BACKGROUND: People who smoke conventional cigarettes are increasingly turning to electronic cigarettes (e-cigarettes) as a pathway to quitting. However, the efficacy and safety of e-cigarettes for smoking cessation remains controversial.

METHODS: We conducted a systematic review and meta-analysis of randomized controlled trials (RCTs), identified through a systematic search of the MEDLINE, EMBASE, and Cochrane CENTRAL databases. Inclusion was restricted to RCTs with a follow-up duration ≥6 months. The primary endpoint was the most rigorous criterion of biochemically validated abstinence at maximum follow-up, and the primary comparison was nicotine e-cigarettes versus any conventional (ie, non-e-cigarette) smoking cessation therapy. The Cochrane Risk of Bias Tool was used to assess bias. Count data were pooled across trials using random-effects models with inverse variance weighting to estimate relative risks (RRs) and corresponding 95% confidence intervals (CIs). We registered the study protocol with the Open Science Framework Registries (osf.io/26fkq).

RESULTS: A total of 5 RCTs (n = 3253) were included. Compared with conventional smoking cessation therapies, the use of nicotine e-cigarettes was associated with an increase in abstinence, defined by the most rigorous criterion of abstinence reported (RR 1.77; 95% CI, 1.29-2.44). Nicotine e-cigarettes also increased abstinence (defined by the most rigorous criterion) compared with non-nicotine e-cigarettes (RR 1.56; 95% CI, 1.13-2.15). The incidence of death or serious adverse events was low across all trials at maximum follow-up.

CONCLUSIONS: Among individuals attempting to quit smoking, nicotine e-cigarettes are more efficacious than conventional nicotine replacement or behavioral smoking cessation therapies, and may prove beneficial in reducing smoking-related health risks.