Associations of CYP2A6 genotype with smoking behaviors in southern China

Aims To investigate the association of CYP2A6 genetic polymorphisms with smoking-related phenotypes in Chinese smokers. Design Case-only genetic association study. Setting Southern China. Participants A total of 1328 Han Chinese smokers who participated in a community-based chronic disease screening project in Guangzhou and Zhuhai from 2006 to 2007. Measurements All participants answered a structured questionnaire about socio-demographic status and smoking behaviors and informative alleles were genotyped for the cytochrome P450 2A6 (CYP2A6) gene (CYP2A6 *4, *5, *7, *9 and *10). Findings The frequencies of CYP2A6 *4, *5, *7, *9 and *10 alleles were 8.5, 1.2, 6.3, 13.5 and 2.4%, which corresponded to 48.9, 15.4, 24.2 and 11.5% of participants being classified as normal, intermediate, slow and poor metabolizers, respectively. Multivariate analyses in male smokers demonstrated that compared with normal metabolizers, poor metabolizers reported smoking fewer cigarettes per day [adjusted odds ratio (OR) = 0.49; 95% confidence interval (CI): 0.32-0.76], started smoking regularly later in life (adjusted OR = 1.55; 95% CI: 1.06-2.26) and, among former smokers, reported smoking for a shorter duration prior to quitting (adjusted OR = 0.33; 95% CI: 0.12-0.94). However, poor metabolizers were less likely to quit smoking and remain abstinent than normal metabolizers (adjusted OR = 0.54; 95% CI: 0.34-0.86). Conclusions Reduced metabolism function of cytochrome P450 2A6 in smokers appears to be associated with fewer cigarettes smoked, later initiation of smoking regularly, shorter smoking duration and lower likelihood of smoking cessation.