Frequency of use and smoking status of US adolescent e-cigarette users: a secondary analysis of the 2015 National Youth Tobacco Survey

Introduction: E-cigarette use by adolescents is an important issue for public health. This study analyzed the frequency of e-cigarette use and its association with smoking status among U.S. adolescents. Methods: The National Youth Tobacco Survey 2015 was analyzed in 2017, focusing on frequency of past 30-day e-cigarette use according to smoking status of participants. Smoking status was classified as never smoker, ever/not a past 30-day smoker, and past 30-day smoker. Infrequent and frequent smoking and e-cigarette use was defined as use for o20 and ≥20 of the past 30 days, respectively. Results: Past 30-day e-cigarette use was reported by 54.5% (95% CI¼47.8%, 61.0%) of past 30-day smokers, 26.5% (95% CI¼23.2%, 30.1%) of ever/not past 30-day smokers, and 4.6% (95% CI¼4.0%, 5.2%) of never smokers (po0.001). No past 30-day e-cigarette use was reported by 94.5% and frequent e-cigarette use by 0.3% of never smokers. Past 30-day e-cigarette use was reported by 50.4% (95% CI¼43.6%, 57.3%) of infrequent and 64.7% (95% CI¼54.4%, 73.8%) of frequent past 30-day smokers (po0.001). E-cigarette use frequency correlated with both smoking status and tobacco cigarette consumption (ρ¼0.42, po0.001 and ρ¼0.40, po0.001, respectively). Past 30-day smokers were more likely to report past 30-day e-cigarette use (OR¼11.42, 95% CI¼9.06, 14.40) compared with adolescents reporting no past 30-day smoking. Conclusions: E-cigarette use is more prevalent among ever and past 30-day smoking adolescents compared with never smoking adolescents. Frequent e-cigarette use is rare among never smoking adolescents.