To our knowledge this is the first GWAS of NMR reported to date. Despite a relatively small sample size (N = 1518), we detected a multitude of genome-wide significant signals on 19q13.2, highlighting the power of informative biomarkers in GWAS and demonstrating the power of Finnish population samples to identify novel genes even with a modest sample size. Our genetic and epigenetic analyses enclosed several genes as potential players in regulating NMR. Four members of the cytochrome P450 gene family (CYP2A6, CYP2B6, CYP2A7, and CYP2F1) were highlighted, although only CYP2A6 encompassed independent signals. Three additional highlighted genes (DLL3, NUMBL, and EGLN2) are functionally linked according to the GeneMania database (http://www.genemania.org/), suggesting that an interplay between these genes may influence NMR. Future studies are needed to elucidate the potential role of these genes in NMR. The detected novel CYP2A6 variants explain a strikingly large fraction of variance (up to 31%) in NMR in the current sample, suggesting that they tag both known and unidentified functional variants. The population-attributable effect of the detected independent variants is thus far greater than that of
