Smoking and snus use onset: exploring the influence of snus debut age on the risk for smoking uptake with cross-sectional survey data.

INTRODUCTION Snus use has become increasingly prevalent among young people in Norway, while smoking has declined. Little is known about the transitions between snus and other tobacco products, particularly among younger users. A major concern involves the association between snus initiation and future smoking uptake. METHODS A total of 409 lifetime snus users who had started with snus before cigarettes or were never-smokers were selected from a national sample of participants in annually repeated cross-sectional surveys (2005-2011) of Norwegian men and women aged 15-74 years. About 30% of them were lifetime smokers, 84% were men, and the mean age was 29.4 years. Logistic regression was applied to investigate the association between age of snus uptake and the risk for becoming a smoker later on. RESULTS Respondents who started using snus before the age of 16 years had an odds ratio of 3.1 (confidence interval = 1.98-4.76) of being lifetime smokers compared with those who initiated snus later. The prevalence of current smoking among early snus initiators (22.9%) was comparable to that found among never-snus-users (29.6%). Among late snus initiators, current smoking prevalence was 5.9%. CONCLUSION In this study, snus debut age was an important factor for the association between snus use and smoking.