Use of moist smokeless tobacco (snus) and the risk of development of alcohol dependence: a cohort study in a middle-aged population in Sweden.

Background: Convincing evidence shows that smoking is associated with alcohol dependence (AD) and a positive correlation between snus and alcohol consumption was previously shown in cross-sectional studies. We performed a longitudinal evaluation of the risk of snus users to develop AD.

Methods: A cohort study in Västerbotten County, Sweden, linked individual data on socioeconomic situation and health survey data from 21,037 men and women (46.5% men). AD was defined by the CAGE questionnaire and evaluated at baseline 1991-1997 and again after 10 years. The risk of developing AD was assessed using logistic regression analysis and propensity score matching.

Results: 2370 men and 430 women used snus and were without AD at baseline. Over the 10-year period, 499 men and 257 women developed AD, among whom 191 and 26, respectively, were baseline snus users. The crude relative risks of AD for male and female snus users compared to non-users were 1.8 with 95% CI (1.5, 2.2) and 2.9 (2.0, 4.3), respectively. Adjusted logistic regression showed a positive dose-response relationship between snus use and risk of AD. Analyses involving propensity score matching revealed 33 and 17 new cases of AD in men and women, respectively, after 10 years given 1000 men and 1000 women without AD had been baseline snus users rather than non-users. Results for current, previous and never smokers were similar.

Conclusions: The use of snus is prospectively associated with an increased risk of AD with a dose-response relationship that is independent of smoking status.