We used two approaches to assess effect heterogeneity within PAGE participants. First, we used interaction analyses with models that included variant by PC (SNP × PC) interaction terms for all 10 PCs. The fit of nested models was compared using the F-statistic, for which the associated interaction P value indicated whether the inclusion of the 10 SNP × PC interaction terms improved the model fit compared to a model that lacked the interaction terms. The overall SNP × PC interaction P values evaluated whether the additional variance explained by variant × genetic ancestry interactions was statistically significant and represented effect modification driven by genetic ancestry. Interaction P values for all novel and secondary findings are included in Supplementary Table 3.
