Table 5.
Description of studies, level of evidence and quality for health outcomes from ENDS
| Benefit or harm | Reference | Country | Study design and number of subjects, country | Key outcomes assessed | Impact on health outcome | Level of Evidence | Quality Rating |
|---|---|---|---|---|---|---|---|
| Cardiovascular | |||||||
| Benefit | Farsalinos et al. effect of continuous smoking reduction and abstinence on blood pressure and heart rate in smokers switching to electronic cigarettes | Italy | Prospective, double-blind, controlled, three-arm RCT on 145 hypertensive smokers switching to EC | Clinic measured SBP and HR | Reduced SBP (from 141 to 132 mmHg, p < 0.001) in hypertensives switching to EC at 12 months; those continuing to smoke had no reduction | 1B | Good |
| Harm | Alzahrani, et al. association between electronic cigarette use and myocardial infarction | United States | Cross-sectional survey on 6904 subjects | Self-reported MI | Self-reported daily EC users more likely to report MI compared with never EC users (OR = 1.79; 95% CI 1.20–2.66). Compared to never users of e-cigarettes and cigarettes, daily dual users of e-cigarettes and cigarettes were more likely to have an MI (OR = 4.62) | 2C | Poor |
| Harm | Farsalinos et al. is e-cigarette use associated with coronary heart disease and myocardial infarction? | Italy | Cross-sectional survey in 2016 (n = 33,028) and 2017 (n = 26,742) | Self-reported MI and CHD | Self-reported daily EC use not associated with MI (OR = 1.35; 95% CI 0.80–2.27) compared with never EC use after accounting for dual use and former smoking; no association between EC use and CHD compared with never EC use (OR = 1.31; 95% CI 0.79–2.17) | 2C | Fair |
| Harm | Osei, et al. association between e-cigarette use and cardiovascular disease among never and current combustible-cigarette smokers | United States | Cross-sectional survey on 449,092 participants | CVD (defined as Self-reported CHD, MI, stroke) | Self-reported EC using never-smokers had no increased CVD (OR = 1.04; 95% CI 0.63–1.72) or premature CVD (OR = 1.01; 95% CI 0.56–1.83) compared with never EC users; EC using former-smokers were more likely to report CVD (OR = 1.36; 95% CI 1.18–1.56) and premature CVD (OR = 1.45; 95% CI 1.20–1.74) compared with never EC users. Dual smoking and EC use was associated with higher CVD (OR = 1.36; 95% CI 1.18–1.56) | 2C | Poor |
| Harm | Parekh, et al. risk of stroke with e-cigarette and combustible cigarette use in young adults | United States | Cross-sectional survey on 161,529 participants aged 18−44 years | Self-reported stroke | Self-reported EC using never-smokers had no higher risk of stroke (OR = 0.69, 95% CI 0.34, 1.42) compared with nonsmokers; risk of stroke was lower for EC users compared with current exclusive smokers (OR = 0.43, 95% CI 0.20, 0.93). Current EC using former smokers had increased odds of stroke (OR = 2.54; 95% CI 1.16–5.56) compared with never -smokers | 2C | Fair |
| Benefit | Polosa, et al. blood pressure control in smokers with arterial hypertension who switched to electronic cigarettes | Italy |
Observational study of 89 hypertensive smokers who quit or reduced tobacco consumption by switching to EC |
Office SBP and DBP | A significant reduction in median SBP (from 140 to 130 mmHg; p < 0.001) and DBP (from 86–80 mmHg; p = 0.006) at 12-month follow-up in the exclusive EC group. No change in SBP or DBP seen in reduced cigarette consumption dual users at 12 months | 3B | Good |
| Respiratory | |||||||
| Harm | Bowler et al. Electronic cigarette use in US adults at risk for or with COPD: analysis from two observational cohorts | United States |
Pooled results from two cohort studies in 4,596 current or former smokers Aged 45–80 with, or at risk of, COPD |
COPD respiratory symptoms or disease progression (GOLD criteria used to assess COPD spirometric severity) | Self-reported ever use of EC associated with 8% (± 2%) increased prevalence of chronic bronchitis and (in 1 cohort) COPD exacerbations compared with never EC users (p = 0.01); after 5 years, no increase in progression of lung disease or decline in lung function (in one cohort). Adjusted for but not excluding current smokers | 2A | Good |
| Benefit | Polosa et al. health effects in COPD smokers who switch to electronic cigarettes: a retrospective-prospective 3-year follow-up | Italy | Prospective cohort study of 44 COPD smokers switching to EC use | COPD exacerbations, post-bronchodilator lung function, CAT scores, 6-min walking distance | Improvements in COPD exacerbation rates (p = 0.004), CAT scores (p = 0.019) and 6-min walk distance (p = 0.001) in EC users compared with continued smokers after 36 months | 2B | Good |
| Harm | Lappas et al. short‐term respiratory effects of e‐cigarettes in healthy individuals and smokers with asthma | Greece | Cohort study of 54 dual smokers (EC and smoking), 27 (50%) with mild asthma (MA), 27 (50%) no asthma, underwent a control session (no liquid, no resistor coil inside e-cigarette cartridge) and an experimental session of EC using standardized puffing settings | Impulse oscillometry impedance (Z), resistance (R), reactance (X) and fractional exhaled nitric oxide (FeNO) were measured before and 0, 15 and 30 min after control and experimental sessions | MA group exhibited higher baseline values and more prominent effect after EC use using standardized puffing sessions vs. healthy participants after EC use for respiratory system total impedance at 5 Hz (p = 0.022), respiratory system resistance at 5 Hz (p = 0.010) and respiratory system resistance at 10 Hz (p = 0.013). Fractional exhaled nitric oxide decreased significantly in both groups (p < 0.001) | 2B | Poor |
| Benefit | Polosa et al. evidence for harm reduction in COPD smokers who switch to electronic cigarettes | Italy | Retrospective chart review with 12 and 24 month follow-up on 48 heavy smokers with COPD invited to switch to e-cigarettes | Verified COPD exacerbations in previous 12 months | Reduction in annual COPD exacerbations for heavy smokers with COPD switching to EC (mean 2.3 at baseline to 1.8; p = 0.002) at 12 months and to 1.4; p < 0.001) at 24 months,: no change in COPD exacerbations for those not switching | 2C | Good |
| Benefit | Miler et al. changes in the frequency of airway infections in smokers who switched to vaping: results of an online survey | Germany | Cross-sectional survey of 914 smokers who switched to vaping for at least 2 months | Self-reported respiratory infections (e.g., common cold) | Among those who switched to EC, 66% (95% CI 62.9–69.0) reported improvement in respiratory infections, 29% reported no change, 5% reported worsening | 2C | Poor |
| Harm | Bhatta et al. association of e-cigarette use with respiratory disease among adults: a longitudinal analysis | United States | Cross-sectional survey of 705,159 participants | Self-reported chronic bronchitis, emphysema, COPD | Among never smokers, current self-reported EC use associated with chronic bronchitis, emphysema and COPD compared with never EC users (OR = 1.75, 95% CI 1.25–2.45); daily EC use had higher odds (OR = 2.64, 95% CI 1.43, 4.89) | 2C | Poor |
| Harm | Cho et al. association between electronic cigarette use and asthma among high school students in South Korea | South Korea | Cross-sectional survey of 35,904 high school students | Self-reported asthma diagnosis | Among self-reported never smokers, current EC use associated with asthma (OR = 2.74; 95% CI 1.30–5.78) compared with never EC users | 2C | Poor |
| Harm | Choi, Bernat e-cigarette use among Florida youth with and without asthma | United States | Cross-sectional survey of 36,085 high school students | Self-reported asthma and asthma attack | Among those with asthma, self-reported past 30-day EC use (any quantity) associated with asthma attacks (OR = 1.78, 95% CI 1.20–2.64) in the past 12 months compared with non EC users in past 30 days (adjusted for days smoked cigarettes in the past 30 days but smokers not excluded) | 2C | Poor |
| Harm | Kim et al. active, passive, and electronic cigarette smoking is associated with asthma in adolescents | South Korea | Cross-sectional survey of 216,056 adolescents aged 12–18 years | Self-reported asthma | Self-reported EC use group associated with higher prevalence of asthma (OR = 1.13; 95% CI 1.01–1.26) compared with never EC users (adjusting for active, passive cigarette use); greater use of e-cigarettes associated with asthma, 1–5 days/month (OR = 1.39; 95% CI 1.19–1.61), 6–19 days/month (OR = 1.31; 95% CI 1.08–1.61) and > 20 days/month (OR = 1.58; 95% CI 1.40–1.78) compared with never EC use | 2C | Poor |
| Harm | Osei et al. association between E-cigarette use and chronic obstructive pulmonary disease by smoking status: behavioral risk factor surveillance system 2016 and 2017 | United States | Cross-sectional survey on 5454 participants | Self-reported COPD diagnosis |
Self-reported non-current smokers using EC associated with a COPD diagnosis (OR = 2.94, 95% CI 1.73–4.99) compared with non-EC use. Compared with never smokers who never used EC, dual users (smoking and EC) had the highest odds of COPD (OR = 6.89, 95% CI = 6.29, 7.55) Former smoking was not excluded or accounted for |
2C | Poor |
| Harm | Perez et al. adult e-cigarettes use associated with a self-reported diagnosis of COPD | United States | Cross-sectional survey of 32,320 adults and adolescents aged 12–17 years | Self-reported COPD diagnosis | Self-reported EC users had greater odds of COPD than non- EC users (OR = 1.43, 95% CI 1.12–1.85) in adults and children combined | 2C | Poor |
| Harm | Schweitzer et al. e-cigarette use and asthma in a multiethnic sample of adolescents | United States | Cross-sectional survey of 6,082 adolescents | Self-reported asthma diagnosis | Current self-reported EC use associated with asthma (OR = 1.48; 95% CI 1.24–1.78) and with previous asthma (OR = 1.20; 95% CI 1.00–1.44) compared with never EC use, (controlling for but not excluding current cigarette smoking, or former smoking) | 2C | Poor |
| Harm | Wills et al. e-cigarette use and respiratory disorder in an adult sample | United States | Cross-sectional random-dial telephone survey on 8087 adults | Self-reported asthma or COPD diagnosis | Self-reported ever EC use associated with asthma in current non-smokers (OR = 1.33, 95% CI 1.00–1.77, p < 0.05) but not in smokers (OR = 0.92, 95% CI 0.73–1.15, EC use was not associated with COPD in current non-smokers (OR = 2.98, 95% CI 1.51–5.88, p < 0.01) or in current smokers (OR = 1.29, 95% CI 0.94−1.77). There was no significant difference in risk of asthma among dual users compared with sole EC users (OR = 1.00; 95% CI 0.73–1.35) or smokers (OR = 0.99; 95% CI 0.80–1.22). There was increased risk of COPD in smokers (OR = 2.98; 95% CI 2.34–3.78), EC users (OR = 2.58; 95% CI 1.36–4.89) and dual users (OR = 3.92; 95% CI 2.82–5.44) compared with never smokers who never used EC. Ever EC use included any quantity ever used | 2C | Fair |
| Harm | Xie et al. use of electronic cigarettes and self-reported chronic obstructive pulmonary disease diagnosis in adults | United States | Cross-sectional survey of 887,182 participants | Self-reported COPD diagnosis | Self-reported current vapers who never smoked more likely to self-report COPD (OR = 1.47; 95% CI 1.01, 2.12) compared with never smokers (smoked less than 100 cigarettes, not currently vaping) | 2C | Fair |
| Harm | Sommerfeld et al. hypersensitivity pneumonitis and acute respiratory distress syndrome from e-cigarette use | United States | Case study, 18-year-old woman with dyspnea, cough, and pleuritic chest pain after e-cigarette use | Hypersensitivity Pneumonitis and acute respiratory distress syndrome | Case study of single EC user developing sensitivity pneumonitis. Did not report on comorbidities or smoking | 4 | Fair |
| Harm | Khan et al. organizing pneumonia related to electronic cigarette use: a case report and review of literature | United States | Case study, 40-year-old female patient | Organising pneumonia | Single case study of organizing pneumonia, exclusion of other drug use and comorbidities not mentioned | 4 | Poor |
| Harm | Carter et al. Life-threatening vesicular bronchial injury requiring veno-venous extracorporeal membrane oxygenation rescue in an electronic nicotine delivery system user | United States | Case study, 35-year-old female presented to emergency department with chest pain and dyspnea | Vesicular Bronchial Injury | Case study showed vesicular bronchial injury in an EC user. Patient had CVD and other comorbidities and was a former smoker | 4 | Poor |
| Cancer | |||||||
| Benefit | Franco et al. electronic cigarette: role in the primary prevention of oral cavity cancer | Italy | Cross-sectional survey on 65 previous smokers (from outpatient center), e-cigarette smokers (from monthly prevention campaigns), and nonsmokers (from university medical and paramedical staff) | Total number of oral mucosa pre-cancerous (micronucleated) cells from cytologic examination | Self-reported EC users had lower micronuclei compared with smokers based on micronucleated cells/1000 cells (p = 0.001) and micronuclei/1000 cells (p = 0.004) | 2C | Fair |
| Harm | Nguyen et al. oral carcinoma associated with chronic use of electronic cigarettes | United States, Vietnam | Case study of 2 subjects | Oral carcinoma | Two cases of oral carcinoma associated with 13-year use of EC. Description of other risks not detailed eg smoking | 4 | Fair |
| Oral health | |||||||
| Harm | Akinkugbe et al. cigarettes, e-cigarettes, and adolescents’ oral health: findings from the population assessment of tobacco and health (PATH) study | United States | Cross-sectional study on 13,650 adolescents aged 12–17 years | Dental problems (cavities, gum disease or dental stains) | No relationship between self-reported EC use and self-reported dental problems, including among current eEC users (OR = 1.11; 95% CI 0.79–1.55) or ever users (OR = 1.12 95% CI 0.90–1.38) compared with never cigarette or EC users | 2C | Poor |
| Mental health | |||||||
| Harms and benefits | Bandiera et al. depressive symptoms predict current e-cigarette use among college students in Texas | United States | Cohort study of 5445 college students (18–29-year-olds) with 6-month and 1-year follow-ups | Self-reported depressive symptoms | Correlation between depressive symptoms and self-reported EC use was significant at baseline (β = 0.05; p < 0.01), however, EC use did not predict higher depressive symptoms at 6-months or 1-year follow-up | 2B | Good |
| Neutral | Lechner et al. bi-directional associations of electronic and combustible cigarette use onset patterns with depressive symptoms in adolescents | United States | Cohort study of 347 adolescents assessed at baseline, 6- and 12-month follow-up | Self-reported depressive symptoms | Self-reported EC use over previous 12-months associated with greater rate of increase in depressive symptoms over time (b = 1.272, SE = 0.513, p = 0.01) compared with never EC use. Higher frequency of EC use was associated with higher depressive symptoms at 12 months among sustained users (B = 1.611, p = 0.04) | 2B | Good |
| Benefit | Dahal et al. smoking cessation and improvement in mental health outcomes: Do people who quit smoking by switching to electronic cigarettes experience improvement in mental health? | Canada | Cross-sectional survey on 52,956 participants | Self-reported depressive symptoms | Self-reported EC use (any quantity) who were never smokers had higher depressive symptoms (≥ 10 on CES-D 10) compared with never EC users (OR = 2.46; 95% CI 1.82–3.33). Former smokers who used ECs had higher depressive symptoms compared with never smokers (OR = 4.19; 95% CI 2.47–7.11). Former smokers who did not use EC had elevated risk of depressive symptoms as well (OR = 1.41 (95% CI 1.19–1.68) compared to never smokers. EC use included any quantity including experimental use | 2C | Poor |
| Harm | Chadi et al. depressive symptoms and suicidality in adolescents using e-cigarettes and marijuana: a secondary data analysis from the youth risk behavior survey | United States | Cross-sectional survey of 26,821 high school students | Self-reported depressive symptoms and suicidal ideation | Self-reported EC use associated with higher odds of suicidal ideation in past 12 months (OR = 1.23; 95% CI 1.03–1.47) and depressive symptoms (OR = 1.37; 95% CI 1.19–1.57) compared with never EC users, adjusted for current smoking (but former and current smokers were not excluded). No use of validated scores to obtain outcomes | 2C | Poor |
| Harm | Grant et al. e-cigarette use (vaping) is associated with illicit drug use, mental health problems, and impulsivity in university students | United States | Cross-sectional survey of 3572 college and graduate school students | Self-reported mental health issues on PHQ9 scale, self-reported diagnosis of ADHD (Y/N), PTSD (PC-PTSD score), gambling disorder (Y/N), anxiety (GAD-7 score), trait impulsivity plus compulsivity, academic impairments | Self-reported EC use associated with mental health issues, including PHQ-9 score ≥ 10 (Cramer’s V = 0.044; p = 0.052), ADHD (Cramer’s V = 0.073; p < 0.001)), PTSD (PC-PTSD score ≥ 3;Cramer’s V = 0.064; p = < 0.002), gambling disorder (Cramer’s V = 0.081, p < 0.001) and anxiety (GAD-7 > 10; Cramer’s V = 0.066; p < 0.001). They were also more likely to report low self-esteem (Cramer’s V = 0.63; p = 0.002), and endorse traits of impulsivity (attentional: cohen’s d = 0.421; p < 0.001), but not compulsivity (cohen’s d = 0.532; p = 0.043). Did not control for cigarette use. Participation rate of 38% so sample bias possible. No definition of EC use provided | 2C | Fair |
| Harm | King et al. tobacco product use and mental health status among young adults | United States | Cross-sectional survey of 2370 college students | Self-reported depression (higher score, greater depression), stress (higher score, greater perceived stress), mental health diagnosis | Self-reported EC use associated with higher depression score (OR = 1.04; 95% CI 1.01–1.08) compared with never EC use, controlling for 30-day cigarette use. EC use was associated with higher stress score (OR = 1.03 95% CI 1.00–1.05) compared with never EC use, controlling for 30-day cigarette use. Dual use but not former smoking was accounted for | 2C | Fair |
| Harm | Pham et al. electronic cigarette use and mental health: a Canadian population-based study | Canada | Cross-sectional survey of 53,050 participants | Self-reported depressive symptoms, mood and anxiety, mental health, suicidal thoughts, binge drinking | Among female non-smokers, self-reported EC users had increased mood disorders (OR = 1.9; 95% CI 1.2–3.0) and anxiety disorders (OR = 1.9; 95% CI 1.1–3.2) compared with non- EC users. Female current EC use was associated with mood (OR = 1.9 (95% CI 1.4–2.6) and anxiety (OR = 2.6 (95% CI 1.9–3.6)) disorders compared with non EC use. Among male non-smokers, self-reported EC users had increased mood disorders (OR = 1.6; 95% CI 1.0–2.7) compared with non-EC users. Among male smokers, EC use was not associated with mood disorders (OR = 1.4 (95% CI 0.9–2.3). EC use was defined as any quantity within the last 3 months, including experimental use | 2C | Poor |
| Other | |||||||
| Harm | Lanza et al. obesity and cigarette smoking: extending the link to e-cigarette/vaping use | United States | Cross-sectional survey (convenience sample) of 452 participants | Self-reported BMI |
Obese (BMI ≥ 25 kg/m2) participants had higher likelihood of belonging to self-reported Cigarette/EC/Tobacco class compared with the High Substance Use (β = 1.48, OR = 4.40, p < 0.05) and Risky Alcohol Use (β = 1.94, OR = 6.97, p < 0.05) classes; higher likelihood of being classified into the cigarette/electronic tobacco class compared to the low substance use class not significant No detail of definitions for EC use |
2C | Poor |
| Benefit | Miler et al. resolution of recurrent tonsillitis in a non-smoker who became a vaper. A case study and new hypothesis | United Kingdom | Case study of a never-smoker who vapes, with a history of recurrent, chronic tonsillitis | Exacerbations of tonsillitis | After 8 months of vaping, the patient reported absence of exacerbations of tonsillitis, and marked improvement in Tonsillitis. The study did not mention any other comorbidities or exhaustively account for all confounders | 4 | Fair |
| Harm | Maridet et al. the electronic cigarette: the new source of nickel contact allergy of the twenty-first century? | France | Case study on a 52-year old woman | Clinically-determined erythematous, scaly dermatitis | The patient was diagnosed with nickel contact dermatitis associated with the use of an electronic cigarette. The articles also discussed the literature on nickel content in different brands of ECs | 4 | Good |