Introduction: Reports of the effectiveness of e-cigarettes (ECs) for smoking cessation vary across different studies making implementation recommendations hard to attain. We performed a systematic review and meta-analysis to assess the current evidence regarding effectiveness of ECs for smoking cessation.
Methods: PubMed, PsycInfo, and Embase databases were searched for randomized controlled trials comparing nicotine ECs with non-nicotine ECs or with established smoking cessation interventions (nicotine replacement therapy [NRT] and or counseling) published between 1 January 2014 and 27 June 2020. Data from eligible studies were extracted and used for random-effects meta-analyses (PROSPERO registration number: CRD42019141414).
Results: The search yielded 13 950 publications with 12 studies being identified as eligible for systematic review (N = 8362) and 9 studies for random-effects meta-analyses (range: 30-6006 participants). The proportion of smokers achieving abstinence was 1.71 (95 CI: 1.02-2.84) times higher in nicotine EC users compared with non-nicotine EC users. The proportion of abstinent smokers was 1.69 (95 CI: 1.25-2.27) times higher in EC users compared with participants receiving NRT. EC users showed a 2.04 (95 CI: 0.90-4.64) times higher proportion of abstinent smokers in comparison with participants solely receiving counseling.
Conclusions: Our results suggest that nicotine ECs may be more effective in smoking cessation when compared with placebo ECs or NRT. When compared with counseling alone, nicotine ECs are more effective short term, but its effectiveness appears to diminish with later follow-ups. Given the small number of studies, heterogeneous design, and the overall moderate to low quality of evidence, it is not possible to offer clear recommendations.
Implications: The results of this study do not allow for a conclusive argument. However, pooling current evidence points toward a potential for ECs as a smoking cessation tool. Though, given the overall quality of evidence, future studies should aim for more clarity in terms of interventions and larger study populations.
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