Detailed information on the risk of bias in included studies

Authors (year) [ref.]Bias in the randomisation processDeviations from intended interventionsMissing outcome dataBias in measurement of the outcomeBias in selection of the reported result
Bonevski et al. (2021) [14]Low riskLow riskLow riskHigh risk: self-reported abstinence data without biochemical validationLow risk
Bullen et al. (2013) [17]Low riskSome 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 pharmaciesLow riskLow riskLow risk
Hajek et al. (2019) [18]Low riskLow riskLow riskLow riskLow risk
Lee et al. (2018) [20]Low riskLow riskLow riskLow riskLow risk

EC: e-cigarette; NRT: nicotine replacement therapy.