Changes in E-Cigarette Use Behaviors and Dependence in Long-term E-Cigarette Users

Introduction: Little is known about the effects of long-term e-cigarette use, particularly the risks of relapse to cigarette smoking or increased dependence. Methods: In a 2012–2014 baseline online e-cigarette survey, 1,863 respondents consented to participate in future research. A follow-up online survey was conducted in 2017–2018 to assess changes in e-cigarette use behaviors and e-cigarette–related dependence. For both surveys, exclusive e-cigarette use was defined as only using e-cigarettes in the past 7 days, and poly use was defined as using both e-cigarettes and other tobacco or nicotine products in the past 7 days. The Penn State Electronic Cigarette Dependence Index (PSECDI) score was calculated for each study subject and was used to evaluate e-cigarette dependence. Paired t-tests or Pearson correlation coefficients were used to examine changes in e-cigarette use behaviors or PSECDI scores between baseline and follow-up. Baseline and follow-up survey data were analyzed in January 2019. Results: A total of 494 subjects provided complete data on both surveys. At baseline, 402 subjects (81.4%) were exclusive e-cigarette users, and 71 subjects (14.4%) were poly users. Among baseline exclusive e-cigarette users, the majority (88.3%) continued using e-cigarettes exclusively, but 37 users (9.2%) became poly users and 1 returned to cigarette smoking at follow-up. Among baseline poly users, 60.6% became exclusive e-cigarette users at follow-up. The mean PSECDI score remained similar over time (8.4 at baseline vs 8.3 at follow-up). Conclusions: Findings suggest that the risk of relapse to cigarette smoking is low, and e-cigarette-related dependence remains stable in long-term e-cigarette users.