Racial differences in COPD may exist88,89. Thus, we also examined the case-control results only in the African-Americans. While underpowered, these results did not reveal any novel genome-wide significant loci (Table S8); furthermore, at the loci described in this work, there was no convincing evidence of heterogeneity (Tables 3 and 4) or differential effect sizes compared with those in non-Hispanic whites (Table S4 and S5). These data are consistent with a prior report finding little evidence that the relationship of smoking to lung function differed by genetic ancestry90, as well as genetic studies of other traits that have demonstrated overall similarities of loci shared between ethnically diverse groups91,92. While these results support our decision to combine the African-Americans and non-Hispanic whites to improve statistical power, our results should not be interpreted to imply including other ethnic groups is generally redundant; indeed, genetic studies in specific ethnic groups have led to discovery of novel loci93 and provided important information for identifying specific variants at individual loci91,94.
