Background:
E-cigarette ever-use and current-use among teenagers has been increasing worldwide, including in Ireland. Boys are widely observed to have higher prevalence compared with girls.

Objectives:
We set out to identify trends in e-cigarette ever-use and current use between 2015 and 2019, particularly in relation to gender differences.

Methods:
Data drawn from two Irish waves of the European School Survey Project on Alcohol and other Drugs (ESPAD) yielded a total valid sample of 3,421 16-year-olds from a stratified random sample of schools (n=50), comprising 1,472 students (born in 1999) in 2015, and 1,949 students (born in 2003) in 2019. Trends in e-cigarette ever- and current use were examined using a multivariable logistic regression model using e-cigarette ever- (Table 1) and current (Table 2) use as the dependent variable, for all and by gender.

Results:
E-cigarette ever-use increased from 23% to 39% and current-use from 10% to 18%, (2015 vs 2019 respectively). The rate of increase is significantly greater for girls AOR 2.67 (C.I. 2.02, 3.54) vs 2.04 (C.I. 1.55, 2.68). Smoking and e-cigarette use are linked and never-smokers becoming e-cigarette ever-users has risen from 33% to 67%. Peer smoking is also significantly associated with e-cigarette ever- and current-use, and the association is particularly strong for boys if “Most/All friends smoke” AOR 5.90 (C.I. 3.31, 10.52) vs 3.50 (C.I. 1.79, 6.84) for girls. Less parental monitoring is associated with greater e-cigarette use, more so for boys AOR 5.50 (C.I. 2.85, 10.61) vs 5.31 (C.I. 3.01, 9.37) for girls.

Conclusions:
Boys are currently at greater risk of e-cigarette use but girls are increasingly at risk. Peer influences and less parental monitoring are significant risk factors for use, operating differently for girls and boys, and providing potential mechanisms for interventions to prevent an increasing risk of nicotine addiction.