Regular smokeless tobacco use is not a reliable predictor of smoking onset when psychosocial predictors are included in the model

Tomar (Nicotine & Tobacco Research, 5, 545-553) analyzed the CDC's Teenage Attitudes and Practices Survey (TAPS) and reported smokeless tobacco may act as a starter product for or gateway to cigarettes. Regular smokeless tobacco users at baseline were said to be 3.45 times more likely than never users of smokeless tobacco to become cigarette smokers after 4 years (95% CI = 1.84-6.47). However, this analysis did not take into account well-known psychosocial predictors of smoking initiation. We reanalyzed TAPS to assess whether including psychosocial predictors of smoking affected the smokeless tobacco gateway effect. Experimenting with smoking, OR = 2.09 (95% CI = 1.51-2.90); below average school performance, OR = 9.32 (95% CI = 4.18-20.77); household members smoking, OR = 1.49 (95% CI = 1.13-1.95); frequent depressive symptoms, OR = 2.19 (95% CI = 1.25-3.84); fighting, OR = 1.48 (95% CI = 1.08-2.03); and motorcycle riding, OR = 1.42 (95% CI = 1.06-1.91) diminished the effect of both regular, OR = 1.68 (95% CI = .83-3.41), and never regular smokeless tobacco use, OR = 1.41 (95% CI = .96-2.05), to be statistically unreliable. Analyzing results from a sample of true never smokers (never a single puff) showed a similar pattern of results. Our results indicate that complex multivariate models are needed to evaluate recruitment to smoking and single factors that are important in that process. Tomar's analysis should not be used as reliable evidence that smokeless tobacco may be a starter product for cigarettes.