Association of CYP2A6 gene polymorphisms with cigarette consumption: a meta-analysis

Aims: A meta-analysis was performed to assess the association of hepatic cytochrome P450 2A6 (CYP2A6) gene polymorphisms with cigarette consumption.

Methods: A comprehensive search was conducted to identify the studies of the above-mentioned association. The fixed effect model (FEM) or random effect model (REM) was selected based on the homogeneity test among studies. Heterogeneity among studies was evaluated using the I(2). Meta-regression and the "leave one out" sensitive analysis were utilized to explore potential sources of heterogeneity. Publication bias was estimated by Harbord test. The effect of CYP2A6 gene polymorphisms on cigarette consumption was presented as standardized mean difference (SMD) with 95% confidence intervals (CI).

Results: After excluding one article that was the key contributor to between-study heterogeneity, there was a significant difference of cigarettes per day in groups of normal vs. reduced metabolizers of CYP2A6 gene (FEM: SMD = 0.134, 95%CI: 0.049-0.219). There was also a significant difference of age of smoking initiation between normal and intermediate metabolizers of CYP2A6 gene (FEM: SMD = 0.216, 95%CI: 0.056-0.377). No significant difference of tobacco dependence between normal and reduced metabolizers of CYP2A6 gene was found (FEM: SMD = 0.185, 95%CI = -0.001 to 0.371).

Conclusion: This meta-analysis suggests that CYP2A6 gene polymorphism is associated with daily cigarette consumption. Individuals with intermediate nicotine metabolism might also initiate smoking later than normal metabolism.