A total of 12 364 participants of self-reported European ancestry, with complete smoking status (including cigarette consumption among current smokers), cotinine levels, and genotype data, were available across six studies (see Table 1). Participants were classified as never smokers (n = 4771), former smokers (n = 4661), and current smokers (n = 2932) based on their self-reported smoking behavior (see Table 2).
