Efficacy of electronic cigarettes for tobacco smoking cessation: An adapted systematic review

Abstract

Abstract Background Worldwide smoking remains the leading cause of preventable morbidity and mortality. Electronic cigarettes (ECs) are increasingly used by tobacco smokers as an aid to smoking cessation; however, their efficacy remains uncertain. Methods Electronic databases, clinical trial registries and grey literature sources were searched. The aim was to examine randomised controlled trials or prospective cohort studies, published since the 2016 Cochrane review on this topic, that assessed the efficacy of ECs in achieving smoking cessation among current smokers. Results Two RCTs and five cohort studies, including a total of 16,460 participants, were eligible for inclusion. One RCT found sustained 1-year abstinence of 18.0% in the EC group versus 9.9% in the nicotine replacement therapy group (RR: 1.83; 95% CI 1.30 to 2.58; P < 0.001). The second RCT did not find a statistically significant difference in abstinence rates between EC users and non-users (RR 0.71). Of the five included cohort studies, four reported statistically significant RRs. Two found a positive association (RRs of 1.45 and 1.84) between EC use and smoking cessation but two studies showed EC use was associated with reduced smoking cessation (RRs of 0.25 and 0.35). Due to significant heterogeneity between the studies the data were deemed unsuitable for pooling into a meta-analysis. All trials assessing smoking reduction reported higher rates of reduction among EC users. No serious adverse events were reported with EC use. Follow-up periods of included trials ranged from one to four years, with an average of 1.6 years. Conclusions There is limited, low-quality evidence that ECs are an effective intervention for smoking cessation and smoking reduction. The overall quality of evidence is low as it is based on a small number of studies with inconsistent and imprecise results. Due to the short follow-up periods of the included trials, the long-term safety of ECs is unclear from this review. Key messages Limited evidence that electronic cigarettes are an effective smoking cessation intervention. Further well-designed randomised controlled trials are required to investigate the efficacy of ECs for smoking cessation.