Although this is the largest GWAS meta-analysis of smoking phenotypes conducted to date in men and women of African ancestry, statistical power was a significant limitation. We had 80% power (for a mean allele frequency of 0.15 and α of 5 × 10−8) to detect effect sizes of 1.25 for SI, AOI and SC, and a β of 0.15 for CPD. Notably, effect sizes for variants reported with many of these smoking phenotypes reported in the larger GWAS of the European ancestry were much smaller. For example, TAG, ENGAGE and Ox-GSK consortia reported β for SI of 0.015 for SNPs in BDNF and 0.026 for rs3025343 in DBH. Thus, we cannot rule out the possibility of additional loci that influence smoking behavior among African Americans that may be detected with larger sample sizes.
