Associations between CYP2A6 genotype and smoking status in adults have been evaluated in several case-control studies (Munafo et al., 2004). Specifically, reduced or null activity CYP2A6 alleles are significantly more prevalent among nonsmokers, as compared to smokers of Caucasian (Malaiyandi et al., 2005; Pianezza et al., 1998), Japanese (Iwahashi et al., 2004), and African-American descent (Mwenifumbo et al., 2007). Among individuals who smoke, those with reduced activity or null variants of CYP2A6 tend to be lighter smokers (Fujieda et al., 2004; Malaiyandi et al., 2006b; Malaiyandi et al., 2005; Minematsu et al., 2006; Mwenifumbo et al., 2007; Rao et al., 2000; Schoedel et al., 2004; Tyndale et al., 1999) and are also less dependent on nicotine (Kubota et al., 2006; Malaiyandi et al., 2006b). Further, decreased cigarette consumption in slower metabolizers is associated with lower levels of plasma cotinine and breath carbon monoxide (CO) readings (Rao et al., 2000). These differences may be due to smoking fewer cigarettes, as well as to the decreased puff volume observed during smoking in slow metabolizers, compared to smokers who carry wild-type alleles (Strasser et al., 2007).
