RESUMEN
AIMS: To characterize smokeless tobacco initiation and persistence in relation to deployment, combat, occupation, smoking and mental health symptoms. DESIGN: Prospective cohort, utilizing self-reported survey data from the Millennium Cohort Study. SETTING: US military service members in all branches including active duty, reserve and National Guard. PARTICIPANTS: Population-based sample of 45,272 participants completing both baseline (July 2001-June 2003; n = 77,047) and follow-up (June 2004-January 2006; n = 55,021) questionnaires (follow-up response rate = 71.4%). MEASUREMENTS: Self-reported smokeless tobacco initiation and persistence. FINDINGS: Over the study period, 72.4% did not deploy, 13.7% deployed without combat exposures and 13.9% deployed with combat exposures, while 1.9% were smokeless tobacco initiators and 8.9% were persistent users. The odds of initiation were greater for deployers with combat exposure [odds ratio (OR), 1.76; 95% confidence interval (CI), 1.49-2.09], deployers without combat exposure (OR, 1.31; 95% CI, 1.07-1.60) and those who deployed multiple times (OR, 1.67; 95% CI, 1.31-2.14), as well as in smoking recidivists/initiators (OR, 4.65; 95% CI, 3.82-5.66) and those reporting post-traumatic stress disorder symptoms (OR, 1.54; CI, 1.15-2.07). A similar pattern for higher odds of persistent use was observed for deployment and combat exposure, but not for smoking and mental health symptoms. Military occupation was not significantly associated with initiation or persistence. CONCLUSIONS: Deployment and combat exposure in the US military are associated with increased risk of smokeless tobacco initiation and persistence while smoking and symptoms of post-traumatic stress disorder increase the odds for initiation. Research is needed on aspects of military service amenable to the reduction or prevention of tobacco consumption.