How effective are electronic cigarettes for reducing respiratory and cardiovascular risk in smokers? A systematic review

[Safety of use of electronic cigarettes: A systematic review of bronchopulmonary, cardiovascular and cancer risks]

As the effects of electronic cigarettes (ECs) have rapidly become widely known, we propose to take stock of recent findings on the bronchopulmonary and cardiovascular adverse effects (AEs) and the risks of cancer occurrence entailed by EC use. METHOD: We carried out a search from 2018 to October 19, 2023 on PubMed, adopting the PRISMA guidelines (2020) with the following keywords in "Titles and abstracts": electronic cigarette, or e-cigarette, or ENDS, AND safety or toxicology or effect or health effect, using "Systematic Review" as a filter. The inclusion criteria were: systematic review of in vitro or in vivo studies in English or French dealing with the risks of ECs for the bronchopulmonary system, the cardiovascular system, or cancer occurrence. CONCLUSION: Twenty-eight systematic reviews on the adverse effects (AE) of electronic cigarettes (EC) in selected humans show that the toxic substances they generate can cause cancers and increase the risk of cardiac and pulmonary disorders. New studies on the potential dangerousness of EC use are essential and urgent.

Association of Cigarette-E-Cigarette Transitions With Respiratory Symptom Resolution

INTRODUCTION

Adults increasingly use e-cigarettes for cigarette cessation because of the perceived reduced risk. While e-cigarette use is associated with reduced toxicant exposure compared with smoking, it is unclear whether transitioning from cigarettes to e-cigarettes is associated with resolution of respiratory symptoms.

METHODS

Data were obtained from the Population Assessment of Tobacco and Health (PATH) study waves 1-5. US adult participants were separated into observations with cigarette-e-cigarette exposure intervals determined from PATH waves 1-2, 2-3, and 3-4. Observations were included if the participant reported exclusively smoking at baseline and reported a baseline cough or wheeze. Mixed-effect Poisson models measured the association between cigarette-e-cigarette transitions over the two-wave exposure interval (from smoking to nonuse, exclusive e-cigarette use, continued smoking, or dual use) and the reported resolution of the participant's cough or wheeze.

RESULTS

Among 5210 (3362 unique) observations, transitioning from cigarettes to e-cigarettes was associated with increased rates of wheeze resolution (incidence rate ratio [IRR] = 1.33; 95% confidence interval [CI] = 1.01 to 1.75) but not cough resolution (IRR = 1.18; 95% CI = 0.93 to 1.50) compared with persistent smoking. Cigarette to dual-use transitions were not associated with improvements in symptom resolution, and those who switched to dual use and maintained or increased their smoking intensity had 15% decreased rates of respiratory symptom resolution compared with persistent smoking.

DISCUSSION

E-cigarette-assisted smoking cessation may increase rates of respiratory symptoms resolution among smokers who completely transition to e-cigarettes; however, there is risk for additional harm among those who initiate e-cigarette use without decreasing their smoking intensity.

IMPLICATIONS

Government agencies are increasingly weighing the risks and benefits of e-cigarette-assisted cigarette cessation given the reduced harm associated with e-cigarette use. This study provides novel evidence that completely transitioning from cigarettes to e-cigarettes is associated with increased rates of resolution from self-reported wheeze symptoms. However, risk exists in e-cigarette-assisted cigarette cessation, as those who transitioned from exclusive cigarette smoking to dual use and did not reduce their cigarette smoking intensity had decreased rates of respiratory symptom resolution compared with persistent smokers.

Brazilian Society of Angiology and Vascular Surgery guidelines on peripheral artery disease

Patients with peripheral artery disease and generalized atherosclerosis are at high risk of cardiovascular and limb complications, affecting both quality of life and longevity. Lower limb atherosclerotic disease is associated with high cardiovascular morbidity and mortality and adequate management is founded on treatments involving patient-dependent factors, such as lifestyle changes, and physician-dependent factors, such as clinical treatment, endovascular treatment, or conventional surgery. Medical management of peripheral artery disease is multifaceted, and its most important elements are reduction of cholesterol level, antithrombotic therapy, control of arterial blood pressure, control of diabetes, and smoking cessation. Adhesion to this regime can reduce complications related to the limbs, such as chronic limb-threatening ischemia, that can result in amputation, and the systemic complications of atherosclerosis, such as stroke and myocardial infarction.

Association between the use of electronic cigarettes and myocardial infarction in U.S. adults

BACKGROUND

Compared with conventional cigarettes, electronic cigarettes are less harmful in some studies. However, recent research may indicate the opposite. This study aimed to determine whether e-cigarette use is related to myocardial health in adults in the U.S.

METHODS

This study used data from the 2020 Behavioral Risk Factor Surveillance System (BRFSS), a cross-sectional survey of adult US residents aged 18 years or older. We examined whether e-cigarette use was related to myocardial infarction byapplying a logistic regression model to calculate odds ratios (ORs) and 95% confidence intervals (CIs).

RESULTS

The final analytical sample included 198,530 adults in the U.S. Logistic regression indicated that U.S. adults who reported being former and some days of e-cigarette use had 23% and 52% greater odds of ever having an MI, respectively, than did those who reported never using e-cigarettes (OR = 1.23, 95% CI 1.08-1.40, p = 0.001; OR = 1.52, 95% CI 1.10-2.09, p = 0.010).

CONCLUSIONS

The results suggest that former and someday users of e-cigarettes probably have increased odds of myocardial infarction in adults in the U.S. Further research is needed, including long-term follow-up studies on e-cigarettes, since it is still unknown whether they should be discouraged.

An Estimation of the Prevalence of Smoking and e-Cigarette Use among U.S. Adults If Menthol Cigarettes and Flavored Cigars Are Banned

INTRODUCTION

People's reaction to the FDA's ban on flavored cigarettes and cigars may be modified by a concurrent ban on flavored e-cigarettes. We aim to estimate the prevalence of smoking and e-cigarette use among U.S. adults under various ban scenarios.

METHODS

We collected the reactions of people who used cigarettes, cigars, and e-cigarettes reactions to three hypothetical ban scenarios, (1) restricting menthol cigarettes and flavored cigars only, or (2) further restricting e-cigarettes with any flavors except menthol or tobacco, or (3) further restricting e-cigarettes with all flavors. The above data were analyzed to identify determinants of reactions and to estimate and calibrate the probabilities of quitting and switching to non-flavored cigarettes and cigars. Afterward, the probabilities were applied to 2018-2019 TUS-CPS respondents to estimate the prevalence of smoking and e-cigarette use.

RESULTS

Compared with the baseline, the prevalence of smoking decreased from 12.6% to 10.5%, and e-cigarette use increased from 2.6% to 3.8% in Scenario No.1. In Scenario No.2 and No.3, the prevalence of smoking was 10.5% and 10.7%, and the prevalence of e-cigarette use were 3.1% and 2.4%, respectively. For black people, the prevalence of smoking decreased from 14.2% in baseline to 8.1%-8.8% in three scenarios.

CONCLUSIONS

The result indicated that for a ban on menthol cigarettes and flavored cigars, a concurrent ban on flavored e-cigarettes with an exemption of menthol flavor could be more effective in encouraging people to quit smoking. Black people may see a disproportionate benefit from all ban scenarios compared with other race/ethics groups.

Nicotine or marijuana vaping exposure during pregnancy and altered immune responses in offspring

Electronic nicotine delivery systems (ENDS) - which include electronic cigarettes or e-cigarettes, or simply e-cigs, and marijuana vaping have become increasingly popular. ENDS devices have been established as one of the tobacco quit methods and promoted to be safer compared to traditional tobacco cigarettes. Emerging evidence demonstrates that e-cigarette and marijuana vape use can be harmful, with potential associations with cancer. Herein, we summarize the level of evidence to date for altered immune response, with a focus on cancer risks in the offspring after maternal use of, or aerosol exposures from, ENDS or marijuana vape during pregnancy. From 27 published articles retrieved from PubMed, we sought to find out identified carcinogens in ENDS aerosols and marijuana vapor, which cross the placental barrier and can increase cancer risk in the offspring. Carcinogens in vaping aerosols include aldehydes, metals, tobacco-specific nitrosamines, tobacco alkaloids, polycyclic aromatic hydrocarbons, and volatile organic compounds. Additionally, there was only one passive vaping exposure case study on a human fetus, which noted that glycerol, aluminum, chromium, nickel, copper, zinc, selenium, and lead crossed from the mother to the offspring's cord blood. The carcinogens (metals) in that study were at lower concentrations compared to the mother's biological matrices. Lastly, we observed that in utero exposures to ENDS-associated chemicals can occur in vital organs such as the lungs, kidneys, brain, bladder, and heart. Any resulting DNA damage increases the risk of tumorigenesis. Future epidemiological studies are needed to examine the effects of passive aerosol exposures from existing and emerging electronic nicotine and marijuana products on developing offspring to cancer.

Population-Based Disease Odds for E-Cigarettes and Dual Use versus Cigarettes

BACKGROUND: E-cigarettes are promoted as less harmful than cigarettes. There has not been a direct comparison of health effects of e-cigarettes or dual use (concurrently using e-cigarettes and cigarettes) with those of cigarettes in the general population. METHODS: Studies in PubMed, EMBASE, Web of Science, and PsychINFO published through October 1, 2023, were pooled in a random-effects meta-analysis if five or more studies were identified with a disease outcome. We assessed risk of bias with Risk Of Bias In Non-randomized Studies of Exposure and certainty with Grading of Recommendations, Assessment, Development, and Evaluations. Outcomes with fewer studies were summarized but not pooled. RESULTS: We identified 124 odds ratios (94 cross-sectional and 30 longitudinal) from 107 studies. Pooled odds ratios for current e-cigarette versus cigarette use were not different for cardiovascular disease (odds ratio, 0.81; 95% confidence interval, 0.58 to 1.14), stroke (0.73; 0.47 to 1.13), or metabolic dysfunction (0.99; 0.91 to 1.09) but were lower for asthma (0.84; 0.74 to 0.95), chronic obstructive pulmonary disease (0.53; 0.38 to 0.74), and oral disease (0.87; 0.76 to 1.00). Pooled odds ratios for dual use versus cigarettes were increased for all outcomes (range, 1.20 to 1.41). Pooled odds ratios for e-cigarettes and dual use compared with nonuse of either product were increased (e-cigarette range, 1.24 to 1.47; dual use, 1.49 to 3.29). All included studies were assessed as having a low risk of bias. Results were generally not sensitive to study characteristics. Limited studies of other outcomes suggest that e-cigarette use is associated with additional diseases. CONCLUSIONS: There is a need to reassess the assumption that e-cigarette use provides substantial harm reduction across all cigarette-caused diseases, particularly accounting for dual use.

Relieving or aggravating the burden: Non-communicable diseases of dual users of electronic and conventional cigarette in Indonesia

INTRODUCTION

Conventional (tobacco) and e-cigarette smoking prevalence is a growing concern in Indonesia. It has worsened as e-cigarettes complement conventional cigarettes, resulting in dual users, potentially causing an additional burden in terms of health.

METHODS

Our study is a secondary data analysis of the 2018 National Basic Health (Riskesdas) Survey. The sample is limited to respondents aged 15-64 years who either only used e-cigarettes (e-cigarette single users), only used conventional cigarettes (conventional cigarette single users) or used both e-cigarettes and conventional cigarettes (dual users) in the last month. The sample size of the data was 174917 individuals. Our analysis utilized the logit and negative binomial regression to test whether the type of smoking behavior was associated with reporting to have a non-communicable diseases (NCDs) and multimorbidity, respectively.

RESULTS

We found that: 1) dual users are positively associated to report having NCDs, such as liver failure (AOR=2.38; 95% CI: 2.32-2.44), diabetes (AOR=1.53; 95% CI: 1.50-1.57), hypertension (AOR=1.49; 95% CI: 1.48-1.51), and gum diseases (AOR=1.74; 95% CI: 1.73-1.74) compared to single users; and 2) e-cigarette single users are positively associated with reporting to have NCDs such as asthma (AOR=3.11; 95% CI: 3.01-3.22) and diabetes (AOR=16.01; 95% CI: 14.57-17.59), and dental problems such as broken teeth (AOR=1.04; 95% CI: 1.03-1.06), and they have disease multimorbidity compared to conventional cigarette single users.

CONCLUSIONS

Simultaneous control of the consumption of e-cigarettes and conventional cigarettes is essential. In addition, it is important to promote policies to increase the price of e-cigarettes and conventional cigarettes to reduce smoking prevalence and prevent dual users. Moreover, as there are negative health consequences for conventional and e-cigarette single users or dual users, the most effective alternative is to stop smoking, not switching products.

Diretrizes sobre doença arterial periférica da Sociedade Brasileira de Angiologia e Cirurgia Vascular

Resumo Pacientes com doença arterial periférica e aterosclerose generalizada apresentam alto risco de complicações cardiovasculares e nos membros, o que afeta sua qualidade de vida e longevidade. A doença aterosclerótica das extremidades inferiores está associada à alta morbimortalidade cardiovascular, sendo necessário para sua adequada terapia realizar o tratamento dos fatores dependentes do paciente, como a modificação no estilo de vida, e dos fatores dependentes do médico, como o tratamento clínico, tratamento endovascular ou cirurgia convencional. A abordagem médica para a doença arterial periférica é multifacetada, e inclui como principais medidas a redução do nível do colesterol, a terapia antitrombótica, o controle da pressão arterial e do diabetes e a cessação do tabagismo. A adesão a esse regime pode reduzir as complicações relacionadas aos membros, como a isquemia crônica que ameaça o membro e pode levar à sua amputação, e as complicações sistêmicas da aterosclerose, como o acidente vascular cerebral e infarto do miocárdio.

Respiratory health effects of e-cigarette substitution for tobacco cigarettes: a systematic review

BACKGROUND

E-cigarettes (electronic nicotine delivery system, ENDS) have been presented as a harm reduction strategy for people who smoke tobacco cigarettes but who cannot achieve abstinence, or for those who wish to continue to enjoy nicotine and the habit of smoking. What are the health effects of the substitution of ENDS for tobacco cigarettes? This systematic review evaluates the evidence of human clinical tests on the respiratory effects of ENDS use in participants who smoke tobacco cigarettes.

METHODS

A registered and published protocol was developed conforming to PRISMA 2020 and AMSTAR2 standards. The literature search was conducted in PubMed, Scopus, and the CENTRAL Cochrane Library and updated to May 2022. Three supplementary searches and a grey literature search were performed. Studies were evaluated with the JBI quality tools and the Oxford Catalogue of Bias. Due to the heterogeneity (diversity) of the studies, a narrative data synthesis was performed on the test findings plus three sub-group analyses.

RESULTS

The review consists of sixteen studies and twenty publications. Spirometry tests comprised the majority of the data. In total, 66 respiratory test measurements were reported, out of which 43 (65%) were not significant. Statistically significant findings were mixed, with 9 tests showing improvements and 14 measuring declines, none of which was clinically relevant. Ten studies were rated at a high risk of bias, and six had some concerns primarily due to inadequate research designs and the conduct of the studies. Reporting bias was documented in thirteen studies.

CONCLUSIONS

Most of the studies showed no difference in respiratory parameters. This indicates that ENDS substitution for smoking likely does not result in additional harm to respiratory health. Due to the low quality of the studies, confidence in the conclusions is rated as low. Robust studies with a longer duration and sufficient power are required to validate any potential benefits or possible harms of ENDS substitution. Registration PROSPERO #CRD42021239094, International Registered Report Identifier (IRRID): DERR1-10.2196/29084.

Characterization and Summarization of the Impact of Electronic Cigarettes on the Cardiovascular System: A Systematic Review and Meta-Analysis

Electronic cigarettes may increase the risk of long-term cardiovascular morbidity. To protect the heart, awareness should be raised of the risks and limits of E-cigarette aerosol exposure. Thus, this systematic review and meta-analysis assessed the cardiovascular risk of e-smoking. This systematic review was conducted by using the Preferred Reporting Items for Systematic Review and Meta-Analysis (PRISMA) statement. We searched PubMed, Embase, Scopus, Web of Science, and Science Direct databases in December 2022 to identify studies investigating e-cigarettes' impact on the heart. The study was supported by meta-analysis and qualitative review. Out of the initial 493 papers, only 15 met the inclusion criteria and were included in the study. The cumulative number of participants in the myocardial infarction (MI) group was 85,420, and in the sympathetic groups in whom the systolic blood pressure (SBP), diastolic blood pressure (DBP), mean blood pressure (MBP), and heart rate (HR) were measured, were 332 cigarette smokers. The control group included the "never use," "non-smokers," and "never smoke." The pooled analysis showed a significant difference between the e-cigarette smokers and the control group regarding the risk of developing MI in former smokers (OR= 0.12; 95% CI: 0.01-1.72, P = 0.12) and never smoked (OR= 0.02; 95% CI: 0.00-0.44, P = 0.01) favoring the control group. The pooled analysis of the included studies showed a significant difference between the e-cigarette smokers with nicotine and the control group regarding the mean difference (MD) of the SBP (MD = 2.89; 95% CI: 1.94-3.84; P < 0.001), the DBP (MD = 3.10; 95% CI: 0.42-5.78; P = 0.02), the MBP (MD = 7.05; 95% CI: 2.70-1.40; P = 0.001), and HF (MD = 3.13; 95% CI: 0.96-5.29; P = 0.005) favoring the control group. We conclude that using e-cigarettes has a detrimental effect on cardiac health. The risk of severe cardiac conditions increases with e-cigarettes. Thus, vaping can do more harm than good. Consequently, the misleading notion that e-cigarettes are less harmful should be challenged.

Smoke and mirrors: Support from psychiatrists for nicotine e-cigarette availability in Australia

The Royal Australian and New Zealand College of Psychiatrists' (RANZCP) 2018 position statement supports increased, regulated availability of e-cigarettes (ECs) as a harm-reduction measure and recommends further research into their use. Aligned with this recommendation, we aimed to critically evaluate the RANZCP's stance on this issue through a literature review focused on the areas identified in the position statement as requiring further investigation: (1) the adverse health effects attributable to ECs; (2) use of ECs for smoking cessation (particularly for people living with severe mental illness); and (3) EC-associated risks for nicotine naïve young people. We identified and summarised evidence of harm attributable to ECs that is particularly relevant to young people through direct adverse health sequelae, onset of nicotine dependence and increased risk of combustible cigarette (CC) use. A small number of studies suggest ECs can be used for harm-reduction purposes in people diagnosed with nicotine dependence and severe mental illness. However, these results must be considered alongside robust evidence supporting the effectiveness of existing pharmacological interventions for smoking cessation in people with severe mental illness. The position statement is in urgent need of review in line with the available evidence.

Clinical testing of the cardiovascular effects of e-cigarette substitution for smoking: a living systematic review

Some persons who smoke have substituted e-cigarettes for tobacco cigarettes, either completely or partially. What effect does this have on cardiovascular functioning? We conducted a living systematic review on human clinical studies measuring the cardiovascular effects of e-cigarette substitution for smoking. The Scopus, PubMed, and CENTRAL Cochrane Library databases were searched on January 31 and April 29, 2021. Three secondary searches and a grey literature search were conducted. Included study designs were randomized controlled trials, quasi-experimental clinical trials, and cohort studies. Risk of bias and study quality were evaluated with the JBI Critical Appraisal tools and the Oxford Catalogue of Bias. The systematic review covered 25 studies comprising 1810 participants who smoked. Twenty studies were rated at high risk of bias, and five as some concerns. A tabular synthesis by direction of effect was conducted due to heterogeneity in the data. Nearly two-thirds of the test analyses indicated that e-cigarette use had no significance difference compared with tobacco cigarettes on heart rate, blood pressure, and in other cardiovascular tests. In two studies, participants with hypertension experienced a clinically relevant reduction in systolic blood pressure after 1 year of e-cigarette use. E-cigarette substitution incurs no additional cardiovascular risks, and some possible benefits may be obtained, but the evidence is of low to very low certainty. An update search on May 30, 2022 retrieved five studies that did not alter our conclusion.Registration PROSPERO #CRD42021239094.

Impact of e-cigarettes as cancer risk: A protocol for systematic review and meta-analysis

BACKGROUND

The use of electronic cigarettes is one of the current public health problems on increasing alert, has been growing at an accelerating rate, and has become a public health emergency. Its importance is explained by the continuous growth and acceleration of oncological rates among all ages versus the absence of high-quality evidence, correlated to the use of nicotine derived products, being at their regular versions or the new ones. Available preclinical data indicate that activation of the sympathetic nervous system by nicotine inhaled from e-cigarettes may stimulate cancer development and growth by several mechanisms, which results can significantly reduce life's quality. This systematic review and meta-analysis protocol aims to clarify the connection between the use of electronic cigarettes by adults over the age of 18 and the development of malignant neoplastic diseases.

METHOD

The proposed systematic review and meta-analysis will be reported conforming to the preferred reporting items for systematic reviews and meta-analyses guidelines. Will include the following studies: case-control or cohort studies showing adults (18 years old age) using e-cigarettes. There will be no language or publication period restrictions. Articles published, but not peer-reviewed, will not be included in the review. Data will be entered in the Review Manager software (RevMan5.2.3). For dichotomous outcomes, we extracted or calculated the OR and 95% CI for each study. In case of heterogeneity (I²>50%), the random-effects model will be used to combine the studies to calculate the OR and 95% CI.

The Respiratory Symptom Experience Scale (RSES): Quantitative Psychometric Assessment and Validation of a New Questionnaire to Assess Respiratory Symptoms in Current and Former Smokers RSES (Preprint)

BACKGROUND

Smokers often experience respiratory symptoms (eg, morning cough), and those who stop smoking, including those who do so by switching completely to electronic nicotine delivery systems (ENDS), may experience reductions in symptoms. Existing respiratory symptom questionnaires may not be suitable for studying these changes, as they are intended for patient populations, such as those with chronic obstructive pulmonary disease (COPD).

OBJECTIVE

This study aimed to develop a respiratory symptom questionnaire appropriate for current smokers and for assessing changes when smokers stop smoking.

METHODS

The Respiratory Symptom Experience Scale (RSES) was derived from existing instruments and subject matter expert input and refined through cognitive debriefing interviews (n=49). Next, for purposes of the quantitative psychometric evaluation, the RSES was administered to smokers (n=202), former smokers (no tobacco use in >6 months; n=200), and switchers (n=208, smokers who switched to ENDS for >6 months), all of whom had smoked for at least 10 years (mean age 33 years). Participants, who averaged 62 (SD 12) years of age, included 28% (173/610) with respiratory allergy symptoms and 17% (104/610) with COPD. Test-retest reliability was assessed by repeat assessment after 1 week in 128 participants.

RESULTS

A generalized partial credit model confirmed that the response options were ordered, and a parallel analysis using principal components confirmed that the scale was unidimensional. With allowance for 2 sets of correlated errors between pairs of items, a 1-factor graded response model fit the data. Discrimination parameters were approximately 1 or greater for all items. Scale reliability was 0.80 or higher across a broad range of severity (standardized scores -0.40 to 3.00). Test-retest reliability (absolute intraclass correlation) was good, at 0.89. RSES convergent validity was supported by substantial differences (Cohen d=0.74) between those with and without a diagnosis of respiratory disease (averaging 0.57 points, indicating that differences of this size or smaller represent meaningful differences). RSES scores also strongly differentiated those with and without COPD (d=1.52). Smokers' RSES scores were significantly higher than former smokers' scores (P<.001). Switchers' RSES scores were significantly lower than smokers' scores (P<.001) and no different from former smokers' scores (P=.34).

CONCLUSIONS

The RSES fills an important gap in the existing toolkit of respiratory symptom questionnaires; it is a reliable and valid tool to assess respiratory symptoms in adult current and former smokers, including those who have switched to noncombusted nicotine products. This suggests that the scale is sensitive to respiratory symptoms that develop in smokers and to their remission when smokers quit or switch to noncombusted nicotine products intended to reduce the harm of smoking. The findings also suggest that switching from cigarettes to ENDS may improve respiratory health.

Electronic Cigarette Use, Misuse, and Harm

Electronic cigarettes (e-cigarettes) are battery-powered devices that use heat to aerosolize a liquid containing a variety of substances (usually nicotine and/or cannabinoids, flavorings, and glycerol or propylene glycol base) that is then inhaled. E-cigarettes are rapidly evolving over time, so the true health effects of e-cigarettes are difficult to study and remain largely unknown. We review the effects of e-cigarettes on nicotine addiction and on pulmonary disease including the effects of dual use and switching from combustible cigarettes to e-cigarettes. Studies show that e-cigarette use can increase the risk to nicotine dependence and combustible tobacco use. Studies show an association between e-cigarette use and pulmonary disease. Some studies suggest reduced harm from e-cigarette use compared with smoking, but this requires further study. Most adults who use e-cigarettes also smoke cigarettes; epidemiologic studies suggest that the combination of e-cigarettes and cigarettes is more harmful than using either product alone.

Chronic health effects associated with electronic cigarette use: A systematic review

Introduction

Over the last decade, e-cigarette use has been on the rise but with growing health concerns. The objective of this systematic review was to update findings for chronic health outcomes associated with e-cigarette use from the 2018 National Academies of Sciences, Engineering, and Medicine (NASEM) report.

Methods

Three bibliographic databases were searched to identify studies comparing the chronic health effects of e-cigarette users (ECU) to non-smokers (NS), smokers, and/or dual users indexed between 31 August 2017 and 29 January 2021. Two independent reviewers screened abstracts and full texts. Data were extracted by one reviewer and verified by a second one. Outcomes were synthesized in a narrative manner using counts and based on statistical significance and direction of the association stratified by study design and exposure type. Risk of bias and certainty of evidence was assessed. The protocol was prospectively registered on Open Science Framework https://osf.io/u9btp.

Results

A total of 180 articles were eligible. This review focused on 93 studies for the 11 most frequently reported outcomes and from which 59 reported on daily e-cigarette use. The certainty of evidence for all outcomes was very low because of study design (84% cross-sectional) and exposure type (27% reported on exclusive ECU, i.e., never smoked traditional cigarettes). Overall, the summary of results for nearly all outcomes, including inflammation, immune response, periodontal and peri-implant clinical parameters, lung function, respiratory symptoms, and cardiovascular disease, suggested either non-significant or mixed results when daily ECU was compared to NS. This was also observed when comparing exclusive ECU to NS. The only notable exception was related to oral health where most (11/14) studies reported significantly higher inflammation among daily ECU vs. NS. Compared to the smokers, the exclusive-ECUs had no statistically significant differences in inflammation orperiodontal clinical parameters but had mixed findings for peri-implant clinical parameters.

Conclusions

This review provides an update to the 2018 NASEM report on chronic health effects of e-cigarette use. While the number of studies has grown, the certainty of evidence remains very low largely because of cross-sectional designs and lack of reporting on exclusive e-cigarette exposure. There remains a need for higher quality intervention and prospective studies to assess causality, with a focus on exclusive e-cigarette use.

Risk and safety profile of electronic nicotine delivery systems (ENDS): an umbrella review to inform ENDS health communication strategies

OBJECTIVES

This umbrella review aims to summarise the evidence about electronic nicotine delivery systems' (ENDS) risk and safety health profile to inform ENDS health communication strategies.

DATA SOURCES AND STUDY SELECTION

Six databases were searched for systematic reviews presenting evidence on ENDS-related health effects. Ninety reviews divided into five categories were included: toxicity=20, health effects=40, role in smoking cessation=24, role in transition to combustible cigarettes (CCs)=13 and industry marketing claims=4.

DATA EXTRACTION

Findings were synthesised in narrative summaries. Meta-analyses were conducted by study type when appropriate. Quality assessment was conducted using the Measurement Tool to Assess Systematic Reviews. The Institute of Medicine's Levels of Evidence Framework was used to classify the evidence into high-level, moderate, limited-suggestive and limited-not-conclusive.

DATA SYNTHESIS

We found high-level evidence that ENDS exposes users to toxic substances; increases the risk of respiratory disease; leads to nicotine dependence; causes serious injuries due to explosion or poisoning; increases smoking cessation in clinical trials but not in observational studies; increases CC initiation; and exposure to ENDS marketing increases its use/intention to use. Evidence was moderate for ENDS association with mental health and substance use, limited-suggestive for cardiovascular, and limited-not-conclusive for cancer, ear, ocular and oral diseases, and pregnancy outcomes.

CONCLUSIONS

As evidence is accumulating, ENDS communication can focus on high-level evidence on ENDS association with toxicity, nicotine addiction, respiratory disease, ENDS-specific harm (explosion, poisoning) and anti-ENDS industry sentiment. Direct comparison between the harm of CCs and ENDS should be avoided.

PROSPERO REGISTRATION NUMBER

CRD42021241630.

Health Effects of Electronic Cigarettes: An Umbrella Review and Methodological Considerations

E-cigarettes are often marketed as a safer alternative to combustible cigarettes. However, their health effects, especially those associated with long-term use, remain largely uncertain. We conducted an umbrella review of the cardiopulmonary and carcinogenic risks of e-cigarette use, distinguishing between short-term and long-term health effects. The search for systematic reviews was conducted across four electronic databases through 25 January 2022. Methodological quality was assessed using the AMSTAR-2 quality appraisal tool. Seventeen systematic reviews, including five meta-analyses, were included in our umbrella review. There was a clear underreporting of e-cigarette devices and e-liquid types, e-cigarette and cigarette exposure, and the health and smoking status of study participants. Overall, the findings suggest that short-term use of e-cigarettes may be associated with acute cardiopulmonary risks, although to a lesser extent than cigarette use. Long-term e-cigarette use may have pulmonary/respiratory benefits in those who switch from chronic cigarette smoking, particularly in individuals with asthma and chronic obstructive pulmonary disease (COPD). Evidence on intermediate and long-term carcinogenic effects is lacking. This umbrella review underscores the urgent need for systematic reviews with better adherence to established reporting guidelines, consistent definitions of duration of e-cigarette use, a focus on newer devices, and accounting for the impacts of former or current smoking.

Saliva and Lung Microbiome Associations with Electronic Cigarette Use and Smoking

The microbiome has increasingly been linked to cancer. Little is known about the lung and oral cavity microbiomes in smokers, and even less for electronic cigarette (EC) users, compared with never-smokers. In a cross-sectional study (n = 28) of smokers, EC users, and never-smokers, bronchoalveolar lavage and saliva samples underwent metatranscriptome profiling to examine associations with lung and oral microbiomes. Pairwise comparisons assessed differentially abundant bacteria species. Total bacterial load was similar between groups, with no differences in bacterial diversity across lung microbiomes. In lungs, 44 bacteria species differed significantly (FDR < 0.1) between smokers/never-smokers, with most decreased in smokers. Twelve species differed between smokers/EC users, all decreased in smokers of which Neisseria sp. KEM232 and Curvibacter sp. AEP1-3 were observed. Among the top five decreased species in both comparisons, Neisseria elongata, Neisseria sicca, and Haemophilus parainfluenzae were observed. In the oral microbiome, 152 species were differentially abundant for smokers/never-smokers, and 17 between smokers/electronic cigarette users, but only 21 species were differentially abundant in both the lung and oral cavity. EC use is not associated with changes in the lung microbiome compared with never-smokers, indicating EC toxicity does not affect microbiota. Statistically different bacteria in smokers compared with EC users and never-smokers were almost all decreased, potentially due to toxic effects of cigarette smoke. The low numbers of overlapping oral and lung microbes suggest that the oral microbiome is not a surrogate for analyzing smoking-related effects in the lung.

PREVENTION RELEVANCE

The microbiome affects cancer and other disease risk. The effects of e-cig usage on the lung microbiome are essentially unknown. Given the importance of lung microbiome dysbiosis populated by oral species which have been observed to drive lung cancer progression, it is important to study effects of e-cig use on microbiome.

Transcriptomic Evidence That Switching from Tobacco to Electronic Cigarettes Does Not Reverse Damage to the Respiratory Epithelium

The health benefits of switching from tobacco to electronic cigarettes (ECs) are neither confirmed nor well characterized. To address this problem, we used RNA-seq analysis to compare the nasal epithelium transcriptome from the following groups (n = 3 for each group): (1) former smokers who completely switched to second generation ECs for at least 6 months, (2) current tobacco cigarette smokers (CS), and (3) non-smokers (NS). Group three included one former cigarette smoker. The nasal epithelial biopsies from the EC users vs. NS had a higher number of differentially expressed genes (DEGs) than biopsies from the CS vs. NS and CS vs. EC sets (1817 DEGs total for the EC vs. NS, 407 DEGs for the CS vs. NS, and 116 DEGs for the CS vs. EC comparison). In the EC vs. NS comparison, enriched gene ontology terms for the downregulated DEGs included cilium assembly and organization, whereas gene ontologies for upregulated DEGs included immune response, keratinization, and NADPH oxidase. Similarly, ontologies for cilium movement were enriched in the downregulated DEGs for the CS vs. NS group. Reactome pathway analysis gave similar results and also identified keratinization and cornified envelope in the upregulated DEGs in the EC vs. NS comparison. In the CS vs. NS comparison, the enriched Reactome pathways for upregulated DEGs included biological oxidations and several metabolic processes. Regulator effects identified for the EC vs. NS comparison were inflammatory response, cell movement of phagocytes and degranulation of phagocytes. Disease Ontology Sematic Enrichment analysis identified lung disease, mouth disease, periodontal disease and pulmonary fibrosis in the EC vs. NS comparison. Squamous metaplasia associated markers, keratin 10, keratin 13 and involucrin, were increased in the EC vs. NS comparison. Our transcriptomic analysis showed that gene expression profiles associated with EC use are not equivalent to those from non-smokers. EC use may interfere with airway epithelium recovery by promoting increased oxidative stress, inhibition of ciliogenesis, and maintaining an inflammatory response. These transcriptomic alterations may contribute to the progression of diseases with chronic EC use.

Electronic Cigarette Use and the Risk of Cardiovascular Diseases

Electronic cigarettes or e-cigarettes are the most frequently used tobacco product among adolescents. Despite the widespread use of e-cigarettes and the known detrimental cardiac consequences of nicotine, the effects of e-cigarettes on the cardiovascular system are not well-known. Several in vitro and in vivo studies delineating the mechanisms of the impact of e-cigarettes on the cardiovascular system have been published. These include mechanisms associated with nicotine or other components of the aerosol or thermal degradation products of e-cigarettes. The increased hyperlipidemia, sympathetic dominance, endothelial dysfunction, DNA damage, and macrophage activation are prominent effects of e-cigarettes. Additionally, oxidative stress and inflammation are unifying mechanisms at many levels of the cardiovascular impairment induced by e-cigarette exposure. This review outlines the contribution of e-cigarettes in the development of cardiovascular diseases and their molecular underpinnings.

Cardiovascular Outcomes among Combustible-Tobacco and Electronic Nicotine Delivery System (ENDS) Users in Waves 1 through 5 of the Population Assessment of Tobacco and Health (PATH) Study, 2013-2019

BACKGROUND

Prior studies have not clearly established risk of cardiovascular disease (CVD) among smokers who switch to exclusive use of electronic nicotine delivery systems (ENDS). We compared cardiovascular disease incidence in combustible-tobacco users, those who transitioned to ENDS use, and those who quit tobacco with never tobacco users.

METHODS

This prospective cohort study analyzes five waves of Population Assessment of Tobacco and Health (PATH) Study data, Wave 1 (2013-2014) through Wave 5 (2018-2019). Cardiovascular disease (CVD) incidence was captured over three intervals (Waves 1 to 3, Waves 2 to 4, and Waves 3 to 5). Participants were adults (40+ years old) without a history of CVD for the first two waves of any interval. Change in tobacco use status, from exclusive past 30 day use of any combustible-tobacco product to either exclusive past 30 day ENDS use, dual past 30 day use of ENDS and combustible-tobacco, or no past 30 day use of any tobacco, between the first two waves of an interval was used to predict onset of CVD between the second and third waves in the interval. CVD incidence was defined as a new self-report of being told by a health professional that they had congestive heart failure, stroke, or a myocardial infarction. Generalized estimating equation (GEE) analyses combined 10,548 observations across intervals from 7820 eligible respondents.

RESULTS

Overall, there were 191 observations of CVD among 10,548 total observations (1.7%, standard error (SE) = 0.2), with 40 among 3014 never users of tobacco (1.5%, SE = 0.3). In multivariable models, CVD incidence was not significantly different for any tobacco user groups compared to never users. There were 126 observations of CVD among 6263 continuing exclusive combustible-tobacco users (adjusted odds ratio [AOR] = 1.44; 95% confidence interval (CI) 0.87-2.39), 15 observations of CVD among 565 who transitioned to dual use (AOR = 1.85; 0.78-4.37), and 10 observations of CVD among 654 who quit using tobacco (AOR = 1.18; 0.33-4.26). There were no observations of CVD among 53 who transitioned to exclusive ENDS use.

CONCLUSIONS

This study found no difference in CVD incidence by tobacco status over three 3 year intervals, even for tobacco quitters. It is possible that additional waves of PATH Study data, combined with information from other large longitudinal cohorts with careful tracking of ENDS use patterns may help to further clarify this relationship.

Human Bronchial Epithelial Cell Culture Models for Cigarette Smoke and Vaping Studies

Despite the continuing public health efforts to stop or reduce smoking, cigarette smoke use remains popular in the youth and adult population. A recent surge in the use of electronic cigarette and vaping products has created another major health challenge in public health. There is an urgent need to use physiologically relevant models to study the health effect of smoking or vaping in human subjects. Airway diseases such as bronchitis (Landman et al., CMAJ 191:E1321-E1331, 2019; Goniewicz, et al. Harm Reduct J 17:91, 2020; Xie et al., JAMA Netw Open 3:e2020816, 2020) have been described in people who smoke, vape, or both. Here, we will describe methods to collect, expand, and culture human airway epithelial cells from endobronchial brushings and expose these cells cultured at the air-liquid interface to cigarette smoke or electronic cigarette vapor.

Improving on estimates of the potential relative harm to health from using modern ENDS (vaping) compared to tobacco smoking

BACKGROUND

Although the harm to health from electronic nicotine delivery systems (ENDS) compared to smoked tobacco remains highly uncertain, society and governments still need to know the likely range of the relative harm to inform regulatory policies for ENDS and smoking.

METHODS

We identified biomarkers with specificity of association with different disease groupings e.g., volatile organic compound (VOCs) for chronic obstructive pulmonary disease; and tobacco-specific N´-nitrosamines (TSNAs) and polycyclic aromatic hydrocarbons (PAHs) for all cancers. We conducted a review of recent studies (post January 2017) that compared these biomarkers between people exclusively using ENDS and those exclusively smoking tobacco. The percentage differences in these biomarkers, weighted by study size and adjusted for acrolein from other sources, were used as a proxy for the assumed percentage difference in disease harm between ENDS and smoking. These relative differences were applied to previously modelled estimates of smoking-related health loss (in health-adjusted life-years; HALYs).

RESULTS

The respective relative biomarker levels (ENDS vs smoking) were: 28% for respiratory diseases (five results, three studies); 42% for cancers (five results, four studies); and 35% for cardiovascular (seven results, four studies). When integrated with the HALY impacts by disease, the overall harm to health from ENDS was estimated to be 33% that of smoking.

CONCLUSIONS

This analysis, suggests that the use of modern ENDS devices (vaping) could be a third as harmful to health as smoking in a high-income country setting. But this estimate is based on a limited number of biomarker studies and is best be considered a likely upper level of ENDS risk given potential biases in our method (i.e., the biomarkers used being correlated with more unaccounted for toxicants in smoking compared to with using ENDS).

Association between e-cigarette use and asthma: a systematic review and meta-analysis

OBJECTIVE

Increasing e-cigarette use combined with emerging evidence of their respiratory effects raises concerns about their potential impact on asthma prevalence. This review evaluates the most recent available evidence on the association of e-cigarette use and asthma world-wide.

METHODS

A literature search was performed in PubMed, Scopus, CINAHL, Cochrane Library, Web of Science and ProQuest in March 2021. This study was conducted in accordance with the guidelines of the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) registered with PROSPERO (registration number: CRD42020211812).

STUDY SELECTIONS

Cross-sectional and cohort studies assessing the association between e-cigarette use and asthma were eligible for inclusion. Studies examining exacerbations in asthma symptoms and severity were excluded. The quality of the included studies was assessed using the Appraisal tool for Cross-Sectional Studies (AXIS).

RESULTS

Thirteen cross-sectional studies with the sample size of 1,039,203 met the eligibility criteria. Odds ratios were pooled using a random effects model. Pooled analysis found a significant association between current e-cigarette use and asthma (pOR = 1.36, 95% CI 1.21-1.52) and ever e-cigarette use and asthma (pOR = 1.24 95% CI 1.13-1.36).

CONCLUSION

Our review found that e-cigarette use and ever e-cigarette use are correlated with asthma. However, heterogeneity and inconsistencies between covariates limited the interpretation of the results. This warrants further studies to investigate any potential causal association between e-cigarette use and asthma. No funding was received for this systematic review.

Electronic Cigarettes and Asthma: What Do We Know So Far?

Electronic cigarettes (EC) are a novel product, marketed as an alternative to tobacco cigarette. Its effects on human health have not been investigated widely yet, especially in specific populations such as patients with asthma. With this review, we use the existing literature in order to answer four crucial questions concerning: (1) ECs' role in the pathogenesis of asthma; (2) ECs' effects on lung function and airway inflammation in patients with asthma; (3) ECs' effects on asthma clinical characteristics in asthmatics who use it regularly; and (4) ECs' effectiveness as a smoking cessation tool in these patients. Evidence suggests that many EC compounds might contribute to the pathogenesis of asthma. Lung function seems to deteriorate by the use of EC in this population, while airway inflammation alters, with the aggravation of T-helper-type-2 (Th2) inflammation being the most prominent but not the exclusive effect. EC also seems to worsen asthma symptoms and the rate and severity of exacerbations in asthmatics who are current vapers, whilst evidence suggests that its effectiveness as a smoking cessation tool might be limited. Asthmatic patients should avoid using EC.

Respiratory and Cardiovascular Health Effects of e-Cigarette Substitution: Protocol for Two Living Systematic Reviews

Background

Despite the clear risks of tobacco use, millions of people continue to smoke. Electronic nicotine delivery systems (ENDS), commonly called e-cigarettes, have been proposed as a substitute for those who are unwilling or unable to quit. Current systematic and narrative reviews on the health effects of ENDS use, particularly respiratory and cardiovascular effects, have come to differing conclusions.

Objective

We conducted two systematic reviews to critically assess and synthesize available human studies on the respiratory and cardiovascular health effects of ENDS substitution for people who smoke. The primary goal is to provide clinicians with evidence on the health effects of ENDS substitution to inform their treatment recommendations and plans. The twin goal of the reviews is to promote health literacy in ENDS users with facts on the health effects of ENDS.

Methods

These two reviews will be living systematic reviews. The systematic reviews will be initiated through a baseline review. Studies will be evaluated using the JBI quality assessment tools and a checklist of biases drawn from the Centre for Evidence Based Medicine Catalogue of Bias. A narrative synthesis is planned because of the heterogeneity of data. A search for recently published studies will be conducted every 3 months, and an updated review will be published every 6 months for the duration of the project or possibly longer.

Results

The baseline and updated reviews will be published in a peer-reviewed journal. The findings of the reviews will be reported in a white paper for clinicians and a fact sheet for people who use ENDS.

Conclusions

The substitution of ENDS for cigarettes is one way to potentially reduce the risks of smoking. Clinicians and their patients need to understand the potential benefits and possible risks of substituting ENDS for cigarettes. Our living systematic reviews seek to highlight the best and most up-to-date evidence in this highly contentious and fast-moving field of research.

Trial Registration

PROSPERO CRD42021239094; https://www.crd.york.ac.uk/prospero/display_record.php?RecordID=239094

International Registered Report Identifier (IRRID)

DERR1-10.2196/29084