Czoli 2019.

Study characteristics
Methods	Design: Nonblinded within‐participants cross‐over Recruitment: advertisements placed in newspapers, online, and in local vape shops, and received CAD 295 for participating in the study Setting: Kitchener−Waterloo and Toronto, Ontario, Canada Study start date: September 2015. Study end date: NR
Participants	Total N: 48 29.2% female; mean age 35.9 (SD 11.7); mean cpd NR; dual EC users at baseline; not motivated to quit Inclusion criteria: > 18 Dual user s of tobacco cigarettes and e‐cigarettes. Dual users were identified as current daily tobacco cigarette smokers (had smoked ≥ 100 cigarettes in their lifetime, and smoked ≥ 5 cigarettes/day) and current daily e‐cigarette users (had used an e‐cigarette at least once a day for each of the past 7 days) Exclusion criteria: Serious intentions to quit smoking in the next 6 months use of other tobacco products in the past 7 days use of nicotine replacement therapy in the past 7 days use of any smoking cessation medications in the past 7 days participation in individual or group counseling programs for smoking cessation in the past 7 days experience of serious cardiac health issues experience of a heart attack or stroke within the last 3 months experience of cancer within the last year experience of asthma, chronic obstructive pulmonary disease, a seizure disorder, or any life‐threatening medical conditions with a prognosis of less than a year a history of psychosis, schizophrenia, bipolar disorder, or suicidal thoughts
Interventions	EC: own choice (mainly tank) 3 consecutive 7‐day periods in which the use of tobacco cigarettes and e‐cigarettes was experimentally manipulated 4 study conditions: Dual use (e‐cigarette and tobacco cigarette); Tobacco cigarette; E‐cigarette; No product use Virtually all dual users reported using tank systems (92%) and e‐cigarettes with nicotine (94%) To control for order effects, participants were randomly assigned to 1 of 2 condition orders, A or B Following the baseline condition of dual use: Group A participants switched to E‐cigarette use, then to Tobacco cigarette use, and finally to No product use Group B participants switched to Tobacco cigarette use, then to E‐cigarette use, and finally to No product use
Outcomes	Baseline (visit 1) and after each of the 7‐day periods (visit 2 (week 1), visit 3 (week 2), visit 4 (week 3)) Carbon monoxide Urinary concentration of cotinine Urinary concentrations of 1‐hydroxypyrene (1‐HOP) and 4‐(methylnitrosamino)‐1‐(3‐pyridyl)‐1‐butanol (NNAL)
Study funding	This research was supported by an Ontario Ministry of Health and LongTerm Care Health System Research Fund grant (#06697 awarded to DH). Additional support was provided by the Canadian Institutes of Health Research (CIHR), the Vanier Canada Graduate Scholarship (CDC), a CIHR and Public Health Agency of Canada, Applied Public Health Chair (DH), and an Ontario Institute for Cancer Research Investigator Award (GTF)
Author declarations	MLG reports grants from and served as an advisory board member to pharmaceutical companies that manufacture smoking cessation drugs. DH has provided paid expert testimony in tobacco litigation on behalf of governments and class‐action plaintiffs on issues related to tobacco product science and regulation. The other authors have no competing interests to declare
Notes	New for 2021 update
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	No details of randomization method given
Allocation concealment (selection bias)	High risk	No blinding
Blinding of participants and personnel (performance bias) All outcomes	High risk	No blinding
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Not reported
Incomplete outcome data (attrition bias) All outcomes	Low risk	All followed up
Selective reporting (reporting bias)	Low risk	No evidence of selective reporting