Association Between Electronic Nicotine Delivery Systems and Electronic Non-Nicotine Delivery Systems With Initiation of Tobacco Use in Individuals Aged < 20 Years - A Systematic Review and Meta-Analysis

Background: This systematic review described the association between electronic nicotine delivery systems and electronic non-nicotine delivery systems (ENDS/ENNDS) use among non-smoking children and adolescents aged <20 years with subsequent tobacco use. Methods: We searched five electronic databases and the grey literature up to September 2020. Prospective longitudinal studies that described the association between ENDS/ENNDS use, and subsequent tobacco use in those aged < 20 years who were non-smokers at baseline were included. The Joanna Briggs Institute Critical Appraisal Checklist was used to assess risk of bias. Data were extracted by two reviewers and pooled using a random-effects meta-analysis. We generated unadjusted and adjusted risk ratios (ARRs) describing associations between ENDS/ENNDS and tobacco use. Findings: A total of 36 publications met the eligibility criteria, of which 25 were included in the narrative review (23 in the meta-analysis) after exclusion of overlapping studies. Sixteen studies had high to moderate risk of bias. Ever users of ENDS/ENNDS had over two times the risk of ever cigarette use (ARR 3·01 (95% CI: 2·37, 3·82; p<0·001, I2: 82·3%), and current cigarette use (ARR 2·56 (95% CI: 1·61, 4·07; p<0·001, I2: 77·3%) at follow up. Among current ENDS/ENNDS users, there was a significant association with ever (ARR 2·63 (95% CI: 1·94, 3·57; p<0·001, I2: 21·2%)), but not current cigarette use (ARR 1·88 (95% CI: 0·34, 10·30; p=0·47, I2: 0%)). For other tobacco use, ARR ranged between 1·55 (95% CI 1·07, 2·23) and 8·32 (95% CI: 1·20, 57·04) for waterpipe and pipes, respectively. Additionally, two studies examined the use of ENNDS specifically and found a pooled adjusted RR of 2·56 (95% CI: 0·47, 13·94, p=0.035). Interpretation: There is a need for policies that regulate the availability, accessibility, and marketing of ENDS/ENNDS to children and adolescents to curb use among this age group. Funding Statement: World Health Organization from a grant by the Bill and Melinda Gates Foundation Declaration of Interests: All authors declare no conflict of interests.