Goniewicz 2017.

Study characteristics
Methods	Design: Longitudinal within‐subjects observational Recruitment: Advertisements in the media, the internet, posted advertisements in clinics and offices, and by word of mouth Setting: University, Poland Study start date: March 2011; Study end date: June 2011
Participants	Total N: 22 started out and 2 dropped out in the first week due to an adverse event (nausea) and inability to commit to clinic visits. This resulted in analytic sample of 20 Inclusion criteria: 18 years or older, current daily cigarette smokers (> 5 cpd within the last 12 months) May have had interest in quitting smoking, in good health (at the clinic screening visit) Able to communicate in Polish Able to use an e‐cigarette safely Exclusion criteria: Diagnosed as having asthma, COPD, hypertension, inhaled allergies, chronic heart disease, or cancer were taking a cardiac medication were pregnant 60% women; mean age 31; mean cpd 16; mean FTND 3.9 Motivated to quit: At the time of screening, 95% of participants (n = 19) reported planning to quit smoking, with 80% (n = 16) reporting that they have made at least 1 quit attempt prior to involvement in the study E cigarette use at baseline: Not reported
Interventions	EC: Cig‐a‐like Pen‐style M201 e‐cigarettes for 2 weeks, with an automatically‐operated battery with an output power of 4.6 Volts (280 mAh) and the heating element resistance of 3.6 – 3.8 Ohms. At baseline, provided with EC (M201 Mild, Poland) with 20 tobacco‐flavoured cartridges a week containing 11.0 ± 1.5 mg of nicotine in a mixture of propylene glycol and vegetable glycerin (50:50). Encouraged to substitute their regular cigarettes with the e‐cigarette for 2 weeks and refrain from smoking
Outcomes	Day 7, Day 14 Adverse events and biomarkers: Biomarkers were metabolites of 13 major carcinogens and toxicants in cigarette smoke: 1 tobacco‐specific nitrosamine (NNK), eight volatile organic compounds (1.3‐butadiene, crotonaldehyde, acrolein, benzene, acrylamide, acrylonitrile, ethylene oxide, and propylene oxide), and 4 polycyclic aromatic hydrocarbons (naphthalene, fluorene, phenanthrene, and pyrene) Questionnaire on ‘health’: At each visit, participants were asked, “In the last week, have you experienced any of the following symptoms?”, while providing a response of “never,” “rarely,” or “often” to the following list of health effects: daytime cough, difficulty concentrating, difficulty breathing during sleep, difficulty sleeping, dizziness, headache, irritability, nausea, nighttime cough, chest pain, phlegm, shortness of breath, tightness in chest, visual disturbances, and wheezing. Responses of “rarely” or “often” were combined to indicate presence of an adverse health effect Expired CO Other outcomes measured: 7 nicotine metabolites (3‐Hydroxycotinine, Cotinine, Cotinine N‐Oxide, Nicotine N‐Oxide, Norcotinine, Nornicotine, Nicotine) Revised Minnesota Nicotine Withdrawal Scale (MNWS‐R) administered to measure ‘withdrawal symptoms’ (0‐5 rating scale)
Study funding	“This work was supported by the Ministry of Science and Higher Education of Poland (grant number N N404 025638). Instrumentation and analytical chemistry at UCSF was supported by the National Institutes of Health, P30 DA012393 and S10 RR026437. The study sponsor had no involvement in the study design, collection, analysis, and interpretation of data, the writing of the manuscript or the decision to submit the manuscript for publication.”
Author declarations	"MLG was a faculty member of the Medical University of Silesia, Poland during the study. He received a research grant from Pfizer, a pharmaceutical company that markets smoking cessation medications. MLG and NLB have been consultants to pharmaceutical companies that market smoking cessation medications. NLB has been an expert witness in litigation against tobacco companies. The other authors declare no potential conflicts of interest."
Notes	New for 2020 update
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	High risk	Not randomized
Allocation concealment (selection bias)	High risk	Not randomized
Incomplete outcome data (attrition bias) All outcomes	Low risk	2 dropouts – 1 for nausea, 1 could not complete clinic visits. Analysis based on 20 completers
Selective reporting (reporting bias)	Low risk	All outcomes reported