Figures
- FIGURE 1
Flow diagram of the systematic review process. CENTRAL: Cochrane Central Register of Controlled Trials.
- FIGURE 2
Risk of bias for each study. Studies: Bonevski et al. (2021) [14], Bullen et al. (2013) [17], Hajek et al. (2019) [18], Lee et al. (2018) [20].
- FIGURE 3
Pooled results for nicotine abstinence, allocated product use and smoking cessation. Studies: Bonevski et al. (2021) [14], Bullen et al. (2013) [17], Hajek et al. (2019) [18], Lee et al. (2018) [20]. EC: e-cigarette; df: degree of freedom; M–H: Mantel–Haenszel; NRT: nicotine replacement therapy.
- FIGURE 4
Anticipated absolute effects. NRT: nicotine replacement therapy.
Tables
- TABLE 1
Characteristics of included studies
Authors (year) [ref.] Design Country Number of participants Eligibility criteria Participants’ characteristics Interventions Main outcome Bonevski et al. (2021) [14] RCT: two parallel groups New Zealand Total n=100: 50 EC, 50 NRT ≥18 years old; tobacco smokers and with capacity to provide informed consent 67% women, mean age 41 years, smoking 21 (mean) cpd Randomised to nicotine EC and NRT for 12 weeks Self-reported 6-week continuous abstinence at 12 weeks (not validated) Bullen et al. (2013) [17] RCT: three parallel groups Australia Total n=100: 289 nicotine EC, 295 patch, 73 non-nicotine EC (this group was not included in this review) ≥18 years old; smoked ≥10 cpd over past year, and wanted to stop smoking 62% women, mean age 42 years, smoking 18 (mean) cpd Randomised to nicotine EC, NRT, and non-nicotine EC for 12 weeks Continuous abstinence 6 months after quit day (biochemically validated) Hajek et al. (2019) [18] RCT: two parallel groups UK Total n=100: 439 EC, 447 NRT ≥18 years old; with no strong preference to EC and NRT, and were currently not using either type of product 48% women; median age 41 years, smoking 15 (median) cpd Randomised to nicotine EC and NRT (for at least 4 weeks and up to 3 months) Continuous abstinence 52 weeks after quit day (biochemically validated) Lee et al. (2018) [20] RCT: two parallel groups USA Total n=100: 20 EC, 30 NRT ≥18 years old; currently smoked ≥2 cpd and at least once in the last 7 days 10% women; mean age 54 years, smoking 14 (mean) cpd Randomised to nicotine EC (6-week supply) and NRT (5 weeks nicotine patch, 1 week placebo match) 7-day point prevalence abstinence at 6 months (biochemically validated) cpd: cigarettes per day; EC: e-cigarette; NRT: nicotine replacement therapy; RCT: randomised controlled trial.
- TABLE 2
Summary of findings: e-cigarettes versus nicotine replacement therapy (NRT) for nicotine abstinence, allocated product use and smoking cessation
Outcomes Relative effect (risk ratio (95% CI)) Number of participants (studies) Certainty of the evidence (GRADE) Comments Nicotine abstinence 0.50 (95% CI 0.32–0.77) 1568 (three RCTs) Moderate Downgraded one level due to imprecision (i.e. overall, a small number of events) Allocated product use among successful tobacco quitters at the end of the trial 8.94 (95% CI 3.98–20.07) 180 (three RCTs) Low Downgraded two levels due to imprecision (i.e. overall, a small number of events and too wide confidence intervals) Smoking cessation 1.58 (95% CI 1.20–2.08) 1598 (four RCTs) Moderate Downgraded one level due to imprecision (i.e. overall, a small number of events) Patient or population: adult current smokers; setting: Australia, New Zealand, UK and USA; intervention: e-cigarettes; comparison: NRT. GRADE: Grading of Recommendations Assessment, Development and Evaluation; RCT: randomised controlled trial. GRADE Working Group grades of evidence [10]: high – the authors have a lot of confidence that the true effect is similar to the estimated effect; moderate – the true effect is probably close to the estimated effect; low – the true effect might be markedly different from the estimated effect; very low – the true effect is probably markedly different from the estimated effect.
- TABLE 3
Detailed information on the risk of bias in included studies
Authors (year) [ref.] Bias in the randomisation process Deviations from intended interventions Missing outcome data Bias in measurement of the outcome Bias in selection of the reported result Bonevski et al. (2021) [14] Low risk Low risk Low risk High risk: self-reported abstinence data without biochemical validation Low risk Bullen et al. (2013) [17] Low risk Some concerns: adherence to study treatments was significantly higher in the EC group compared to the NRT group due to the trial context: i.e. participants in the EC group were provided with ECs and replacement cartridges, while those in the NRT group were provided with exchange cards redeemable for patches from community pharmacies Low risk Low risk Low risk Hajek et al. (2019) [18] Low risk Low risk Low risk Low risk Low risk Lee et al. (2018) [20] Low risk Low risk Low risk Low risk Low risk EC: e-cigarette; NRT: nicotine replacement therapy.
