genetically similar to reference populations from Africa (ie, AA)36 (COGA sample removed). Because PRS-CSx improves predictive power for non-European ancestry samples with smaller GWAS,35 we included both the European and African ancestry–derived polygenic scores in the AA sample in COGA, but only the European ancestry–derived polygenic scores in the EA sample in COGA. To account for population stratification, we regressed polygenic scores on the first 10 genetic similarity principal components (PC1-PC10) within each group (EA and AA) and used the residualized standardized polygenic scores in analyses.
