Finally, as the α4β2 nAChR is the most widely distributed subtype nAChR, we investigated the interaction effect of the 11 SNPs genotyped within the CHRNA4 gene and rs2072661 at EOT and at 6-month follow-up. None of the interaction tests were significant at an α-level of 0.05. For example, within individuals with the WT genotype for rs2236196, a known functionally significant SNP in CHRNA4 (14), the CHRNB2 SNP rs2072661 effect reduced quit rates (OR = 0.39; 95% CI 0.24–0.65). In contrast, for those individuals with a minor allele for rs2236196, the impact on quit rates was negligible (OR = 0.89; 95% CI 0.31–2.50). While qualitatively suggestive, the P-value for the interaction test was only 0.11. At 6-month follow-up, the effect of rs2072661 did not differ by CHRNA4 rs2236196 carrier status.
