There are several strengths of this study. First, although significant associations of variants within the CHRNA5/A3/B4 cluster with smoking have been replicated in multiple independent samples, almost all these studies were concentrated on smoking dependence in samples of European origin [14], [18], [19], [20], [21], [22], [23], [24], [25]. Very recently, relatively weak associations of some variants of this gene cluster with ND were reported in two African American samples [18], [28]. Among the 76 SNPs investigated by Saccone et al. [28], eight showed nominally significant association with ND (P value = 0.0147∼0.0443), with rs16969968 in CHRNA5 being the strongest, at a P value of 0.0147. Similarly, in a prior study [18], we analyzed 22 SNPs within the gene cluster and found that only rs8040868 in CHRNA3 showed a nominally significant association with ND (P = 0.017∼0.039). However, none of these associations survived correction for multiple testing in the two African American samples [18], [28]. Although there were two studies investigating potential associations of variants in the gene cluster with LC and smoking in Chinese [44] and Japanese [45] subjects,
