SNPs in the nAChR cluster with cigarettes smoked per day in current smokers, and packyears in ever smokers at the last survey.

B = regression coefficient derived from linear regression model, adjusted for age and gender;*only current smokers at the last survey;**ever smokers are current smokers and ex-smokers together.a = heterozygote vs. wild-type.b = homozygote variant vs. wild-type.