The strengths of our study include the large population size and comprehensive SNP coverage of the genes investigated. In addition, the use of a single racial/ethnic group and population stratification analysis with 200 independent SNPs allows us to eliminate the possibility that population substructure may contribute to our findings. However, the minor allele frequency for rs16969968 is very low in non-European populations (<5%), suggesting that the impact of this SNP will be far less in other populations.
