OBJECTIVEA Meta-analysis was performed to assess the association of defective hepatic cytochrome P450 2A6 (CYP2A6) gene with smoking behaviors.

METHODSAll eligible studies published up to 2014 were searched out from PubMed, China National Knowledge Internet (CNKI), ISI Web of knowledge (ISI), vip citation databases (VIP), Chinese BioMedical Literature (CBM) and Elsevier Science Direct, searching words were "smok*","nicotine dependence","CYP2A6","cytochrome P450 2A6","polymorphism","mut*"and"varia*", while 436 articles were concluded. Meta-analysis was performed using Statal 3.1.

RESULTSA total of ten studies were finally included. We didn't find a significant effect of defective CYP2A6 gene on smoking initiation (fixed effect model (FEM): OR = 0.90, 95%CI: 0.78-1.03, I(2) = 25.8%), smoking persistence (random effect model (REM): OR = 0.85, 95%CI: 0.59-1.23, I(2) = 66.3%) and smoking cessation (REM: OR = 0.89, 95%CI: 0.57-1.40, I(2) = 67.1%). But it showed a significant protective effect of CYP2A6*4 on smoking initiation (FEM: OR = 0.78, 95%CI: 0.61-0.99, I(2) = 28.2%), smoking persistence (FEM: OR = 0.53, 95%CI: 0.36-0.77, I(2) = 41.0%) and smoking cessation (REM: OR = 0.49, 95%CI: 0.31-0.80, I(2) = 0.0%).

CONCLUSIONSThis Meta-analysis suggested that there was not a protective effect of defective CYP2A6 gene against smoking behaviors. But smokers with whole CYP2A6 gene deletion would be less likely to start smoking, less smoking persistence and more likely to quit smoking successful than smokers with wild CYP2A6 gene.

Aryl Hydrocarbon Hydroxylases ; Asian Continental Ancestry Group ; China ; Cytochrome P-450 CYP2A6 ; Gene Deletion ; Humans ; Polymorphism, Genetic ; Protective Factors ; Smoking ; Smoking Cessation ; Tobacco Use Disorder

OBJECTIVETo study the association between reasons for smoking and results related to successful smoking cessation.

METHODSA community-based case-control study was conducted with 642 male adults recognized as successful spontaneous smoking quitters being the subject cases while another 700 male adults who had failed to quit smoking were served as the controls. Russell Reason for Smoking Questionnaire (RRSQ) was used to investigate the reasons for smoking. Dominance logistic regression was performed to determine the relative importance of reasons for starting smoking and the endpoint of successful quit smoking.

RESULTSAfter adjusting the potential confounders of age, age of smoking initiation, marital status, profession, and education, the adjusted means of sedative and stimulation of RRSQ in the successful quitters were significant lower than that in the failed quitters. Results from the dominance logistic regression showed that the first two important factors for smoking cessation were sedative and stimulation of RRSQ, followed by psychological image, automatic, hand-mouth activity, indulgence, and addiction.

CONCLUSIONThis study demonstrated that factors as dependence-addiction showed more important impacts than the social-psychological ones on the endpoint of successful smoking cessation.

Adult ; Behavior, Addictive ; Case-Control Studies ; Humans ; Male ; Smoking ; psychology ; Smoking Cessation ; statistics & numerical data ; Smoking Prevention ; Surveys and Questionnaires