Etter 2014

Methods	Design: Longitudinal Internet survey Recruitment: Via websites selling or informing about ECs and online EC forums Setting: Online survey (open to all nationalities; of respondents, 34% US, 24% France, 8% UK, 6% Switzerland, 28% other countries) Inclusion criteria: Aged 18 years and older Exclusion criteria: none stated
Participants	One‐month survey Total N: 477, mean age 42, 41% women, 59% had a diploma giving access to university, 28% daily or occasional smokers, 76% daily EC users. 50/477 occasional or daily smokers at baseline One‐year survey Total N: 367, mean age 43, 42% women, 59% had a diploma giving access to university, 24% daily or occasional smokers, 79% daily EC users. 35/367 occasional or daily smokers at baseline
Interventions	Observational; no specific intervention. Participants that had completed a baseline questionnaire were emailed one month and one year later and asked to provide follow‐up data on EC use and smoking behaviour
Outcomes	From among those that were smoking cigarettes at baseline 7‐day PP abstinence from smoking at 12 months Smoking consumption (change from baseline) at 12 months
Notes
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	High risk	Prospective cohort
Allocation concealment (selection bias)	High risk	Not randomized
Blinding of participants and personnel (performance bias) All outcomes	Low risk	Although there is no blinding, the study design and lack of intervention or contact with researchers mean that there is unlikely to be significantly impact on performance
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Although there is no blinding, the study design and lack of intervention or contact with researchers mean that there is unlikely to be significantly impact on detection
Incomplete outcome data (attrition bias) All outcomes	High risk	28% (N = 367) for those who answered the baseline survey (N = 1329) provided data at 1‐year follow‐up
Selective reporting (reporting bias)	Unclear risk	Unable to determine prespecified outcomes