Is adolescent e-cigarette use associated with smoking in the United Kingdom?: A systematic review with meta-analysis

INTRODUCTION: Though smoking is a public health problem the use of e-cigarettes has been associated with a reduction in smoking in developed countries. However, public health experts have raised concerns about the association of e-cigarette use with an increase in traditional cigarette smoking in adolescents. Review-level evidence is generally supportive of this concern, but as it is mainly based on studies from the USA we investigated if e-cigarette use is associated with traditional cigarette smoking in adolescents (aged 10–19 years) in the UK. METHODS: We conducted a systematic review of empirical studies. Databases (PubMed, Medline via ProQuest, CINAHL and SCOPUS) were searched between January 2005 and May 2018 using search terms based on the concepts: adolescents, traditional cigarette smoking, e-cigarettes, and UK. Using pre-defined inclusion and exclusion criteria, a total of eight studies (involving 73076 adolescents) were included in this review. Three of the included studies were eligible to be combined in a meta-analysis. The CASP appraisal tool was used to assess study quality while risk of bias was assessed using ROBINS-I. RESULTS: Studies included in the meta-analysis showed that adolescents who use e-cigarettes are up to six times more likely to smoke traditional cigarettes. Furthermore, results showed that traditional cigarette smoking can also precede e-cigarette use in adolescents and there was increased likelihood of an increase in initial product use (e-cigarette or traditional cigarette) when the alternate product was initiated. CONCLUSIONS: Public health policy makers in the UK still need clear conclusions about the effects and safety of e-cigarettes.