Table 2.
Characteristics of the included cohort studies
| Study and Year | Location | Exposure | Population | Comparison | Follow-up | Outcomes | Adjusted factors | Lost to follow-up (%) |
|---|---|---|---|---|---|---|---|---|
| follow-upShi et al.37 (2016) | USA | Ever nicotine EC users (n=82) | 2454 current adult smokers | Non-EC users (n=936) | 1 year | Probability of smoking cessation | Demographics and baseline cigarette dependence level | 53.3 |
| Biener et al.38 (2015) | USA | Ever nicotine EC users, intensive (n=111), intermittent (n=220) | 695 smokers were categorized as intensive, intermittent and non-EC users | Non-EC users (n=364) | 2 years | Probability of smoking cessation | Demographics and tobacco dependence | 49.4 |
| Manzoli et al.39 (2015) | Italy | Ever nicotine EC users (n=223) | 1355 adult (aged 30–75 years) smokers | Non-EC users (n=480) | 2 years | Probability of smoking cessation | Sociodemographic factors alcohol use and years of smoking | 31.2 |
| Zhuang et al.40 (2016) | USA | Ever nicotine EC users: long-term (n=72) short-term (n=456) | 2028 smokers were categorized as long-term and short-term EC users | Non-EC users (n=1500) | 2 years | Probability of smoking cessation | Sociodemographics, smoking status and intention to cessation | 32.6 |
| Pasquereau et al.41 (2017) | France | Ever nicotine EC users (n=252) | 2057 smokers aged 15–85 years | Non-EC users (n=1805). | 6 months | Probability of smoking cessation | Socioeconomic variables and smoking behaviors | 31.4 |
| Al-Delaimy et al.42 (2015) | USA | Ever nicotine EC users (n=236) | 1000 adult smokers | Non-EC users (n=177) | 1 year | Probability of smoking cessation | Sociodemographic characteristics | 60.0 |
| Kalkhoran et al.43 (2019) | USA | Daily nicotine EC users (n=299), non-daily EC users (n=1523) | 8218 adult smokers were categorized as daily and non-daily EC users | Non-EC users (n=6379) | 1 year | Probability of smoking cessation | Sociodemographic characteristics and smoking status | 2.0 |
| Jackson et al.44 (2019) | UK | Nicotine EC users (n=292) | 1709 adult smokers (aged ≥16 years) | Non-EC users (n=1089) | 1 year | Probability of smoking cessation | Sociodemographics, smoking status, motivation and quit attempts | 9.8 |
| Kalkhoran et al.45 (2019) | USA | Nicotine EC users (n=762) | 4948 adult smokers | Non-EC users (n=4156) | 1 year | Probability of smoking cessation | Sociodemographics, smoking status, education, region, and nicotine dependence | <4.0 |
| Wills et al.46 (2016) | USA | Nicotine EC users (n=215) | 2338 non-smoking students (mean age 14.7 years) | Non-EC users (n=926) | 1 year | Probability of smoking initiation | Age, ethnicity and rebelliousness | 4.20 |
| Aleyan et al.47 (2017) | Canada | Non-susceptible current nicotine EC users (n=73) | 9501 grade 9–11 non-smoking students | Non-susceptible non-current EC users (n=6616) | 2 years | Probability of smoking initiation | Gender, grade, ethnicity and social risk factors | 21.1 |
| Goldenson et al.48 (2017) | USA | Low nicotine EC users (n=52), medium (n=35), high users (n=21) | 3252 grade 10–11 non-smoking students | Placebo-EC users (n=73) | 6 months | Probability of smoking initiation | Interpersonal, intrapersonal and demographic factors | 5.0 |
| Leventhal et al.49 (2015) | USA | Ever nicotine EC users (n=222) | 2530 non-smoking teenagers (mean age=14.1 years) | Non-EC users (n=2308) | 6 months 12 months | Probability of smoking initiation | Sociodemographic, environmental and intrapersonal risk factors | 1.1 |
| Primack et al.50 (2015) | USA | Ever nicotine EC users (n=16) | 694 non-smokers aged 16–26 years, attitudinally non-susceptible to smoking | Non-EC users (n=628) | 1 year | Probability of smoking initiation | Sociodemographic factors and maternal educational level | 30.3 |
| Barrington-Trimis et al.51 (2016) | USA | Nicotine EC users (n=146) | 146 non-smokers (mean age 17.4 years) | Frequency matched non-EC users (n=152) | 16 months | Probability of smoking initiation | Gender, ethnicity and grade | 30.0 |
| Barrington-Trimis et al.52 (2018) | USA | Nicotine EC users (n=673) | 6258 non-smoking adolescents | Non-EC users (n=3891) | 2 years | Probability of smoking initiation | Gender, race/ethnicity, grade, cohort | 1.8 |
| Primack et al.53 (2018) | USA | Ever nicotine EC users (n=16) | 1506 non-smokers aged 18–30 years | Non-EC users (n=899) | 18 months | Probability of smoking initiation | Sociodemographic, personal, and environmental covariates | 39.2 |
| Unger et al.54 (2016) | USA | Ever nicotine EC users (n=42) | 1056 past 30-day non-smokers (mean age 22.7 years) | Non-EC users (n=1014) | 1 year | Probability of smoking initiation | Age, sex, and past-month use of alcohol and other tobacco products | 7.8 |
| Hammond et al.55 (2017) | Canada | Past 30-day nicotine EC users (n=487) | 17318 non-smoking adolescents and young adults | Non past-30 EC users (n=16831) | 1 year | Probability of smoking initiation | Sociodemographic and smoking status | 9.5 |
| Spindle et al.56 (2017) | USA | Ever nicotine EC users (n=153) | Non-smoking youths (n=2316) | Non-EC users (n=2163) | 1 year | Probability of smoking initiation | Anxiety, depression peer deviance and smoking status | 17.8 |
| Miech et al.57 (2017) | USA | Ever nicotine EC users | Non-smoking youths (n=246) | Non-EC users | 1 year | Probability of smoking initiation | Sociodemographic characteristics and parental education | 57.8 |
| Chien et al.58 (2019) | Taiwan | Ever nicotine EC users (n=661) | 12954 non-smoking students | Non-EC users (n=879) | 2 years | Probability of smoking initiation | Sociodemographic characteristics and smoking status | 10.1 |
| Berry et al.59 (2019) | USA | Ever nicotine EC users (n=527) | Non-smoking youths (n=6123) | Non-EC users (n=5290) | 2 years | Probability of smoking initiation | Sociodemographic characteristics, smoking status and behaviors | 5.0 |
| Mcmillen et al.60 (2019) | USA | Ever nicotine EC users (n=195) | Non-smoking youths (n=5776) | Non-EC users (n=5473) | 1 year | Probability of smoking initiation | Demographic variables and psychosocial predictors | 1.9 |
EC: electronic cigarette. NRT: nicotine replacement therapy.