OBJECTIVES: Despite the aggressive marketing of electronic nicotine device systems (ENDS) as smoking cessation tools, the evidence of their effectiveness is mixed. We conducted a systematic review of randomised controlled trials to determine the effect of ENDS on cigarette smoking cessation, as compared with other types of nicotine replacement therapies (NRT).

DESIGN: Systematic review and meta-analysis using the Grading of Recommendations Assessment, Development and Evaluation approach.

SEARCH: MEDLINE, Embase, the CENTRAL Trials Registry of the Cochrane Collaboration using the Ovid interface, ClinicalTrials.gov and the WHO International Clinical Trials Registry Platform trials registries were searched through 17 June 2020. Search criteria involved randomised controlled trials in which any type of ENDS was compared with any type of NRT, in traditional cigarette users.

DATA EXTRACTION AND SYNTHESIS: The primary outcome was smoking cessation, defined as abstinence from traditional cigarette smoking for any time period, as reported in each included study, regardless of whether abstinence is self-reported or biochemically validated. Secondary outcomes included smoking reduction, harms, withdrawal and acceptance of therapy. A random-effect model was used, and data were pooled in meta-analyses where appropriate.

RESULTS: Six studies were retained from 270. Most outcomes were judged to be at high risk of bias. The overall quality of evidence was graded as 'low' or 'very low'. Pooled results showed no difference in smoking cessation (rate ratio (RR) 1.42, 95% CI 0.97 to 2.09), proportion of participants reducing smoking consumption (RR 1.25, 95% CI 0.79 to 1.98), mean reduction in cigarettes smoked per day (mean difference 1.11, 95% CI -0.41 to 2.63), or harms (RR 0.96, 95% CI 0.76 to 1.20), between groups.

CONCLUSION: We found no difference in smoking cessation, harms and smoking reduction between e-cigarette and NRT users. However, the quality of the evidence was low. Further research is needed before widespread recommendations are made with regard to the use of ENDS.