Table 1.

Characteristics of included studies

Characteristics of RCTs measuring smoking cessation at 6 months or later
Author and year of publication	Design	Country	No of participants	Main eligibility criteria	Intervention	Comparator	Main outcome of interest
Bullen, 201318	3 group, parallel, single centre	Australia	657 total, 584 included in this review (2 of 3 groups)	>18 years, smoked >10 cigarettes per day in the past year, motivated to quit	First-generation e-cigarette × 12 weeks	Nicotine patch x 12 weeks	Continuous abstinence 6 months after quit day
Hajek 20194	2 group, parallel, multicentre	UK	884	Adults with no strong preference towards e-cigarette or NRT	Any type of e-cigarette	Any nicotine-replacement therapy	Continuous abstinence 52 weeks after quit day
Lee, 201921	2 group, parallel, single centre	Republic of Korea	150	>18 years, smoked >10 cigarettes per day in the past year, motivated to quit	e-cigarette × 24 weeks	Nicotine gum × 24 weeks	Continuous abstinence 24 weeks after quit day
Lee, 201921	2 group, parallel, single centre	USA	30	Adults, smoked >2 cigarettes per day in the past year, smoked at least once in last 7 days	e-cigarette × 6 weeks	Nicotine patch × 5 weeks, then placebo patch × 1 week	7-day point prevalence abstinence at 6 months
Characteristics of RCT measuring smoking cessation earlier than 6 months
Hatsukami, 201920	4 group, parallel, multicentre	USA	264 total, 152 included in this review (2 of 4 groups)	>18 years, smoked >5 cigarettes per day	e-cigarettes	Nicotine gum or nicotine lozenge	7-day point prevalence abstinence at 8 months
Characteristics of RCT measuring other outcomes
Eisenhofer, 201519	2-group, parallel, single centre	USA	11	Veterans who met criteria for tobacco disorder	e-cigarettes × 3 weeks	Nicotine patch × 3 weeks	Reduction in no of cigarettes smoked per day at 3 weeks

NRT, nicotine replacement therapies; RCT, randomised controlled trial.