We downloaded GWAS summary statistics from UKBB28, BBJ29 and PAGE31 (Data availability). We selected 33 quantitative traits that were available in both UKBB and BBJ, among which 14 were also available in PAGE (Supplementary Table 10). We used 1KG EUR and EAS samples as the LD reference panel for UKBB and BBJ summary statistics, respectively, when constructing PRS. The PAGE study was largely comprised African American and Hispanic/Latino samples, for which we used the 1KG AMR reference panel as an approximation in the PRS analyses. UKBB target data: All UKBB target samples are unrelated UKBB individuals that are non-overlapping and unrelated with the UKBB GWAS sample. To perform population assignment on the UKBB samples, we selected variants that are available in both 1KG and the UKBB genotyped dataset, and removed variants meeting one of the following criteria in 1KG: (i) strand ambiguous; (ii) located on sex chromosomes or in long-range LD regions (chr6: 25–35Mb; chr8: 7–13Mb); (iii) call rate <0.98; and (iv) MAF <0.05. We performed LD pruning on the remaining variants in 1KG using PLINK45 (--indep-pairwise 100 50 0.2),
