used unconditional logistic regression, adjusted for the same covariates. These tests were conducted separately for PLCO and NHS. For SNPs that passed QC filters and had minor allele frequency above 1% in both studies, we combined evidence for association across PLCO and NHS using weighted Z-scores [56]. Heterogeneity in SNP-smoking behavior associations across study was assessed using Q and I 2 statistics [57]. Power calculations were performed using Quanto (http://hydra.usc.edu/GxE/)[58]
