Trajectories of smokeless tobacco use and of cigarette smoking in a cohort of Swedish adolescents: differences and implications.

Developmental trajectories of cigarette smoking have often been described, but there are no such analyses dealing with smokeless tobacco use. A semi-parametric group-based mixture modeling procedure was used to determine the development of smokeless tobacco (snus) use, as well as of cigarette smoking, over time in a cohort of 2,175 Swedish adolescents who were never-users of tobacco at the time of recruitment. An indicator of snus and of cigarette consumption in the previous year was used to model the development of the behavior between 11 and 18 years of age. For snus use three trajectories best described the cohort's experience, while four trajectories provided the best description of cigarette smoking in the cohort. For both tobacco types there were two escalation patterns and one sustained trial trajectory, while an extinction pattern was apparent for cigarette smoking only. Marked sex differences were found, since rapid escalation for snus use was found only among males while high consumption of cigarettes was observed only among females. Dual users (54.9% of all users) showed a trajectory of steeper and more prolonged increase of tobacco consumption than exclusive users of either snus or cigarettes. Several risk factors for tobacco use measured at baseline influenced individual probabilities of belonging to a particular trajectory. The developmental patterns of snus use and cigarette smoking showed high similarity, but they evolved differently in the two sexes. Dual users emerged as a high-risk group for tobacco dependence and tobacco-related harms.