DRD2/ANKK1 TaqI polymorphism and smoking behavior of Egyptian male cigarette smokers

Little is known about the genetic contribution to cigarette smoking and nicotine addiction in Egypt. The dopamine D2 receptor gene contains a TaqI repeat fragment length polymorphism creating two alleles with functional significance, DRD2* A1 and DRD2* A2. We investigated the relationship between these alleles and tobacco use in a study of 389 Egyptian male current smokers (mean age=40 years; SD=12). Participants were interviewed in 2004 on their smoking behaviors and quit attempts, and were given the Fagerstrom m Test for Nicotine Dependence (FTND). Blood samples were obtained and genotyped for DRD2 A1 and A2 alleles. The frequencies of A1/ A2, A1/ A2, and A2/ A2 genotypes were 6%, 29%, and 65%, respectively. We found no statistically significant association between genotype and age at onset of smoking, years of smoking, FTND score, or average number of cigarettes smoked per day. DRD2 genotype was associated with the number of cigarettes smoked in the past 48 hr (42.2 in A1 carriers vs. 37.6 in A2, p=.03), the previous quit duration (28% in A1 vs. 40% in A2 quit for more than 1 month, p=.05), and the depth of inhalation (82% in A1 vs. 72% in A2 inhaled the smoke deeply, p=.03). Logistic regression analysis including DRD2 genotype, FTND score, age at smoking initiation, marital status, and education as predictors showed that maximum duration of quit time was associated with FTND score (p=.003), DRD2 genotype (p=.01), marital status (p=.03), and age at smoking initiation (p=.04). These findings suggest a modest association between DRD2 genotype and quitting behavior in male cigarette smokers in Egypt.