,998; 384 cases), M3 achieved AUROC 0.813 (95% CI, 0.788-0.837), outperforming the Revised Framingham Stroke Risk Profile (ΔAUROC 0.164) and Pooled Cohort Equations (ΔAUROC 0.181; both Conclusions and Relevance: A machine-learning ensemble combining clinical, laboratory, and polygenic features outperformed traditional risk scores by 0.16-0.18 AUROC and retained discriminative validity in an ancestrally distinct external cohort but required site-specific recalibration of absolute risk. The marginal contribution of self-reported race overlapped with polygenic signal, supporting per-ancestry calibration over universal race-aware model deployment.