Evidence that an intervention weakens the relationship between adolescent electronic cigarette use and tobacco smoking: A 24 month prospective study

Background: The electronic cigarette (e-cigarette) use to subsequent smoking relationship in adolescents has received much attention. Whether an intervention to reduce smoking initiation attenuated this relationship was assessed. Method: Data were from 3994 adolescent never smokers (aged 13-14 years at baseline) as part of a cluster randomised controlled trial. Self-report measures of smoking, e-cigarette use and covariates were assessed and used to predict ever smoked cigarettes, any recent tobacco smoking, and regularly smoked cigarettes at 24-month follow-up. Results: Baseline ever use of e-cigarettes was associated with ever smoked cigarettes (OR= 4•03, 95%CI 3•33—4•88; controlling for covariates, OR=2•78, 95%CI 2•20—3•51), any recent tobacco smoking (OR=3•38, 95%CI 2•72—4•21; controlling for covariates, OR=2•17, 95%CI 1•76—2•69) and regularly smoked cigarettes (OR=3•60, 95%CI 2•35—5•51; controlling for covariates, OR=1•27, 95%CI 1•17—1•39) at follow-up. For ever smoked cigarettes only, the impact of e-cigarette use was attenuated in the intervention (OR=1•83) compared to control (OR=4•53) condition. For ever smoked cigarettes and any recent tobacco smoking, the impact of e-cigarette use was attenuated among those with friends who smoked (OR=2•05 [ever smoked]; 1•53 [any tobacco use]) compared to those without friends who smoked (OR=3•32 [ever smoked]; 2•17 [any tobacco use]). Conclusions: This is one of the first studies to show that e-cigarette use was robustly associated with measures of smoking over 24 months and the first to show an intervention to attenuate the relationship. Further research with a broader age-range of adolescents is required.