| Reduction in biomarkers of exposure |
| Sakaguchi et al., 2021 (Japan) (53) | Observational, cross-sectional, three-group, multi-centre study | Examine tobacco smoke related BoE (cotinine and NNAL), BoPH and pulmonary functions relevant to smoking-related diseases | Exclusive NTV users (n = 259), CC (n = 100), NS (n = 100); age = 20–65, male and female, BMI: < 18.5, ≥ 18.5 to < 25.0, ≥ 25.0 | NTV | Significantly higher levels of cotinine, total NNAL, and 2,3-d-TXB2, lower levels of FEV1 and FEV1 percentage observed among NTV users compared to the NS group indicating sustained reduction in exposure to harmful substances of tobacco smoke. |
| Gale et al., 2022 (UK) (52) | Parallel group, open label, ambulatory pseudo-randomized clinical trial (RCT), (1 Year) | To investigate changes in BoE and BoPH levels in current smokers and smokers who switched to THP in comparison to smokers who have quit tobacco and never users | ITT: Group A (n = 78), Group B (n = 197), Group D (n = 190), Group E (n = 40); a Healthy male or female adult current smokers | glo™ THP, NRT or varenicline | THP users: Sustained reduction in BoE levels and participants who quit smoking, the reductions were similar for both groups. |
| Haswell et al., 2023 (UK) (54) | Cross-sectional confinement study | Assessing BoPH, BoE, and physiological measures in EC users for at least 6 months in current, former, and never smokers | n = 213; age = 19–55 years | EC (Vuse Pod or Vuse ePen3) |
Exclusive EC users: exposed to lower levels of tobacco smoke toxicants (MHBMA, HMPMA, 3-HPMA, NNN, COHb, sICAM-1 and 11-dTXB2), study detected low levels of biomarkers of potential harm (BoPH) in three out of seven EC users when compared to CC users. Specifically, COHb, sICAM-1, and 11-d-TXB2 were less in EC users. Additionally, solus Vuse EC users showed less exposure to tobacco toxicants compared to smokers.
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| Health impact of smoke-free alternative products |
| Edmiston et al., 2022, (USA) (61) | Parallel-group, open-label, RCT (24 weeks) | Comparing BoE to HPHC and BoPH in adult smokers who switched to EVPs vs. those who continued smoking | Adult smokers (n = 450) | EVPs and Mark Ten Bold Classic, Mark Ten Bold Menthol |
Exclusive use of EVPs leads to statistically significant reductions (p < 0.05) for WBC count, 11-dTXB2, and sICAM in both test groups. Several significant changes in measures of pulmonary function.
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| Hajat et al., 2022 (22) | Systematic review and meta-analysis | To assess disease end points associated with the use of ENDS | n = 755 studies | ENDS | ENDS were not causative for harmful CVD outcomes, beneficial for hypertensive patients. Switching to EC resulted in reduced exacerbations of COPD, without long-term deterioration in lung function. |
| Cobb et al., 2021 (USA) (62) | Four-arm, parallel-group, RCT (24 weeks) | Effect of ENDS and a non-nicotine cigarette substitute on tobacco toxicant exposure and cigarette consumption | n = 520; age = 21–65 years | ENDS | Use of ENDS reduces the urinary NNAL levels. |
| Begic et al., 2023 (Bosnia & Herzegovina, Japan, Poland, Arizona, Florida, Kentucky, Nebraska, Nevada, North Carolina, Ohio, Tennessee, Texas, Virginia, Germany) (56) | Systematic review | The effect of HnB tobacco products on the cardiovascular system | n = 3740 (25 studies); age ≥ 18 years | HnB | Exclusive use of HnB tobacco products results in significant reductions in BoE and favorable changes in blood pressure, arterial stiffness parameters, myocardial deformation as compared with TC. |
| Feng et al., 2024 (China) (63) | Systematic review and meta-analysis | Comparison of bladder carcinogenic biomarkers in the urine of TC and EC users | n = 16876 (six retrospective study meta-analysis) patients, 10 high evidence studies | EC | Urinary bladder cancer markers (PAHs, VOCs, and TSNAs) were significantly higher in traditional tobacco users than in EC users. |
| Thiem et al., 2023 (Germany) (58) | Systematic review and meta-analysis | Impact of electronic and conventional cigarettes on periodontal health | n = 16 studies | EC | EC use might be considered a healthier alternative to CC smoking as 0.33 fold reduced chances of BoP is observed. CC smoking enhances levels of PI, PD, AL, MBL and pro inflammatory mediators. |
| Brinchmann et al., 2023 (Norway) (64) | Systematic review | Health outcomes in snus users during pregnancy | 18 cohort studies (N = 42–1006398) | Snus | Enhanced risk of neonatal apnea, stillbirths, premature births, moderately premature birth, less birth weight, oral cleft malformations in snus-users. Risk of early neonatal mortality, altered heart rate. Enhanced chances of caesarean sections, risk of neonatal mortality in snus-users. |
| Hajek et al., 2022 (England, Scotland) (65) | RCT | EC vs. nicotine patches for smoking cessation in pregnancy | n = 1140 (EC, n = 569 or nicotine patches, n = 571) | EC, nicotine patch and NRT | EC showed more effectiveness (6.8% quit rate) than nicotine patch (3.6% quit rate) with similar safety profile. Less frequent low birth rate and low birth weight in EC group (9.6%) compared to NRT (14.8%). |
| Potential of smoking cessation or reduction |
| Vanderkam et al., 2022 (France) (8) | Systematic review and meta-analysis | The duration of the effectiveness of EC on smoking cessation and reduction in daily cigarette consumption. | 7 RCTs, smokers; age ≥ 18 | Nicotinic EC, non-nicotine EC, varenicline, bupropion and NRT | Nicotine EC vs. non-nicotine EC and NRT were effective on smoking cessation and reduction in daily cigarette users. |
| Tattan-Birch et al., 2023 (England) (9) | Two-group, parallel arm, pragmatic RCT (12-week) | ECs to Augment Stop Smoking In-person Support and Treatment with Varenicline (E-ASSIST) | n = 92; avg. age = 43.9 years; women 52% (25), men 48% (23); control: women 50% (22), men 50% (22) | EC and Varenicline | 9–12 weeks of abstinence in EC-varenicline group (47.9%); 31.8% only use varenicline. Relapse rate: 43% lower risk of relapse in EC-varenicline group than only varenicline group. 59.8% encountered at least one AE 44.6% sleep disturbance, 34.8% nausea, and 27.2% reported throat or mouth irritation. |
| Funk et al., 2023 (USA) (47) | Randomized study | Examining subjective and behavioral preferences for an e-cigarette and HTP relative to participants UBC | n = 22 (African American (n = 12) and White (n = 10)) | EC and HTP | African American and White smokers substitute UBC for EC or HTP. Behavioral preference for EC (42.9%), followed by HTP (38.1%), and UBC (19.1%). |
| Lindson et al., 2023 (UK) (51) | Meta-analysis | Pharmacological and EC interventions for smoking cessation in adults | n = 319 randomised studies (835 study arms; 157,179 participants) | NRT, EC, varenicline, cytisine, bupropion or nortriptyline | Nicotine EC, varenicline and cytosine associated with higher quit rates than control. |
| Harm reduction for non-users (bystanders) |
| Kawasaki et al., 2023 (Japan) (66) | RCT | Assessment of exposure and DNA damage from second-hand smoke using potential biomarker in urine | n = 746 non-smokers (to detect passive smoking) | HTPs | The NNAL levels in HTPs are one-fifth of the CCs, so the risk is comparatively lower in HTP sticks. |
| Tane et al., 2024 (67) | Review and comparative analysis | Comparative analysis of PM generated in CC and HTP's - mainstream and environmental emissions |
| HTP | Indoors, the number of particles generated from CS is much larger than those from HTPs by a factor of 3–6. From HTPs there was higher volatility of the PM. |
