In addition, the issue of admixture within ethnic groups has been identified as an increasingly important factor to consider in US ethnic groups including Native Americans78 and Blacks79, but admixture rates also vary across other ethnic groups and studies also differ in their inclusion criteria for ethnic group membership (e.g., 50%, 75%, full heritage required). Both sample and study characteristics have been shown to moderate gene effect sizes80, and as ethnic groups become less homogeneous, the issue of admixture may further affect ability to detect genetic-phenotypic relationships. The use of ancestral identification markers to estimate admixture proportion allows admixture to be used as a covariate to reduce genetic heterogeneity and enhance detection of genetic associations79.
