Abstract
Aim: This systematic review of longitudinal cohort studies aimed to explore whether electronic cigarette (e-cigarette) use by adolescents, in Europe and North America, who had never smoked conventional tobacco cigarettes (tobacco cigarettes) at baseline was associated with subsequent initiation of tobacco cigarette smoking. Methods: A key word search identified peer-reviewed literature published between 1 January 2005 and 2 October 2019 from seven bibliographic databases and one search engine. Using a predefined inclusion/exclusion criteria two authors independently screened abstracts, and subsequently, full text papers. Eligible papers were quality assessed and scored by two authors. Included papers had data on population characteristics, exposure and outcome measures extracted into an adapted Cochrane Data Extraction Form. Statistical analysis was preceded by a feasibility assessment, and included a pairwise random effects meta-analysis, and sensitivity and subgroup analyses. Findings: From an initial 6,619 studies (6,510 papers from the initial searches, plus 109 papers from supplemental searches), 14 unique studies in 21 papers were identified. Nine of the 14 unique longitudinal studies with follow-up periods between 4 and 24 months were eligible for inclusion in a meta-analysis of the association between ever use of e-cigarettes and subsequent initiation of tobacco cigarette use. Based on primary study adjusted odds ratios, our meta-analysis calculated a 4.06 (95%confidence interval (CI): 3.00-5.48) times higher odds of initiating tobacco cigarette smoking for those who had ever used e-cigarettes at baseline, although the odds ratio was reduced slightly (to 3.71 times odds, 95%CI: 2.83-4. 86) when only the four high-quality studies were included. The initial meta-analysis model had a moderate to high statistical heterogeneity, sensitivity analysis restricted to high-quality studies had a low to moderate statistical heterogeneity. Conclusion: The systematic review found that e-cigarette use was associated with initiation of tobacco cigarette smoking among adolescents in Europe and North America, identifying a potentially serious public health harm. Given the widespread availability and use of e-cigarettes, this study further supports urgent action by policymakers to prevent their use by adolescents to reduce direct harms in this vulnerable population group as well as to protect gains in reducing tobacco cigarette initiation.
Electronic cigarette use and smoking cessation in cohort studies and randomized trials: A systematic review and meta-analysis
