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.