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Systematic Review
Electronic cigarettes (EC) are handheld electronic vaping devices that produce an aerosol by heating a liquid. People who smoke, healthcare providers, and regulators want to know if EC can help people quit smoking, and if they are safe to use for this purpose. This review update was conducted as part of a living systematic review.
The authors included 104 completed studies (14 new to this update), representing 30,366 participants, of which 61 were randomised controlled trials (RCTs). The authors rated 11 included studies as being at low risk of bias, 70 at high risk (including all non‐randomised studies), and the remainder at unclear risk overall.
Nicotine EC result in increased quit rates compared to nicotine replacement therapy (NRT) (high‐certainty evidence) (RR 1.55, 95% CI 1.28 to 1.88; I² = 0%; 9 studies, 2703 participants). In absolute terms, this might translate to an additional three quitters per 100 (95% CI 2 to 5 more). The rate of occurrence of AEs is probably similar between groups (moderate‐certainty evidence (limited by imprecision)) (RR 1.00, 95% CI 0.73 to 1.37; I² = 58%; 7 studies, 2241 participants). SAEs were rare, and there is insufficient evidence to determine whether rates differ between groups due to very serious imprecision (RR 1.22, 95% CI 0.73 to 2.03; I² = 30%; 8 studies, 2950 participants; low‐certainty evidence).
Nicotine EC probably result in increased quit rates compared to non‐nicotine EC (moderate‐certainty evidence, limited by imprecision) (RR 1.34, 95% CI 1.06 to 1.70; I² = 0%; 7 studies, 1918 participants). In absolute terms, this might lead to an additional two quitters per 100 (95% CI 0 to 4 more). There is probably little to no difference in the rate of AEs between these groups (moderate‐certainty evidence) (RR 1.01, 95% CI 0.95 to 1.08; I² = 0%; 5 studies, 840 participants). There is insufficient evidence to determine whether rates of SAEs differ between groups, due to very serious imprecision (RR 0.98, 95% CI 0.55 to 1.73; I² = 0%; 10 studies, 1717 participants; low‐certainty evidence).
Compared to behavioural support only or no support, quit rates may be higher for participants randomised to nicotine EC (low‐certainty evidence due to risk of bias) (RR 1.78, 95% CI 1.42 to 2.25; I² = 13%; 11 studies, 6819 participants). In absolute terms, this represents an additional three quitters per 100 (95% CI 2 to 5 more). There was some evidence that (non‐serious) AEs may be more common in people randomised to nicotine EC (RR 1.22, 95% CI 0.96 to 1.55; I² = 66%; 8 studies, 2485 participants; very low‐certainty evidence) but the evidence is uncertain and, again, there was insufficient evidence to determine whether rates of SAEs differed between groups (RR 0.93, 95% CI 0.67 to 1.29; I² = 0%; 15 studies, 4716 participants; very low‐certainty evidence).
There is high‐certainty evidence that nicotine EC increase quit rates compared to NRT, and moderate‐certainty evidence that they probably increase quit rates compared to EC without nicotine. Evidence comparing nicotine EC with behavioural support or no support also suggests benefit, but is less certain due to risk of bias inherent in the study designs.
The main limitation of the evidence base remains imprecision for some comparisons and for safety outcomes due to the relatively small number of RCTs contributing, often with low event rates. Further RCTs are underway. To ensure the review continues to provide up‐to‐date information to decision‐makers, this is a living systematic review.