Figure 6: Cross-population PRS results for UK Biobank East Asians when incorporating both European and non-European training data.

We report average prediction accuracy (relative-R²; see main text), meta-analyzed across 7 well-powered, independent traits, for PRS trained in UK Biobank British (average N=325K) and Biobank Japan samples (average N=124K; used by PolyPred+ and its summary statistic-based analogues only) and applied to UK Biobank East Asians. The target population sample size is indicated in parentheses; PolyPred, PolyPred+, and their summary statistic-based analogues used 500 additional training samples from the target population to estimate mixing weights. Asterisks above each bar denote statistical significance of the difference vs. BOLT-LMM, with black asterisks denoting an advantage and red asterisks denoting a disadvantage (*P<0.05; **P<0.001). P-values were computed using a two-sided Wald test and were not adjusted for multiple comparisons. Errors bars denote standard errors. Numerical results, results for all 23 traits analyzed, absolute prediction accuracies (R²), and P-values of relative improvements vs. BOLT-LMM are reported in Supplementary Tables 4–6.