Abstract
PURPOSE: The primary objectives were to (1) examine the initiation patterns of e-cigarette and cigarette smoking, (2) compare recent trends in initiation patterns for 2015, 2016, and 2017, (3) examine sociodemographic differences in initiation patterns over time and, (4) examine how initiation patterns are associated with cigarette-related perceptions, behaviors, and intentions. METHODS: Data were collected via self-administered questionnaires from 2015 to 2017 nationally representative samples of eighth-grade (modal ages 13-14 years) and 10th-grade (modal ages 15-16 years) students (N = 36,506) attending U.S. secondary public and private schools. RESULTS: Among lifetime e-cigarette or cigarette users (n = 9,858), initiating e-cigarettes only was the most common (47.45%). This was followed by cigarette before e-cigarette initiation (18.50%), which decreased in prevalence from 2015 to 2017. E-cigarette before cigarette initiation was the smallest group (6.89%) but increased from 2015 to 2017. E-cigarette before cigarette users were more likely to perceive cigarette use as risky (adjusted odds ratios [aOR]: 1.40; 95% CI: 1.11-1.77) but also more likely to currently smoke cigarettes (aOR:1.30; 95% CI: 1.03-1.63) compared with those who initiated cigarettes before e-cigarettes. Both cigarette only initiators (aOR: .52; 95% CI: .33-.80) and e-cigarette only initiators (aOR: .22; 95% CI: .07-.16) were less likely to report future intentions to smoke compared with those who initiated cigarettes before e-cigarettes. CONCLUSIONS: Initiation patterns related to e-cigarette and cigarette use among U.S. youth appears to be changing rapidly. Furthermore, patterns of initiation should be considered in future research as cigarette-related risk among different e-cigarette and cigarette use initiation patterns is heterogeneous.