Our third important result involves rs578776 and its correlates. These SNPs represent an established association in European-descent populations that has only low correlation with rs16969968 (r2 < 0.25) and whose minor allele is elevated in controls. In our sample, rs578776 is associated with nicotine dependence in European-Americans as expected, but is not associated in African-Americans. Furthermore, we detect significant heterogeneity in the odds ratios for rs578776 and some correlates (p ~ 0.01). These results suggest that those SNPs are not the biologically causal variants explaining the statistical association. Recently, rs6495309 and other SNPs correlated with rs578776 in HapMap CEU but not in HapMap JPT and CHB [35] were associated with lung cancer and smoking in a Chinese population [36].
