Method: Data are drawn from the Community Youth Development Study (CYDS), a community-randomized trial of the Communities That Care prevention system that has followed 4,407 youth from 24 small communities in seven states (Colorado, Illinois, Kansas, Maine, Oregon, Utah, and Washington) since 2003. The current study uses data from the control group only (N = 2002). Youth have been surveyed annually at ages 10 to 16, and again at 18, 19, 21, and 23. Tobacco was measured at every age and e-cigarette use was measured at ages 21-23 (0 occasions to 40+ occasions in the past month and past year).
Results: Participants were classified as never users (never used cigarettes; 26%), regular users (used 100 cigarettes in their lifetime; 27%), or occasional users (< 100 cigarettes in their lifetime; N = 47%) by age 19. Preliminary findings suggest that at ages 21-23 76% of never users remained abstinent; 7% used only cigarettes, 9% only e-cigarettes, and 7% reported dual use. Regular users mostly reported dual use (68%) or cigarette only use (19%); 9% reported no nicotine use, and 4% only used only e-cigarettes. A majority of occasional users were smoke free by age 23 (53%), however, 23% engaged in dual use. In a logistic regression, e-cigarette use increase the odds of regular smoking at age 23 by 52% (p = .054) over and above age 19 and age 21 smoking. A propensity score analysis is planned to test whether e-cigarette use is a unique risk factor for tobacco use over and above other underlying risks.
Conclusions: E-cigarettes were rarely used alone, suggesting that their use is unlikely to decrease tobacco-related harms by steering tobacco smokers completely away from cigarettes. In addition, a nontrivial proportion of never users reported using e-cigarettes or dual use in the transition from age 19 to 21-23, increasing concerns over e-cigarettes as a gateway to cigarettes as a way to supply nicotine. Implications for e-cigarette control policies will be discussed.