Beyond these practical considerations that contributed to a focus on populations of European ancestry, specific population-genetic properties of the European population have facilitated the successes of GWA studies in groups of European origin. Allele-frequency variation across populations — a source of false-positive findings in association studies19,20,21 — is less pronounced in Europe than in other geographic regions22,23,24,25,26,27. Although large population-genetic studies have detected subtle geographic gradients in allele frequencies across the European continent28,29,30 as well as within individual countries31,32, well-designed GWA studies in Europeans have generally been able to control for the effects of underlying allele-frequency variation, and they generally have not identified false positives owing to population structure as a significant problem.
