The demographic characteristics of GWAS subjects are shown in Table 1. There was little evidence of systemic P-value inflation (genomic inflation factor λ < 1.029) for the EA, AA or EA+AA GWAS meta-analyses (Figure 1A and Supplemental Figure S1). There were no NicW associations (P > 5×10−8) observed in the meta-analyzed EA or AA samples. In the meta-analyzed EA+AA sample, three closely mapped SNPs (rs246592, rs31746, rs31743) in an intergenic position within the PCDH-α, -β and -γ gene cluster on chromosome 5 (Figure 1B) were associated with NicW after a genomewide test correction (Pmeta < 5×10−8). No heterogeneity was detected in the meta-analysis (Cochran’s Q, p > 0.5, I2 =0). The statistical strength of the association was nearly indistinguishable among the three SNPs (P=2.3×10−8 – 4.8×10−8) and, as indicated by the 1000 Genome Project data,41 the pairwise correlation between all SNPs was high in populations of European (r2=1, D′=1) and African (r2>0.66, D′>0.98) ancestry. Rs31746 was directly genotyped by all arrays used in the study. The effect of rs31746, as indicated by the magnitude and direction of the odds ratio,
