Systematic review and meta-analysis of evidence on the efficacy of e-cigarette use for sustained smoking and nicotine cessation

ObjectiveTo systematically review and meta-analyse evidence regarding the efficacy of electronic nicotine delivery systems (ENDS) as smoking cessation aids. Data SourcesPubMed, Scopus, Web of Science, PsycINFO, MEDLINE and Cochrane Library were searched up to February-March 2020 (PROSPERO registration CRD42020170692). Study selectionPublished peer-reviewed randomised controlled trials (RCTs) of the efficacy of ENDS for sustained cessation of combustible tobacco smoking and/or nicotine use, compared with no intervention, placebo or nicotine replacement therapy (NRT) by intention-to-treat, with a minimum of four months follow-up. Data ExtractionData were extracted independently into a pre-specified template. Risk of bias was assessed with the Cochrane Collaborations tool and evidence quality rated using GRADE. Data SynthesisFrom 3,973 titles identified, nine RCTs were identified; 330 of 5,445 smokers randomised quit. Smoking cessation did notPublic health consequences differ significantly for randomisation to ENDS versus: no intervention (three studies, random-effects meta-analysis RR 1.95; 95%CI 0.90-4.22); placebo (three studies, 1.61; 0.93-2.78) or NRT (three studies; 1.25; 0.74-2.11). Fixed-effects sensitivity analyses showed significant results for ENDS vs NRT (1.43; 1.10-1.86). Smokers randomised to ENDS were substantially more likely than control to use nicotine at follow-up. Overall evidence quality was low. Considering only studies without potential competing interests further limited evidence but did not materially change conclusions. ConclusionsThere is insufficient evidence that ENDS are efficacious for smoking cessation compared to no intervention, placebo or NRT. Results are promising, particularly for therapeutic use, but vary according to analytic method. ENDS may lead to greater ongoing nicotine exposure than other smoking cessation methods. ImplicationsThis systematic review and meta-analysis consolidates current evidence on the efficacy of ENDS as an aid to sustained smoking and nicotine cessation and considers these findings in the context of potential competing interests. While findings are promising more research - preferably independent of industry funding - is needed to provide robust evidence of the efficacy of ENDS for smoking cessation. Future research should investigate nicotine cessation in addition to smoking cessation.