The minor alleles of eight of the statistically significant SNPs were associated with an increased risk of heavy smoking (Table 2, highlighted with a black background). Seven of these SNPs (all but rs1996371) share a high degree of linkage disequilibrium (LD, D' between 0.81 and 1.0, r2 between 0.61 and 0.99). The rs1996371 SNP is also in LD with the other 7 SNPs, although less so (D' between 0.55 and 0.72, r2 between 0.22 and 0.39). The association between rs1996371 and heavy smoking was completely attenuated (per allele OR = 1.02, 95% CI: 0.89, 1.18) when any other of the risk SNPs in this group were included in the logistic regression model. Thus, these eight SNPs represent a single correlated cluster that is very significantly associated with increased risk of heavy smoking.
