• Jamie Tam.
• Department of Health Policy and Management, Yale University School of Public Health, 60 College St., New Haven, CT 06510, United States. Electronic address: Jamie.Tam@yale.edu.
• Addict Behav. 2021 Jan 1; 112: 106636.

IntroductionYouth e-cigarette use has been rising, however U.S. prevalence data are generally reported without disaggregating by individuals' use of other tobacco products. It is not clear how the proportion of youth e-cigarette users naïve to all combustible tobacco is changing.MethodsAnnual prevalence estimates of ever and current (defined as past 30-day use) tobacco use prevalence by school type are reported using the 2014-2019 National Youth Tobacco Surveys (NYTS) with mutually exclusive categories of e-cigarette, smokeless tobacco, and/or combustible tobacco product use. T-tests were used to compare annual estimates with the preceding year. The annual percent change (APC) for each category from 2014 to 2018 were analyzed using JoinPoint regression. Data for 2019 were reported separately due to the change in survey format from paper to electronic.ResultsCurrent use of only e-cigarettes among HS students who never used combustible tobacco increased significantly from 2014 to 2018 (APC = +42.4%, 95% CI: 0.7, 101.3); by 2019, prevalence peaked at 9.2% (95% CI: 8.2, 10.2) among never combustible users and 8.3% (95% CI: 7.3, 9.3) among former combustible users. This coincided with significant declines in use of only combustible tobacco (APC = -14.5%, 95% CI: -18.3, -10.5).ConclusionsUse of only e-cigarettes among US youth with no history of combustible tobacco use has increased substantially over time, even as combustible tobacco use continues to decline. Of the 17.5% (95% CI: 15.7, 19.0) of HS students who currently used only e-cigarettes (but not other tobacco) in 2019, more than half have no history of combustible tobacco use.Copyright © 2020 Elsevier Ltd. All rights reserved.

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