as weights was never optimal. Our simulation studies were performed in simplified scenarios in which admixture arises from only two ancestral populations (unlike the HCHS/SOL, in which there are three ancestral populations), and the effect sizes were the same in both ancestries, and in the admixed populations themselves. The LD patterns between our simulated training and testing admixed populations were more similar to each other than to the LD pattern in the simulated EA population, despite the fact that the two admixed populations had different admixture proportions. Therefore, given large enough sample sizes, we expect that the training admixed population would have been a better reference for PRS construction in the testing admixed population compared to the EA population. However, in these simulations usually the PRSs with SNP selection using EA GWAS and weights using META performed best, and weights using the admixed training datasets usually performed poorly. These results are supported by Dudbridge (2013), who suggested that many thousands of individuals are required to effectively calculate effect sizes to be used as SNP weights.
