samples (r2 between rs2036527 and rs1979905=0.443 in CEU, 0.045 in YRI and 0.064 in STOMP). The additional signals at 15q25.1 with near genome-wide significance in our study are represented by rs667282, rs938682 and rs3813570, which are weakly correlated with rs2036527 (r20.2 in CEU, 0.12 in YRI and 0.084 in STOMP). These three SNPs are correlated with each other (r20.60 in CEU and 0.32 in YRI) as well as with rs578776 and other SNPs at 15q25.1 that define a signal for smoking intensity in the European ancestry populations that is independent of rs2036527.8 However, when conditioning on rs2036527 in the four largest study populations in our sample (the African American GWAS consortia of Prostate Cancer, African American GWAS consortia of Breast Cancer, Candidate Gene Association Resource and Women's Health Initiative; n=13 113), the association between these three SNPs and CPD diminished (P-values of 10−3 after conditioning on rs2036527; Supplementary Figure 2). Assuming the GWAS arrays utilized in this study provide adequate coverage of common alleles at 15q25.1, this suggests there are not multiple independent signals for CPD in this region in African Americans or the frequencies of the functional alleles and/or their effect sizes are much smaller than the signal defined
