E-Cigarette Use and Combustible Cigarette Smoking Initiation among Youth: Accounting for Time-Varying Exposure and Time-Dependent Confounding
Menée aux Etats-Unis à partir de données d'enquêtes réalisées sur la période 2013-2019 auprès de 9 584 adolescents (âge : 12-17 ans), cette étude analyse l'association entre le vapotage et la consommation de cigarettes
Background: Youth e-cigarette use is associated with initiation of combustible cigarette smoking, but prior studies have rarely accounted for time-varying measures of e-cigarette exposure or time-dependent confounding of e-cigarette use and smoking initiation. Methods: Using five waves of the Population Assessment of Tobacco and Health (2013-2019), we estimated marginal structural models with inverse probability of treatment and censoring weights to examine the association between time-varying e-cigarette initiation and subsequent cigarette smoking initiation among e-cigarette- and cigarette-naïve youth (12-17y) at baseline. Time-dependent confounders used as predictors in inverse probability weights included tobacco-related attitudes or beliefs, mental health symptoms, substance use, and tobacco-marketing exposure. Results: Among 9,584 youth at baseline, those who initiated e-cigarettes were 2.4 times as likely to subsequently initiate cigarette smoking as youth who did not initiate e-cigarettes (risk ratio [RR]=2.4, 95% CI: 2.2-2.7), after accounting for time-dependent confounding and selection bias. Among youth who initiated e-cigarettes, more frequent vaping was associated with greater risk of smoking initiation (RR ≥3 days/month=1.8, 95% CI: 1.4-2.2; 1-2 days/month=1.2, 95% CI: 0.93-1.6 vs. 0 days/month). Weighted marginal structural model estimates were moderately attenuated compared to unweighted estimates adjusted for baseline-only confounders. At the United States population-level, we estimated over half a million youth initiated cigarette smoking because of prior e-cigarette use over follow-up. Conclusions: The association between youth vaping and combustible cigarette smoking persisted after accounting for time-dependent confounding. We estimate that e-cigarette use accounts for a considerable share of cigarette initiation among US youth.