our study of 0.03 s.d. unit of BMI for rs8050136, we had only 32 and 3.6% power to detect association at α-level of 0.05 and 0.0011, respectively. On the other hand, our strongest association observed was for rs9424977 at NEGR1 (P = 0.005 in the meta-analysis, Table 2). The effect size of this SNP in our samples is 0.06 s.d. unit of BMI, and given the BMI-increasing allele frequency of 0.46, we had an estimated 85 and 39% power to detect association at α-level of 0.05 and 0.0011, respectively. In general, we have good power (≥80%) to detect an effect size of 0.06 s.d. unit of BMI with an allele frequency of at least 0.40 at α-level of 0.05. However, after correction for multiple testing, we would need more than 10 000 samples to have comparable power. Given the prior association of these SNPs in European studies, we primarily presented significance levels without multiple comparisons to enhance study power. Our findings may reflect both allelic and locus heterogeneity in African Americans as compared with the European-derived populations. Larger sample sizes and thorough examination of these loci will be required to determine their effects in African Americans.
