LAUSR

Objective Using longitudinal data from two large-scale cohorts in the UK and USA, we examine whether e-cigarette use steers adolescent early smokers away from tobacco cigarettes (disruption hypothesis) or deepens early patterns of tobacco smoking (entrenchment hypothesis) in comparison with early smokers who do not use e-cigarettes. Methods Youth who smoked tobacco cigarettes by early adolescence (before age 15) were selected from the ongoing UK Millennium Cohort Study (n=1090) and the US Population Assessment of Tobacco and Health (n=803) study. In regression models, the focal predictor was lifetime use of an e-cigarette by early adolescence and the primary outcome was current tobacco use by late adolescence (before age 18). Logistic and multinomial models controlled for early adolescent risk factors and sociodemographic background, and were weighted for attrition and adjusted for complex survey designs. Results Among youth who were early cigarette smokers, 57% of UK and 58% of US youth also used e-cigarettes. The odds of later adolescent smoking among early smoking youth were significantly higher among e-cigarette users relative to those who had not used e-cigarettes (adjusted OR (AORUK)=1.45; AORUSA=2.19). In both samples, multinomial models indicated that early smoking youth who used e-cigarettes were more likely to be frequent smokers relative to not smoking (AORUK=2.01; AORUSA=5.11) and infrequent smoking (AORUK=1.67; AORUSA=2.11). Conclusions Despite national differences in e-cigarette regulation and marketing, there is evidence e-cigarette use among early adolescent smokers in the UK and USA leads to higher odds of any smoking and more frequent tobacco cigarette use later in adolescence.