Because of the large number of male and female smokers, we were able to conduct genome-wide association scans stratified by gender (study), and conduct a genome-wide association scan for differences in genetic effect between men and women. Such analyses are important, because the effect for some loci may differ between men and women or be restricted to one gender, e.g., due to differences in the environment. However, no SNPs achieved genome-wide significance for association with any smoking behavior in either study, and no SNP achieved genome-wide significance for heterogeneity in effect between men and women (between studies).
