Association of Electronic Cigarette Use With Smoking Habits, Demographic Factors, and Respiratory Symptoms

The potential health effects associated with electronic-cigarette

A good old gateway theory that electronic-cigarettes (e-cigarettes) are widely recognized as safer tobacco substitutes. In actuality, demographics also show that vaping cannibalizes smoking, the best explanation of the data is the "common liability". However, the utilization of e-cigarette products remains a controversial topic at present. Currently, there has been a widespread and substantial growth in e-cigarette use worldwide owing to their endless new flavors and customizable characteristics. Furthermore, e-cigarette has grown widespread among smokers as well as non-smokers, including adolescents and young adults. And some studies have shown that e-cigarette users are at greater risk to start using combustible cigarettes while e-cigarettes use was also observed the potential benefits to people who want to quit smoking or not. Although it is true that e-cigarettes generally contain fewer toxic substances than combustible cigarettes, this does not mean that the chemical composition in e-cigarettes aerosols poses absolutely no risks. While concerns about toxic substances in e-cigarettes and their widespread use in the population are reasonable, it is also crucial to consider that e-cigarettes have been associated with the potential for promoting smoking cessation and the clinically relevant improvements in users with smoking-related pathologies. Meanwhile, there is still short of understanding of the health impacts associated with e-cigarette use. Therefore, in this review, we discussed the health impacts of e-cigarette exposure on oral, nasal, pulmonary, cardiovascular systems and brain. We aspire for this review to change people's previous perceptions of e-cigarettes and provide them with a more balanced perspective. Additionally, we suggest appropriate adjustments on regulation and policy for e-cigarette to gain greater public health benefits.

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.

Is there still a social gradient in respiratory symptoms? A population-based Nordic EpiLung-study

BACKGROUND

Respiratory symptoms are a common public health issue that can partly be attributed to preventable risk factors, such as tobacco smoking and occupational exposure, which are more common in individuals with lower socioeconomic status.

OBJECTIVE

Our aim was to evaluate the social gradient in respiratory symptoms in Nordic countries.

METHODS

This study included participants aged 30-65 years from five cross-sectional population-based questionnaire surveys in 2016 in Finland and Sweden (N = 25,423) and in 2017-2019 in Norway (N = 27,107). Occupational skill levels 1 and 2 (occupations requiring compulsory education) were combined and compared to skill levels 3 and 4 (occupations requiring upper secondary and tertiary education). Meta-analysis was conducted to obtain pooled age- and sex adjusted odds ratios (aORs) of associations between occupational skill and the respiratory symptoms including recurrent wheeze, dyspnoea, and productive cough.

RESULTS

In the meta-analysis, recurrent wheeze, dyspnoea, and productive cough showed a social gradient. The participants with occupational skill 1 and 2 had higher risk for recurrent wheeze (aOR 1.78, 95% CI 1.34-2.22) and dyspnoea (aOR 1.59, 95% CI 1.29-1.90) compared to occupational skill 3 and 4 in Sweden and Finland. Similarly increased risk was observed for combined assessment of dyspnoea and wheeze (aOR 1.05, 95% CI 1.03-1.07) in Norway. In a meta-analysis including all three countries, the aOR for productive cough was 1.31 95% CI 1.07-1.56.

CONCLUSIONS

Occupations with lower, compared to higher, skill levels were associated with an increased risk of recurrent wheeze, dyspnoea, and productive cough.

Longitudinal association between e-cigarette use and respiratory symptoms among US adults: Findings from the Population Assessment of Tobacco and Health Study Waves 4-5

BACKGROUND

We assessed longitudinal effects of e-cigarette use on respiratory symptoms in a nationally representative sample of US adults by combustible tobacco smoking status.

METHODS

We analyzed Waves 4-5 public-use data from the Population Assessment of Tobacco and Health Study. Study sample included adult respondents who reported no diagnosis of respiratory diseases at Wave 4, and completed Waves 4-5 surveys with no missing data on analytic variables (N = 15,291). Outcome was a validated index of functionally important respiratory symptoms based on 7 wheezing/cough questions (range 0-9). An index score of ≥2 was defined as having important respiratory symptoms. Weighted lagged logistic regression models were performed to examine the association between e-cigarette use status at Wave 4 (former/current vs. never use) and important respiratory symptoms at Wave 5 by combustible tobacco smoking status (i.e., never/former/current smokers), adjusting for Wave 4 respiratory symptom index, sociodemographic characteristics, secondhand smoke exposure, body mass index, and chronic disease.

RESULTS

Among current combustible tobacco smokers, e-cigarette use was associated with increased odds of reporting important respiratory symptoms (former e-cigarette use: adjusted odds ratio [AOR] = 1.39, 95% confidence interval [CI]: 1.07-1.81; current e-cigarette use: AOR = 1.55, 95% CI: 1.17-2.06). Among former combustible tobacco smokers, former e-cigarette use (AOR = 1.51, 95% CI: 1.06-2.15)-but not current e-cigarette use (AOR = 1.59, 95% CI: 0.91-2.78)-was associated with increased odds of important respiratory symptoms. Among never combustible tobacco smokers, no significant association was detected between e-cigarette use and important respiratory symptoms (former e-cigarette use: AOR = 1.62, 95% CI: 0.76-3.46; current e-cigarette use: AOR = 0.82, 95% CI: 0.27-2.56).

CONCLUSIONS

The association between e-cigarette use and respiratory symptoms varied by combustible tobacco smoking status. Current combustible tobacco smokers who use e-cigarettes have an elevated risk of respiratory impairments.

Electronic cigarette use in relation to changes in smoking status and respiratory symptoms

INTRODUCTION

How e-cigarette use relates to changes in smoking status and respiratory symptoms in the population remains controversial. The aim was to study the association between e-cigarette use and, changes in smoking status and changes in respiratory symptoms.

METHODS

A prospective, population-based study of random samples of the population (age 16-69 years) was performed within The Obstructive Lung Disease in Northern Sweden (OLIN) study and West Sweden Asthma Study (WSAS). A validated postal questionnaire containing identical questions was used in OLIN and WSAS at baseline in 2006-2008 and at follow-up in 2016. In total, 17325 participated on both occasions. Questions about respiratory symptoms and tobacco smoking were included in both surveys, while e-cigarette use was added in 2016.

RESULTS

In 2016, 1.6% used e-cigarettes, and it was significantly more common in persistent tobacco smokers (10.6%), than in those who quit smoking (2.1%), started smoking (7.8%), or had relapsed into tobacco smoking at follow-up (6.4%) (p<0.001). Among current smokers at baseline, tobacco smoking cessation was less common in e-cigarette users than e-cigarette non-users (14.2% vs 47.6%, p<0.001) and there was no association with a reduction in the number of tobacco cigarettes smoked per day. Those who were persistent smokers reported increasing respiratory symptoms. In contrast, the symptoms decreased among those who quit tobacco smoking, but there was no significant difference in respiratory symptoms between quitters with and without e-cigarette use.

CONCLUSIONS

E-cigarette use was associated with persistent tobacco smoking and reporting respiratory symptoms. We found no association between e-cigarette use and tobacco smoking cessation, reduction of number of tobacco cigarettes smoked per day or reduction of respiratory symptoms.

Sex-specific lung inflammation and mitochondrial damage in a model of electronic cigarette exposure in asthma

The prevalence of electronic cigarette (EC) use among adult with asthma has continued to increase over time, in part due to the belief of being less harmful than smoking. However, the extent of their toxicity and the involved mechanisms contributing to the deleterious impact of EC exposure on patients with preexisting asthma have not been delineated. In the present project, we tested the hypothesis that EC use contributes to respiratory damage and worsening inflammation in the lungs of patients with asthma. To define the consequences of EC exposure in established asthma, we used a mouse model with/without preexisting asthma for short-term exposure to EC aerosols. C57/BL6J mice were sensitized and challenged with a DRA (dust mite, ragweed, Aspergillus fumigates, 200 µg/mL) mixture and exposed daily to EC with nicotine (2% nicotine in 30:70 propylene glycol: vegetable glycerin) or filtered air for 2 wk. The mice were evaluated at 24 h after the final EC exposure. After EC exposure in asthmatic mice, lung inflammatory cell infiltration and goblet cell hyperplasia were increased, whereas EC alone did not cause airway inflammation. Our data also show that mitochondrial DNA (mtDNA) content and a key mtDNA regulator, mitochondrial transcription factor A (TFAM), are reduced in asthmatic EC-exposed mice in a sex-dependent manner. Together, these results indicate that TFAM loss in lung epithelium following EC contributes to male-predominant sex pathological differences, including mitochondrial damage, inflammation, and remodeling in asthmatic airways.NEW & NOTEWORTHY Respiratory immunity is dysregulated in preexisting asthma, and further perturbations by EC use could exacerbate asthma severity. However, the extent of their toxicity and the involved mechanisms contributing to the deleterious impact of EC exposure on patients with preexisting asthma have not been delineated. We found that EC has unique biological impacts in lungs and potential sex differences with loss of TFAM, a key mtDNA regulator, in lung epithelial region from our animal EC study.

Cardiopulmonary Impact of Electronic Cigarettes and Vaping Products: A Scientific Statement From the American Heart Association

Vaping and electronic cigarette (e-cigarette) use have grown exponentially in the past decade, particularly among youth and young adults. Cigarette smoking is a risk factor for both cardiovascular and pulmonary disease. Because of their more limited ingredients and the absence of combustion, e-cigarettes and vaping products are often touted as safer alternative and potential tobacco-cessation products. The outbreak of e-cigarette or vaping product use-associated lung injury in the United States in 2019, which led to >2800 hospitalizations, highlighted the risks of e-cigarettes and vaping products. Currently, all e-cigarettes are regulated as tobacco products and thus do not undergo the premarket animal and human safety studies required of a drug product or medical device. Because youth prevalence of e-cigarette and vaping product use was as high as 27.5% in high school students in 2019 in the United States, it is critical to assess the short-term and long-term health effects of these products, as well as the development of interventional and public health efforts to reduce youth use. The objectives of this scientific statement are (1) to describe and discuss e-cigarettes and vaping products use patterns among youth and adults; (2) to identify harmful and potentially harmful constituents in vaping aerosols; (3) to critically assess the molecular, animal, and clinical evidence on the acute and chronic cardiovascular and pulmonary risks of e-cigarette and vaping products use; (4) to describe the current evidence of e-cigarettes and vaping products as potential tobacco-cessation products; and (5) to summarize current public health and regulatory efforts of e-cigarettes and vaping products. It is timely, therefore, to review the short-term and especially the long-term implications of e-cigarettes and vaping products on cardiopulmonary health. Early molecular and clinical evidence suggests various acute physiological effects from electronic nicotine delivery systems, particularly those containing nicotine. Additional clinical and animal-exposure model research is critically needed as the use of these products continues to grow.

Heated Tobacco Products: Insights into Composition and Toxicity

Heated tobacco products (HTPs) are novel products that allow users to inhale nicotine by heating (350 °C) reconstituted tobacco rather than combustion (900 °C) as in conventional cigarettes. HTP sticks containing reconstituted tobacco come in various flavours such as menthol, citrus, etc., like electronic cigarette liquids. Thus, the composition of HTP aerosol will also vary according to the flavouring agents added. Overall, the content of toxic chemicals in HTP aerosol appears to be lower than in cigarette smoke. However, the concentrations of more than twenty harmful and potentially harmful constituents have been reported to be higher in HTP aerosol than in cigarette smoke. Further, several toxic compounds not detected in cigarette smoke are also reported in HTP aerosol. Thus, the risks of HTP use remain unknown. Most of the available data on the composition and health effects of mainstream HTP aerosol exposure are generated by the tobacco industry. Few independent studies have reported short-term pathophysiological effects of HTP use. Currently available HTP toxicity data are mainly on the pulmonary and cardiovascular systems. Moreover, there are no long-term toxicity data and, therefore, the claims of the tobacco industry regarding HTPs as a safer alternative to traditional combustible cigarettes are unsubstantiated. Furthermore, HTP aerosol contains the highly addictive substance nicotine, which is harmful to the adolescent brain, developing foetuses, pregnant women, and also adults. Hence, comprehensive studies addressing the safety profiling related to long-term HTP use are warranted. With this background, the following review summarizes the current state of knowledge on HTP toxicity on four broad lines: composition of mainstream HTP aerosol compared to traditional combustible cigarette smoke, biomarkers of HTP exposure, health effects of HTP exposure, and the harm reduction aspect.

Assessing tobacco use in Swedish young adults from self-report and urinary cotinine: a validation study using the BAMSE birth cohort

OBJECTIVES

Studies on health effects of tobacco often rely on self-reported exposure data, which is subjective and can lead to misclassification. The aim of this study was to describe the prevalence of cigarette smoking, snus and e-cigarette use, as well as to validate self-reported tobacco use among young adults in Sweden.

METHOD

Participants of a population-based Swedish cohort (n=3052), aged 22-25 years, assessed their tobacco use in a web questionnaire. Urinary cotinine was analysed in a subsample of the study population (n=998). The agreement between self-reported tobacco use and urinary cotinine was assessed using Cohen's Kappa coefficient (κ) at a cut-off level of 50 ng/mL.

RESULTS

Patterns of tobacco use differed between men and women. Among men, 20.0% reported daily snus use, 5.8% daily cigarette smoking and 5.6% any e-cigarette use. In contrast, 3.2% of the women reported daily snus use, 9.0% daily cigarette smoking and 2.4% any e-cigarette use. Among the tobacco use categories, daily snus users had the highest levels of cotinine. Of reported non-tobacco users, 3.5% had cotinine levels above the cut-off, compared with 68.0% among both occasional cigarette smokers and snus users, 67.5% among all e-cigarette users and 94.7% and 97.8% among daily cigarette smokers and snus users, respectively. Agreement between self-reported tobacco use and urinary cotinine was classified as strong for daily use of cigarettes (κ=0.824) and snus (κ=0.861), while moderate to weak for occasional smoking (κ=0.618), occasional snus use (κ=0.573) and any e-cigarette use (κ=0.576).

CONCLUSIONS

We found high validity of self-reported tobacco use in our study population, particularly for daily tobacco use. Further, we found that daily snus users were exposed to high levels of cotinine. Together with previous findings, our results indicate good validity of self-reported tobacco use among young adults.

Participatory research on the prevalence of Multi-Substance vaping in college students

OBJECTIVES

To assess electronic nicotine delivery system (ENDS) use and vaping behaviors and attitudes in college students.

METHODS

A student-faculty partnership administered a cross-sectional survey to undergraduate students (N = 339) in 2019.

RESULTS

49.8% of students reported using ENDS or vaping in the past 30 days. 48.9% of students who vaped reported vaping more than one substance in the past 30 days. The most commonly vaped substances were cannabis (34.9%), nicotine (26.7%), and flavor (19.2%). Reasons for initiating ENDS use were social (64.8%), for the high (40.8%), and for the flavor (32.4%). Both users and non-users believed ENDS were harmful and favored regulation.

CONCLUSIONS

Young people who use ENDS commonly vape more than one substance; a critical finding in light of the current vaping lung injury epidemic. The importance of social reasons for initiating ENDS and broad support for regulation suggest jurisdictions consider regulation to reduce ENDS use in young adults.

Interaction of smoking and social status on the risk of respiratory outcomes in a Swedish adult population: A Nordic Epilung study

BACKGROUND

Evidence abounds on the independent roles of social class and smoking in relation to obstructive airway diseases, but data are sparse on the impact of their interaction. We evaluated whether and to what extent social class and smoking interact in relation to risk of respiratory diseases in adults.

METHODS

Data from the population-based studies, West Sweden Asthma Study (WSAS, n = 23,753) and Obstructive Lung Disease in Northern Sweden studies (OLIN, n = 6519), were used, constituting randomly selected adults aged 20-75 years. Bayesian network analysis was used to estimate the probability for the interaction between smoking and socioeconomic status in relation to respiratory outcomes.

RESULTS

Occupational and educational SES modified the association between smoking and the probability of allergic and non-allergic asthma. Former smokers who were at intermediate non manual employees and manual workers in service had higher probability of allergic asthma compared to professionals and executives. Furthermore, former smokers with primary education had higher probability of non-allergic asthma than those with secondary and tertiary education. Similarly, former smokers among professionals and executives had higher probability of non-allergic asthma than manual and home workers and primary educated. Likewise, allergic asthma due to former smoking was higher among highly educated compared to low educated.

CONCLUSIONS

Beyond their independent roles, socioeconomic status and smoking interact in defining the risk of respiratory diseases. Clearer understanding of this interaction can help to identify population subgroups at most need of public health interventions.

The spread of heated tobacco product (HTP) use across various subgroups during 2015-16 and 2017-18 in Japan

BACKGROUND

Heated tobacco product (HTP) use has increased substantially between 2016 and 2017 in Japan. This study aims to clarify how HTP use (IQOS, Ploom, and glo) spread across the different combustible cigarette smoking statuses during 2015-16 and 2017-18 in Japan.

METHODS

We compared the two periods of (i) 2015 to 2016 (N = 5,366) and (ii) 2017 to 2018 (N = 3,422) from a longitudinal study randomly sampling members from the Japan "Society and New Tobacco" Internet Survey (JASTIS). Multivariable logistic regression models for current HTP use in the previous 30 days by combustible cigarette smoking status in the previous year were used adjusting for socio-demographic factors.

RESULTS

HTP use increased by 10 times in the 2017-18 cohort compared with the 2015-16 cohort according to the adjusted odds ratio (95% confidence interval) for current HTP use as 10.2 (7.03-14.8). According to smoking status, significantly higher adjusted ORs (95% CIs) of current HTP use for the after period were observed: 2.60 (1.37-4.94) for never smokers, 7.82 (3.64-16.8) for former smokers, 21.1 (5.73-77.9) for current smokers with intention to quit, and 17.0 (9.58-30.3) for current smokers without intention to quit.

CONCLUSION

During 2015 to 2018 in Japan, HTP use dramatically increased in all subgroups except for never smokers.

The E-cigarette or Vaping Product Use-Associated Lung Injury Epidemic: Pathogenesis, Management, and Future Directions: An Official American Thoracic Society Workshop Report

E-cigarette or vaping product use-associated lung injury (EVALI) is a severe pulmonary illness associated with the use of e-cigarettes or vaping products that was officially identified and named in 2019. This American Thoracic Society workshop was convened in 2021 to identify and prioritize research and regulatory needs to adequately respond to the EVALI outbreak and to prevent similar instances of disease associated with e-cigarette or vaping product use. An interdisciplinary group of 26 experts in adult and pediatric clinical care, public health, regulatory oversight, and toxicology were convened for the workshop. Four major topics were examined: 1) the public health and regulatory response to EVALI; 2) EVALI clinical care; 3) mechanisms contributing to EVALI; and 4) needed actions to address the health effects of EVALI. Oral presentations and group discussion were the primary modes used to identify top priorities for addressing EVALI. Initiatives including a national EVALI case registry and biorepository, integrated electronic medical record coding system, U.S. Food and Drug Administration regulation and enforcement of nicotine e-cigarette standards, regulatory authority over nontobacco-derived e-cigarettes, training in evaluating exogenous exposures, prospective clinical studies, standardized clinical follow-up assessments, ability to more readily study effects of cannabinoid e-cigarettes, and research to identify biomarkers of exposure and disease were identified as critical needs. These initiatives will require substantial federal investment as well as changes to regulatory policy. Overall, the workshop identified the need to address the root causes of EVALI to prevent future outbreaks. An integrated approach from multiple perspectives is required, including public health; clinical, basic, and translational research; regulators; and users of e-cigarettes. Improving the public health response to reduce the risk of another substantial disease-inducing event depends on coordinated actions to better understand the inhalational toxicity of these products, informing the public of the risks, and developing and enforcing regulatory standards for all e-cigarettes.

Electronic Cigarettes: A Narrative Review and Cohort Study of Electronic Cigarette Users in the Otolaryngology Clinic

Electronic nicotine delivery systems (ENDSs) are growing in popularity, particularly in young adults. While in vitro and murine models have demonstrated potentially harmful health effects of ENDSs, long-term health effects and clinical outcomes are generally unknown. Use as a smoking cessation aid is propagated by studies of potential harm reduction compared to conventional cigarette smoking. We present a review of the current controversies of ENDS use and present a novel cohort of patients visiting the otolaryngology clinic with known ENDS use to understand their clinical and demographic characteristics and the prevalence of otolaryngologic inflammatory diagnoses. Eighty-eight patients had 105 diagnoses. Forty-three (48.9%) ENDS users had at least 1 inflammatory diagnosis. ENDS use was more common in White, male patients between the ages of 18 and 35 years. The most common inflammatory diagnoses were chronic otitis media (17.4%) and allergic rhinitis (13.0%). While the rate of inflammatory disease was significantly higher in male than in female patients (60.7% vs 28.1% p = 0.003), no significant association was seen between inflammatory disease and age, race/ethnicity, or length of ENDS use. The identification and description of patients with ENDS use will help clinicians' better risk-stratify otolaryngologic diagnoses associated with this novel health behavior. Additionally, further clinical research is necessary to elucidate long-term health outcomes of ENDS use.

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.

The Health Effects of Real-World Dual Use of Electronic and Conventional Cigarettes versus the Health Effects of Exclusive Smoking of Conventional Cigarettes: A Systematic Review

BACKGROUND

A high prevalence of dual use of e-cigarettes and conventional cigarettes has been reported across the world.

METHODS

A systematic search was carried out. We included original articles on any topic relevant to health, excluding mental health, in all languages. The PRISMA guidelines were followed. Both reviewers independently screened and read all publications. We compared dual use with exclusive smoking of conventional cigarettes (ESCC).

RESULTS

Fifty-two publications (49 studies) were included. Thirteen papers/10 studies were prospective. There was great heterogeneity across studies. Many methodological weaknesses, such as inaccurate exposure measurement, lack of adjustment for former tobacco consumption, and lack of significance testing were identified. Most prospective studies found dual use to be at least as harmful as ESCC. The longest follow-up was six years. Most of the best available cross-sectional studies found dual use associated with the same and, in several studies, significantly higher risk of self-reported symptoms/disease than in ESCC. The intensity of cigarette smoking seems associated with worse health.

CONCLUSION

Existing studies indicate that dual use is at least as, or probably even more, harmful than ESCC. Due to the predominance of cross-sectional studies and the methodological weaknesses we judged the overall certainty of the evidence as "low certainty".

Tobacco use profiles by respiratory disorder status for adults in the wave 1-wave 4 population assessment of tobacco and health (PATH) study

•

Exclusive ENDS use is associated with a prior COPD diagnosis.

•

Dual ENDS/cigarette use is associated with prior diagnoses of COPD and bronchitis.

•

Analyses adjusted for behavioral health symptoms and other respiratory disorders.

•

Complete tobacco cessation is most beneficial in reducing respiratory complications.

Limited evidence exists on the association between electronic nicotine delivery systems (ENDS) and chronic respiratory disorders. This study examines the association of combustible tobacco and ENDS use with chronic respiratory disorders among US adults. Public-use data from the Population Assessment of Tobacco and Health (PATH) Study Wave 1 (2013–2014), Wave 2 (2014–2015), Wave 3 (2015–2016), and Wave 4 (2016–2018) were pooled. Analyses focused on adults with W1–W4 respiratory disorder data and current tobacco use at W4, as well as youth entering the adult cohort at W2 through W4 (N = 26,072). We fit weighted multivariable logistic regression models for each respiratory outcome (asthma, COPD, bronchitis) using W4 longitudinal weights. Cigarette smokers (adjusted odds ratio [AOR] = 0.8, 95 % CI 0.7–0.9) were less likely to report an asthma diagnosis (p = 0.013). In contrast, ENDS users (AOR = 6.5, 95 % CI 3.7–11.5), cigarette smokers (AOR = 6.1, 95 % CI 4.0–9.1), dual users of cigarettes and ENDS (AOR = 5.4, 95 % CI 3.4–8.7), current users of non-cigarette combustible, smokeless, and polytobacco products (AOR = 4.4, 95 % CI 3.1–6.4), and former users of any product (AOR = 3.0, 95 % CI 1.9–4.7) had significantly elevated odds of reporting a diagnosis of COPD (p < 0.001). Similar patterns to COPD were observed for bronchitis (p < 0.001). Current and former tobacco use, including ENDS, were significantly associated with prevalence of self-reported COPD and bronchitis after controlling for demographic and psychosocial confounders.

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.

Transitions between tobacco products: Correlates of changes in cigarette smoking and e-cigarette use among exclusive adult smokers and dual users in Mexico

This study examined transitions in tobacco products use among Mexican smokers and dual users. Data were analyzed from exclusive smokers (n = 2,946) and dual users (n = 1,643) recruited from an online consumer research panel and surveyed every-four months from November 2018 to April 2021. For exclusive smokers, estimated transitions were (time "t + 1" four months after prior survey): a) remain as exclusive smokers; b) dual use; c) exclusive e-cigarette use or quit both products. Among dual users, transitions analyzed were: a) remain as dual user; b) exclusive smoker; c) exclusive e-cigarette user or quit both products. Multinomial models regressed transitions at "t + 1" on time "t" for control variables. Most exclusive smokers (81%) remained as such, 12.6% transitioned to dual use, 2.3% to exclusive e-cigarette use, and 4% quitted both products. Exclusive smokers were more likely to transition to dual use if they recently attempted to quit (AOR = 1.45) or had partners/family or friends who used e-cigarettes (AOR = 2.47 & 2.56 respectively). Most dual users (74.8%) remained as dual users, 20.4% transitioned to exclusive smoking, 1.6% transitioned to exclusive e-cigarette use, and 3.2% quitted both products. Dual users were more likely to transition to exclusive smoking if they had lower educational attainment, recently attempted to quit e-cigarettes (AOR = 1.70). Having friends who use e-cigarettes (AOR = 0.29) and higher smoking dependence (AOR = 0.55) were associated with a lower likelihood of quitting. Recent quit attempts and e-cigarette use among close social network members may explain the short-term transitions, though longer follow-up is needed to assess sustained smoking cessation.

The Influence of Mental Health and Respiratory Symptoms on the Association Between Chronic Lung Disease and E-Cigarette Use in Adults in the United States

BACKGROUND

Adults with chronic lung disease use electronic cigarettes (e-cigarette) at higher rates than those without chronic lung disease. Because e-cigarettes have now been shown to cause adverse pulmonary effects and impair immune responses, it is particularly important to identify the factors that contribute to e-cigarette use in individuals with chronic lung disease. We tested whether mental health explains the association between chronic lung disease and e-cigarette use, and whether the association between chronic lung disease and e-cigarette use is conditional on the presence of respiratory symptoms.

METHODS

Data were obtained from the 2018 Behavioral Risk Factor Surveillance System. Logistic regression was used to test the association between chronic lung disease status and e-cigarette use when controlling for demographic variables and comorbidities. Structural equation modeling was then used to evaluate (a) whether the number of bad mental health days in the past 30 days explained the association between chronic lung disease and e-cigarette use, and (b) if respiratory symptoms moderated the association between chronic lung disease and e-cigarette use.

RESULTS

The prevalence of lifetime and current e-cigarette use was significantly higher in those with than in those without chronic lung disease, as was the number of bad mental health days in the past 30 days. Mediation analysis indicated a statistically significant indirect effect of chronic lung disease on the likelihood of e-cigarette use (lifetime and current) through mental health. However, our analyses did not indicate a statistically significant interaction between chronic lung disease and respiratory symptoms in the likelihood of e-cigarette use.

CONCLUSIONS

The association between chronic lung disease and e-cigarette use may be due, in part, to poorer mental health among individuals with chronic lung disease. These findings provide preliminary evidence that improving the mental health of individuals with chronic lung disease could reduce e-cigarette use in this vulnerable population.

Alpha7 nicotinic acetylcholine receptor mediates chronic nicotine inhalation-induced cardiopulmonary dysfunction

Cigarette smoking remains the leading modifiable risk factor for cardiopulmonary diseases; however, the effects of nicotine alone on cardiopulmonary function remain largely unknown. Previously, we have shown that chronic nicotine vapor inhalation in mice leads to the development of pulmonary hypertension (PH) with right ventricular (RV) remodeling. The present study aims to further examine the cardiopulmonary effects of nicotine and the role of the α7 nicotinic acetylcholine receptor (α7-nAChR), which is widely expressed in the cardiovascular system. Wild-type (WT) and α7-nAChR knockout (α7-nAChR-/-) mice were exposed to room air (control) or nicotine vapor daily for 12 weeks. Consistent with our previous study, echocardiography and RV catheterization reveal that male WT mice developed increased RV systolic pressure with RV hypertrophy and dilatation following 12-week nicotine vapor exposure; in contrast, these changes were not observed in male α7-nAChR-/- mice. In addition, chronic nicotine inhalation failed to induce PH and RV remodeling in female mice regardless of genotype. The effects of nicotine on the vasculature were further examined in male mice. Our results show that chronic nicotine inhalation led to impaired acetylcholine-mediated vasodilatory response in both thoracic aortas and pulmonary arteries, and these effects were accompanied by altered endothelial nitric oxide synthase phosphorylation (enhanced inhibitory phosphorylation at threonine 495) and reduced plasma nitrite levels in WT but not α7-nAChR-/- mice. Finally, RNA sequencing revealed up-regulation of multiple inflammatory pathways in thoracic aortas from WT but not α7-nAChR-/- mice. We conclude that the α7-nAChR mediates chronic nicotine inhalation-induced PH, RV remodeling and vascular dysfunction.

Chronic obstructive pulmonary disease

Chronic obstructive pulmonary disease (COPD) is a major cause of morbidity, mortality, and health-care use worldwide. COPD is caused by exposure to inhaled noxious particles, notably tobacco smoke and pollutants. However, the broad range of factors that increase the risk of development and progression of COPD throughout the life course are increasingly being recognised. Innovations in omics and imaging techniques have provided greater insight into disease pathobiology, which might result in advances in COPD prevention, diagnosis, and treatment. Although few novel treatments have been approved for COPD in the past 5 years, advances have been made in targeting existing therapies to specific subpopulations using new biomarker-based strategies. Additionally, COVID-19 has undeniably affected individuals with COPD, who are not only at higher risk for severe disease manifestations than healthy individuals but also negatively affected by interruptions in health-care delivery and social isolation. This Seminar reviews COPD with an emphasis on recent advances in epidemiology, pathophysiology, imaging, diagnosis, and treatment.

Predictors of electronic cigarette use and its association with respiratory health and obesity in young adulthood in Sweden; findings from the population-based birth cohort BAMSE

Despite the growing popularity of electronic cigarettes (e-cigarettes) over the last decade, few epidemiological studies have examined the influence on respiratory health in young adulthood. The aim of this study was to identify factors associated with e-cigarette use in young adulthood in Sweden, and to examine associations between e-cigarette use and lung function, respiratory symptoms, and obesity. This cross-sectional study included 3055 young adults from Sweden and used questionnaire and clinical data obtained at age 22-25 years. The prevalence of current e-cigarette use was 3.9% (n = 120). Few participants reported daily (0.4%) or exclusive (0.8%) use of e-cigarettes. In a multivariable adjusted logistic regression model, e-cigarette use was significantly associated with male gender (OR:3.2; 95% CI:1.5-6.7) and cigarette smoking (OR:14.7; 95% CI:5.5-39.0 for daily smoking). Prevalence of cough (15.0% vs. 8.5%) and mucus production (22.3% vs. 14.8%) was significantly higher among e-cigarette users compared to non-users, while no difference in lung function was observed. In addition, the prevalence of overweight/obesity was higher among e-cigarette users compared to non-users (36.7% vs. 22.3% with BMI≥25 kg/m²). In conclusion, cigarette smokers and males used e-cigarette more often compared to females and non-cigarette smokers. Attention should be given to respiratory symptoms among e-cigarette users, although our results may be explained by the concurrent use of conventional cigarettes, as the group of exclusive e-cigarette users were too small to allow firm conclusions.

Documento de posicionamiento de la Sociedad Española de Neumología y Cirugía Torácica (SEPAR) ante las estrategias de reducción del daño del tabaco

In the last decade, the appearance of electronic cigarettes and new tobacco products (heated tobacco or smokeless tobacco) has generated a growing interest in harm reduction methods that are defined as mechanisms that seek to reduce the harmful consequences of tobacco without give up the pleasant effects of it by replacing it with these new electronic devices. However, these products are addictive and not safe as they contain nicotine. Harm reduction is a false solution as it represents a commercial strategy of the tobacco industry to increase its sales, making it difficult to control smoking, since it keeps smokers from consuming tobacco and prevents them from making serious attempts to quit. In addition, these products are a gateway to adolescents in tobacco.

Electronic Nicotine Product Cessation and Cigarette Smoking: Analysis of Waves 3 and 4 From the PATH Study

INTRODUCTION

Identifying predictors of electronic nicotine product (ENP) cessation can inform ENP cessation interventions. High rates of cooccurring ENP and cigarette (dual) use and transitions between these products underscore the importance of considering cigarette smoking status when assessing and addressing ENP cessation.

AIMS AND METHODS

We analyzed waves 3 (W3) and 4 (W4) of the Population Assessment of Tobacco and Health (PATH) study to identify (1) W3 socio-demographics, tobacco and ENP use characteristics, and psychosocial correlates of W3 cigarette smoking status (non-smoker, former, and current) among W3 adult ENP users, and (2) W3 predictors of W4 combined ENP and cigarette smoking abstinence relative to use of one or both products.

RESULTS

At W3, 65.6% of ENP users concurrently smoked cigarettes. Adjusted multinomial regression results indicated that different W3 socio-demographics, tobacco and ENP use characteristics, and psychosocial correlates were significantly associated with distinct W3 cigarette use profiles. At W4, 9.9% of individuals were abstinent from both products. These individuals were less likely to: (1) be current smokers (vs. non-smokers) or be advised to quit using tobacco, compared with cigarette only or dual users, and (2) use ENPs daily or live in a household allowing ENP use, compared with ENP only or dual users (p < .05).

CONCLUSIONS

ENP cessation approaches need to be tailored to the distinct cigarette use profiles of ENP users. Dual users and daily ENP users may require more intensive interventions to achieve the cessation of both products. Supportive physical environments, such as home vape-free policies, may facilitate ENP cessation.

IMPLICATIONS

This analysis contributes to advancing the nascent literature on predictors of electronic nicotine product (ENP) cessation, which can guide the development of ENP cessation interventions by indicating which populations, psychosocial and environmental constructs, and cooccurring behaviors interventions should target. This research also highlights the importance of considering cigarette smoking status when designing ENP cessation interventions and defining intervention outcomes.

"When I Don't Have a Cigarette It's Helpful, but It Really Don't Satisfy:" Qualitative Study of Electronic Nicotine Delivery Systems (ENDS) Use among Low-Income Smokers

BACKGROUND

Little is known about the use of electronic nicotine delivery systems (ENDS) among low-income adult cigarette smokers, who experience severe tobacco-related health disparities.

METHODS

This study conducted interviews to examine experiences and perceptions associated with ENDS use among predominantly low-income adult smokers (n = 30; mean age 30.2 ± 12.9; 60% male, 46.7% African American, 30% white, 10% more than one race; 76.7% annual household income ≤USD 24,000). Interviews were transcribed verbatim and coded in NVivo 11.

RESULTS

Overall, participants reported complementing rather than substituting their smoking with ENDS use (e.g., using ENDS only when smoking is not allowed). Predominant reasons for vaping were convenience, smoking reduction/cessation, stress management, social acceptability, lower long-term costs than smoking, and appealing flavors. Common reasons for not switching to exclusive vaping were that ENDS did not satisfy cigarette cravings and concerns about ENDS health effects. Participants indicated higher likelihood of switching to exclusive ENDS use if the products were more affordable, perceived as substantially less harmful, tasted and felt more like smoking a cigarette, and more effective for reducing cravings.

CONCLUSIONS

Continued research is needed to maximize any harm reduction potential of ENDS and ensure that these products do not contribute to worsening health disparities.

Neurobiological Mechanisms of Nicotine Reward and Aversion

Neuronal nicotinic acetylcholine receptors (nAChRs) regulate the rewarding actions of nicotine contained in tobacco that establish and maintain the smoking habit. nAChRs also regulate the aversive properties of nicotine, sensitivity to which decreases tobacco use and protects against tobacco use disorder. These opposing behavioral actions of nicotine reflect nAChR expression in brain reward and aversion circuits. nAChRs containing α4 and β2 subunits are responsible for the high-affinity nicotine binding sites in the brain and are densely expressed by reward-relevant neurons, most notably dopaminergic, GABAergic, and glutamatergic neurons in the ventral tegmental area. High-affinity nAChRs can incorporate additional subunits, including β3, α6, or α5 subunits, with the resulting nAChR subtypes playing discrete and dissociable roles in the stimulatory actions of nicotine on brain dopamine transmission. nAChRs in brain dopamine circuits also participate in aversive reactions to nicotine and the negative affective state experienced during nicotine withdrawal. nAChRs containing α3 and β4 subunits are responsible for the low-affinity nicotine binding sites in the brain and are enriched in brain sites involved in aversion, including the medial habenula, interpeduncular nucleus, and nucleus of the solitary tract, brain sites in which α5 nAChR subunits are also expressed. These aversion-related brain sites regulate nicotine avoidance behaviors, and genetic variation that modifies the function of nAChRs in these sites increases vulnerability to tobacco dependence and smoking-related diseases. Here, we review the molecular, cellular, and circuit-level mechanisms through which nicotine elicits reward and aversion and the adaptations in these processes that drive the development of nicotine dependence. SIGNIFICANCE STATEMENT: Tobacco use disorder in the form of habitual cigarette smoking or regular use of other tobacco-related products is a major cause of death and disease worldwide. This article reviews the actions of nicotine in the brain that contribute to tobacco use disorder.

E-cigarette use and adverse respiratory symptoms among adolescents and Young adults in the United States

E-cigarette use among adolescents and young adults has been associated with adverse respiratory symptoms, including symptoms of asthma and bronchitis. This investigation examined whether such associations differ by primary type of e-cigarette device used. This cross-sectional study included data from four study populations in California and Connecticut, United States, ages 13-21 years (N = 10,483), who self-reported their tobacco use behaviors and health status from 2018 to 2020. Adverse respiratory symptoms were grouped as bronchitis, asthma exacerbation, and shortness of breath. Associations with e-cigarette use were examined by frequency of e-cigarette use (regardless of device type) and most-frequently use device type in the past 30 days (pod, pen/tank, disposable, or mod). Multivariable modeling accounted for demographic variables and use of other tobacco and cannabis. Results were pooled at the study level via random-effects meta-analysis. Across the four studies, e-cigarette use >5 days/month versus never use was associated with bronchitic symptoms (summary odds ratio, sOR: 1.56; 95% confidence interval, CI: 1.37, 1.77) and shortness of breath (sOR: 1.68; 95% CI: 1.35, 2.08) but not statistically significantly with asthma exacerbations (sOR: 1.36; 95% CI; 0.95, 1.95). Among past 30-day e-cigarette users, associations with respiratory symptoms did not differ by device type. In these populations, e-cigarette use was positively associated with symptoms of bronchitis and shortness of breath, but adjusted odds of symptoms did not differ meaningfully by device type. These findings suggest that risk of these respiratory outcomes is elevated among more frequent e-cigarette users regardless of device type used.

Electronic cigarette use in 12 European countries. Results from the TackSHS survey

BACKGROUND

Limited data on electronic cigarette prevalence, patterns and settings of use are available from several European countries.

METHODS

Within the TackSHS project, a face-to-face survey was conducted in 2017-2018 in 12 European countries (Bulgaria, England, France, Germany, Greece, Ireland, Italy, Latvia, Poland, Portugal, Romania and Spain). Overall, 11,876 participants, representative of the population aged ≥15 years in each country, provided information on electronic cigarette.

RESULTS

2.4% (95% confidence interval, CI: 2.2-2.7) of the subjects (2.5% among men and 2.4% among women; 0.4% among never, 4.4% among current- and 6.5% among ex-smokers) reported current use of electronic cigarette, ranging from 0.6% in Spain to 7.2% in England. Of the 272 electronic cigarette users, 52.6% were dual users (i.e., users of both electronic and conventional cigarettes) and 58.8% used liquids with nicotine. In all, 65.1% reported using electronic cigarette in at least one indoor setting where smoking is forbidden, in particular in workplaces (34.9%), and bars and restaurants (41.5%). Multivariable logistic regression analysis showed that electronic cigarette use was lower among older individuals (p for trend <0.001) and higher among individuals with high level of education (p for trend 0.040). Participants from countries with higher tobacco cigarette prices more frequently reported electronic cigarette use (odds ratio 3.62; 95% CI: 1.80-7.30).

CONCLUSIONS

Considering the whole adult population of these 12 European countries, more than 8.3 million people use electronic cigarettes. The majority of users also smoked conventional cigarettes, used electronic cigarettes with nicotine and consumed electronic cigarettes in smoke-free indoor areas.

Impact of electronic cigarette ever use on lung function in adults aged 45-85: a cross-sectional analysis from the Canadian Longitudinal Study on Aging

OBJECTIVE

To describe the sociodemographic characteristics associated with e-cigarette ever use and to examine the impact of e-cigarette ever use on lung function impairment in an ageing population.

DESIGN

A cross-sectional analysis of data from the Canadian Longitudinal Study on Aging.

SETTING

A national stratified sample of 44 817 adults living in Canadian provinces.

PARTICIPANTS

Respondents included participants aged 45-85 and residing in the community in Canadian provinces.

OUTCOME MEASURES

The Global Lung Function Initiative normative values for forced expiratory volume in the first second (FEV₁), forced vital capacity (FVC), forced expiratory ratio (FEV₁/FVC) appropriate for age, sex, height and ethnicity were used to interpret the severity of lung function impairment. Multinomial logistic regression analysis was used to examine the impact of e-cigarette ever use on obstructive and restrictive lung function impairment.

RESULTS

The prevalence of e-cigarette ever use was 6.5% and varied by sociodemographic factors including higher prevalence among individuals younger than 65 years, those with lower education attainment and those with lower annual household income. E-cigarette ever use was associated with 2.10 (95% CI 1.57 to 2.08) times higher odds of obstructive lung function impairment after adjusting for conventional cigarette smoking and other covariates. Individuals with exposure to e-cigarette ever use and 15 or more pack-years had 7.43 (95% CI 5.30 to 10.38) times higher odds for obstructive lung function impairment when compared with non-smokers and non-e-cigarette users after adjusting for covariates. Smokers with 15 or more pack-years had higher odds of restrictive lung function impairment irrespective of e-cigarette ever use.

CONCLUSIONS

Ever use of e-cigarettes was found to be associated with obstructive lung function impairment after adjusting for covariates, suggesting that e-cigarette use may be adding to the respiratory and other chronic disease burden in the population.

Association of Vaping and Respiratory Health among Youth in the Population Assessment of Tobacco and Health (PATH) Study Wave 3

The purpose of this study is to evaluate the association of electronic nicotine product (ENP) use and its respiratory manifestations in a nationally representative sample of adolescents in the US. Cross-sectional evidence from 9750 adolescents in wave 3 (October 2015-October 2016) of the Population Assessment of Tobacco and Health (PATH) survey was used. Adjusting for demographics, lifetime number of cigarettes and cigars used, home rules about tobacco use, and tobacco used by other household members, we used logistic regression models to examine associations between ENP use and its respiratory manifestations in the past year. Among 9750 adolescents, 12% (n = 1105) used ENP in the past year. Compared to non-users, past-year ENP-users had 37% higher odds of wheezing in general (Adjusted Odds Ratio (AOR) = 1.37, 95% Confidence interval (CI): 1.11-1.71, p = 0.005) and higher odds of wheezing 4-12 times or >12 times per year versus no wheezing (AOR = 1.57, 95% CI: 1.01-2.46, p = 0.05 and AOR = 2.58, 95% CI: 1.04-6.41, p = 0.04, respectively). Additionally, odds of dry cough at night were 23% higher among ENP-users than among non-users (AOR = 1.23, 95% CI: 1.04-1.46, p = 0.02). There was no association between past-year ENP use and exercise-induced wheezing or asthma diagnosis. Among those with asthma, there was no evidence of an association between ENP use and long-acting inhaler or quick-relief inhaler use. ENP use among adolescents is associated with increased frequency of wheezing and dry cough. Early recognition of pulmonary clinical manifestations among young ENP users should be critical considerations in regulatory and prevention efforts to protect public health, and clinical efforts to prevent progression to serious pulmonary complications.

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.

Prospective association between use of electronic cigarettes and use of conventional cigarettes: a systematic review and meta-analysis

Objective

The aim of this systematic review and meta-analysis was to assess the association between e-cigarette use and subsequent initiation or recurrence of cigarette smoking.

Data sources

A systematic literature search was finalised on 11 November 2019 using PubMed (including MEDLINE), EMBASE, Cochrane Library, Scopus, PubMed Health, NICE Evidence Search, PROSPERO, CRD and PsycInfo.

Study selection

Studies were included if meeting the following criteria: reporting empirical results; longitudinal observational design with a minimum of 3 months of follow-up; including general population samples; allowing for the comparison between users and nonusers of e-cigarettes. Studies rated as having high risk of bias were excluded. Studies were independently assessed by at least two authors. The procedures described by PRISMA were followed, and the quality of evidence was rated using GRADE.

Data synthesis

30 longitudinal studies from 22 different cohorts assessing e-cigarette use among nonsmokers or never-smokers at baseline, and subsequent use of cigarette smoking at follow-up, were included in this review. A random-effects meta-analysis based on 89 076 participants showed a pooled unadjusted odds ratio (OR) of cigarette smoking among baseline nonsmoker e-cigarette users compared with nonusers of 4.68 (CI 3.64–6.02), while the adjusted OR was 3.37 (CI 2.68–4.24). These results were consistent irrespective of whether the outcome was measured as ever-smoking or as past 30-day smoking. The evidence was graded as moderate.

Conclusions

Use of e-cigarettes may predict the initiation or recurrence of cigarette smoking.

This meta-analysis shows that e-cigarette use increases the risk of future initiation or recurrence of cigarette smoking, even after adjusting for potential confounders, suggesting that e-cigarette use could be considered a predictor of subsequent smokinghttps://bit.ly/3buMccm

Asthma increased in young adults from 2008-2016 despite stable allergic rhinitis and reduced smoking

BACKGROUND

Studies have produced inconsistent results on prevalence trends in asthma and allergic rhinitis (AR). We surveyed young adults about asthma in 2008 and 2016 and examined the impact of gender, AR and smoking.

METHODS

Thirty-thousand randomly selected subjects aged 16-75 years in Western Sweden received postal questionnaires in 2008 and 50,000 in 2016. This study is based on responders aged 16-25 years, 2,143 in 2008 and 2,484 in 2016.

RESULTS

From 2008-2016 current asthma increased from 9.3% to 11.5% (p = 0.014) and was significant in males without AR (aOR 1.83, 95% CI 1.09-3.07) and male smokers (aOR 3.02, 95% CI 1.12-8.13). In both years the risk of current asthma was reduced by growing up on a farm (aOR 0.26, 95% CI 0.81-0.84 and aOR 0.47, 95% CI 0.23-0.996), independent of a family history of asthma or allergy. AR did not differ significantly from 2008-2016 (22.5% vs 24.4%, p = 0.144). Current smoking decreased from 20.3% to 15.2% (p<0.001), especially in females (23.5% to 16.2%, p<0.001). Female smokers started smoking later and smoked fewer cigarettes in 2016 than 2008. In 2016, 4.8% of the cohort reported using electronic cigarettes. Of those, 60.7% also smoked tobacco and more than two-thirds who used both (67.2%) were heavy smokers.

CONCLUSION

Current asthma increased in respondents aged 16-25 from 2008-2016, mainly among males without AR and male smokers. Current AR levelled off in this young population, while current smoking decreased among females.

Cigarette Smoke Exposure, Pediatric Lung Disease, and COVID-19

The detrimental effects of tobacco exposure on children's health are well known. Nonetheless, the prevalence of secondhand or direct cigarette smoke exposure (CSE) in the pediatric population has not significantly decreased over time. On the contrary, the rapid incline in use of e-cigarettes among adolescents has evoked public health concerns since increasing cases of vaping-induced acute lung injury have highlighted the potential harm of these new "smoking" devices. Two pediatric populations are especially vulnerable to the detrimental effects of cigarette smoke. The first group is former premature infants whose risk is elevated both due to their prematurity as well as other risk factors such as oxygen and mechanical ventilation to which they are disproportionately exposed. The second group is children and adolescents with chronic respiratory diseases, in particular asthma and other wheezing disorders. Coronavirus disease 2019 (COVID-19) is a spectrum of diseases caused by infection with the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) that has spread worldwide over the last year. Here, respiratory symptoms ranging from mild to acute respiratory distress syndrome (ARDS) are at the forefront of COVID-19 cases among adults, and cigarette smoking is associated with worse outcomes in this population, and cigarette smoking is associated with worse outcomes in this population. Interestingly, SARS-CoV-2 infection affects children differently in regard to infection susceptibility, disease manifestations, and complications. Although children carry and transmit the virus, the likelihood of symptomatic infection is low, and the rates of hospitalization and death are even lower when compared to the adult population. However, multisystem inflammatory syndrome is recognized as a serious consequence of SARS-CoV-2 infection in the pediatric population. In addition, recent data demonstrate specific clinical patterns in children infected with SARS-CoV-2 who develop multisystem inflammatory syndrome vs. severe COVID-19. In this review, we highlight the pulmonary effects of CSE in vulnerable pediatric populations in the context of the ongoing SARS-CoV-2 pandemic.

Differential responses to e-cig generated aerosols from humectants and different forms of nicotine in epithelial cells from nonsmokers and smokers

In the United States, millions of adults use electronic cigarettes (e-cigs), and a majority of these users are former or current cigarette smokers. It is unclear, whether prior smoking status affects biological responses induced by e-cigs. In this study, differentiated human nasal epithelial cells (hNECs) from nonsmokers and smokers at air-liquid interface were acutely exposed to the e-cig generated aerosols of humectants, propylene glycol (PG), and glycerol (GLY). Mucin levels were examined in the apical washes, and cytokine levels were assessed in the basolateral supernatants 24 h postexposure. The aerosol from the GLY exposure increased mucin 5, subtype AC (MUC5AC) levels in the apical wash of hNECs from nonsmokers, but not smokers. However, the aerosol from GLY induced pro-inflammatory responses in hNECs from smokers. We also exposed hNECs from nonsmokers and smokers to e-cig generated aerosol from PG:GLY with freebase nicotine or nicotine salt. The PG:GLY with freebase nicotine exposure increased MUC5AC and mucin 5, subtype B (MUC5B) levels in hNECs from nonsmokers, but the nicotine salt exposure did not. The PG:GLY with nicotine salt exposure increased pro-inflammatory cytokines in hNECs from smokers, which was not seen with the freebase nicotine exposure. Taken together, these data indicate that the e-cig generated aerosols from the humectants, mostly GLY, and the type of nicotine used cause differential effects in airway epithelial cells from nonsmokers and smokers. As e-cig use is increasing, it is important to understand that the biological effects of e-cig use are likely dependent on prior cigarette smoke exposure.

E-cigarette users are associated with asthma disease: A meta-analysis

BACKGROUND

At present, there are more than 300 million asthma patients in the world. Electronic cigarettes (e-cigarettes) are considered as a new way of smoking and are loved by young people. The relationship between e-cigarettes and asthma risk is still controversial. Therefore, we conducted a meta-analysis to explore the relationship between e-cigarettes and asthma.

METHODS

We searched PubMed, Embase, and Web of Science for research results published before august 2020. All data analysis was through R version 3.6.3. Publication bias was assessed using funnel plots, Begg's rank correlation test, and Egger regression asymmetry tests. Most of the included studies were adjusted for potential confounding factors.

RESULTS

This meta found the association of e-cigarette use with asthma, and the combined OR value was 1.27 (95% CI = 1.17-1.37). We found the significant association of current e-cigarette usage with asthma (OR = 1.30, 95% CI = 1.17-1.45), and the former use of e-cigarettes also had an association with asthma (OR = 1.22, 95% CI = 1.08-1.39). Then, when e-cigarettes were used in combination with traditional cigarettes, the association odds with asthma was 1.47 (95% CI = 1.13-1.91), which was higher than that of users who used traditional cigarettes (OR = 1.33, 95% CI = 1.19-1.49). In subgroup analysis, adult and female e-cigarette users were more closely associated with asthma.

CONCLUSION

In short, in this meta-analysis, we found that current or former use of e-cigarettes are associated with the prevalence of asthma. However, the specific relationship required more rigorous design for further verification.

Cross-Sectional Associations of Smoking and E-cigarette Use with Self-Reported Diagnosed Hypertension: Findings from Wave 3 of the Population Assessment of Tobacco and Health Study

Following their introduction a decade ago, electronic cigarettes (e-cigarettes) have grown in popularity. Given their novelty, knowledge of the health consequences of e-cigarette use remains limited. Epidemiologic studies have not comprehensively explored associations between e-cigarette use and hypertension, a highly prevalent health condition and major contributor to cardiovascular disease burden. In this study, cross-sectional associations of cigarette smoking and e-cigarette use (vaping) with self-reported diagnosed hypertension were evaluated among 19,147 18-55 year old respondents in Wave 3 (2015-2016) of the Population Assessment of Tobacco and Health Study. Multivariable analyses first modeled smoking and vaping as separate 2-category variables, then as a 6-category composite variable accounting for former smoking. After adjusting for potential confounders, current vaping (aOR = 1.31; 95%CI: 1.05-1.63) and current smoking (aOR = 1.27; 95%CI: 1.10-1.47) were both associated with higher odds of hypertension. In analyses modeling smoking and vaping compositely, respondents who were concurrently smoking and vaping had the highest odds of hypertension (aOR = 1.77; 95%CI: 1.32-2.39 [referent: never smokers]). These results differ somewhat from prior epidemiologic studies of vaping and respiratory outcomes, which consistently report smaller point estimates for current vaping than for current smoking. Our findings reinforce the uncertainty surrounding long-term health consequences of vaping, as well as highlight important distinctions between respiratory and cardiovascular outcomes when considering the harm reduction potential of e-cigarettes.

Assessment of chronic bronchitis and risk factors in young adults: results from BAMSE

Background

Chronic bronchitis is associated with substantial morbidity among elderly adults, but little is known about its prevalence and risk factors in young adults. Our aim was to assess the prevalence and early-life risk factors for chronic bronchitis in young adults.

Methods

Questionnaire data and clinical measures from the 24-year follow-up of the Swedish BAMSE (Child (Barn), Allergy, Milieu, Stockholm, Epidemiological) cohort were used. We assessed chronic bronchitis (CB) as the combination of cough and mucus production in the morning during winter. Environmental and clinical data from birth and onwards were used for analyses of risk factors.

Results

At the 24-year follow-up, 75% (n=3064) participants completed the questionnaire and 2030 performed spirometry. The overall prevalence of CB was 5.5% (n=158) with similar estimates in males and females. 49% of CB cases experienced more than three self-reported respiratory infections in the past year compared to 18% in non-CB subjects (p<0.001), and 37% of cases were current smokers (versus 19% of non-CB cases). Statistically significant lower post-bronchodilator forced expiratory volume in 1 s/forced vital capacity were observed in CB compared to non-CB subjects (mean z-score −0.06 versus 0.13, p=0.027). Daily smoking (adjusted (a)OR 3.85, p<0.001), air pollution exposure (black carbon at ages 1–4 years aOR 1.71 per 1 μg·m⁻³ increase, p=0.009) and exclusive breastfeeding for ≤4 months (aOR 0.66, p=0.044) were associated with CB.

Conclusion

Chronic bronchitis in young adults is associated with recurrent respiratory infections. Besides smoking, our results support the role of early-life exposures, such as air pollution and exclusive breastfeeding, for respiratory health later in life.

Chronic bronchitis in young adults is strongly associated with recurrent respiratory infections. Besides smoking, our results support the role of early-life environmental exposures for respiratory health in this age group.https://bit.ly/2RNsv5z

Pulmonary Health Effects of Electronic Cigarettes: A Scoping Review

BACKGROUND

There is global concern regarding the public health impact of electronic cigarettes (ECs). ECs are commonly promoted as safer than conventional cigarettes (CCs), however there is limited knowledge of the long-term health effects. This scoping review examined the pulmonary health effects of ECs reported in the literature from 2009 to 2019.

METHOD

PubMed, CINAHL, and Science Direct databases were used. Search terms included "vaping, electronic nicotine delivery systems, electronic cigarettes, lung diseases, respiratory diseases, and pulmonary." Original research articles in English that used human subjects between January 1, 2009 and January 31, 2020 and reported pulmonary outcomes were included.

RESULTS

Forty-five studies met the inclusion criteria. There were 14 (31.1%) randomized experimental, 7 (15.6%) nonrandomized experimental, 6 (13.3%) cohort, and 18 (40.0%) cross-sectional studies. Sixteen (35.6%) studies were conducted in the United States; the rest were conducted across 11 other countries. The total number of subjects was 1,465,292 and ages ranged from 12 to 99 years across studies. Eligible studies demonstrated an association between EC use and pulmonary symptoms, asthma and chronic obstructive pulmonary disease diagnosis and exacerbations. The degree of this association varied based on the use of additional tobacco products. EC use resulted in worse outcomes than nonsmoking, but resulted in improved outcomes when compared with CC use or dual use of CC and EC.

CONCLUSION

Evidence indicates that EC use, especially dual use, leads to negative pulmonary effects and adverse outcomes. Education on the potential risks and publishing of EC ingredients on labels could help improve public health safety communication and reduce EC use.

E-cigarettes and vaping - a panacea or a bane to smoking in current times?

OBJECTIVE

Use of electronic cigarettes has increased across the world in the last decade with heavy investment from the tobacco industry targeting younger population through well-designed marketing campaigns portraying e-cigarettes as harmless, less addictive and effective in smoking cessation while delivering higher nicotine concentration. The safety profile of e-cigarettes is reviewed in this paper.

CONCLUSIONS

The safety of e-cigarettes and the chemicals they contain have not been evaluated rigorously. Emerging data suggest e-cigarette use could do severe harm. People with serious mental illness, already the highest nicotine consumers, could be exploited by the tobacco industry.

E-cigarette use and respiratory disorders: an integrative review of converging evidence from epidemiological and laboratory studies

Background

Use of electronic cigarettes (e-cigarettes) is prevalent among adolescents and young adults, but there has been limited knowledge about health consequences in human populations. We conduct a systematic review and meta-analysis of results on respiratory disorders from studies of general-population samples and consider the mapping of these results to findings about biological processes linked to e-cigarettes in controlled laboratory studies.

Method

We conducted a literature search and meta-analysis of epidemiological studies on the association of e-cigarette use with asthma and with COPD. We discuss findings from laboratory studies about effects of e-cigarettes on four biological processes: cytotoxicity, oxidative stress/inflammation, susceptibility to infection and genetic expression.

Results

Epidemiological studies, both cross-sectional and longitudinal, show a significant association of e-cigarette use with asthma and COPD, controlling for cigarette smoking and other covariates. For asthma (n=15 studies), the pooled adjusted odds ratio (aOR) was 1.39 (95% CI 1.28–1.51); for COPD (n=9 studies) the aOR was 1.49 (95% CI 1.36–1.65). Laboratory studies consistently show an effect of e-cigarettes on biological processes related to respiratory harm and susceptibility to illness, with e-cigarette conditions differing significantly from clean-air controls, although sometimes less than for cigarettes.

Conclusions

The evidence from epidemiological studies meets established criteria for consistency, strength of effect, temporality, and in some cases a dose–response gradient. Biological plausibility is indicated by evidence from multiple laboratory studies. We conclude that e-cigarette use has consequences for asthma and COPD, which is of concern for respirology and public health.

Epidemiological studies show a relationship of e-cigarette use with asthma and COPD, and laboratory studies show their adverse effects on four biological processes. It can be concluded that e-cigarette use is of significant concern for public health.https://bit.ly/3drH4pj

Pilot Study of Electronic Nicotine Delivery Systems (ENDS) Cessation Methods

Currently, 7.6% of the U.S. young adults aged 18-24 years old use e-cigarettes. This study piloted three methods of Electronic Nicotine Delivery Systems (ENDS) cessation by measuring cessation rates, motivational techniques that contributed to cessation success, and participants' changes after decreasing vape use. Participants were randomized into three study arms (nicotine replacement therapy (NRT) + behavioral support, vape-taper + behavioral support, self-guided) in a 1:1:1 ratio. All participants were invited to attend nine in-person or phone appointments over the 6-month study period. At 12 weeks, 3 of 7 (42.9%) participants in the NRT + behavioral support arm, 6 of 8 (75%) vape-taper + behavioral support arm, and 7 of 9 (77.8%) self-guided arm self-reported being vape-free and nicotine-free. At 6 months, 3 of 7 (42.9%) participants in the NRT + behavioral support arm, 6 of 8 (75%) vape-taper + behavioral support arm, and 4 of 9 (44.4%) self-guided arm self-reported being vape-free and nicotine-free. A challenge to quitting and remain quit is social pressures, but participants identified self-control and establishing new habits to be the best methods to overcome the desire to vape. Participants who received behavioral support and a vape-taper plan from pharmacists were more likely to be vape-free and nicotine-free at 6 months.

Predictors of electronic cigarette use among Swedish teenagers: a population-based cohort study

OBJECTIVES

The aim was to identify predictors of electronic cigarette (e-cigarette) use among teenagers.

DESIGN AND SETTING

A prospective population-based cohort study of schoolchildren in northern Sweden.

PARTICIPANTS

In 2006, a cohort study about asthma and allergic diseases among schoolchildren started within the Obstructive Lung Disease in Northern Sweden studies. The study sample (n=2185) was recruited at age 7-8 years, and participated in questionnaire surveys at age 14-15 and 19 years. The questionnaire included questions about respiratory symptoms, living conditions, upper secondary education, physical activity, diet, health-related quality of life, parental smoking and parental occupation. Questions about tobacco use were included at age 14-15 and 19 years.

PRIMARY OUTCOME

E-cigarette use at age 19 years.

RESULTS

At age 19 years, 21.4% had ever tried e-cigarettes and 4.2% were current users. Among those who were daily tobacco smokers at age 14-15 years, 60.9% had tried e-cigarettes at age 19 years compared with 19.1% of never-smokers and 34.0% of occasional smokers (p<0.001). Among those who had tried e-cigarettes, 28.1% were never smokers both at age 14-15 and 19 years, and 14.4% were never smokers among the current e-cigarette users. In unadjusted analyses, e-cigarette use was associated with daily smoking, use of snus and having a smoking father at age 14-15 years, as well as with attending vocational education, physical inactivity and unhealthy diet. In adjusted analyses, current e-cigarette use was associated with daily tobacco smoking at age 14-15 years (OR 6.27; 95% CI 3.12 to 12.58), attending a vocational art programme (OR 2.22; 95% CI 1.04 to 4.77) and inversely associated with eating a healthy diet (OR 0.74; 95% CI 0.59 to 0.92).

CONCLUSIONS

E-cigarette use was associated with personal and parental tobacco use, as well as with physical inactivity, unhealthy diet and attending vocational upper secondary education. Importantly, almost one-third of those who had tried e-cigarettes at age 19 years had never been tobacco smokers.

Exclusive E-Cigarette Users Report Lower Levels of Respiratory Symptoms Relative to Dual E-Cigarette and Cigarette Users

INTRODUCTION

Exclusive e-cigarette use has been shown to be associated with reduced levels of respiratory symptoms relative to smoking combustible cigarettes; this association has been less frequently studied in smokers using advanced-generation e-cigarette devices. Advanced-generation devices generate denser vapor than either early generation or pod-style devices, and engender longer inhalations; these vaping topography patterns may contribute to respiratory symptoms.

METHODS

In a single-session, cross-sectional study of exclusive e-cigarette users (N = 59) and dual users of e-cigarettes and cigarettes (N = 54), participants completed questionnaires, including the American Thoracic Society Questionnaire (ATSQ) and were videotaped vaping their own device in the lab for 1 hour. Using a hierarchical regression method, we examined whether topography variables, level of nicotine concentration used in their e-cigarette device in the past month, e-cigarette dependence, amount of e-cigarette use in the past month, and smoking status (any smoking in the last month vs. none) predicted ATSQ score severity.

RESULTS

There was a significant mean difference in ATSQ score across smoking status, with greater ATSQ scores for vapers who also smoked cigarettes (19.0, SD = 6.7) than for exclusive vapers (13.4, SD = 5.3). In the final model, of the predictors of interest, only cigarette smoking status predicted significantly greater ATSQ scores (overall F = 2.51, p = .006; R2 = .26; smoking status β = 0.39, p < .0001).

CONCLUSIONS

Findings suggest that differences in respiratory symptoms between dual and exclusive e-cigarette users appear to be attributable to combustible cigarette smoking, rather than more intense or frequent e-cigarette use across groups.

IMPLICATIONS

In this comparison of exclusive advanced-generation vape device users (N = 59) versus dual users of these devices and combustible cigarettes (N = 54), we set out to determine the extent to which smoking status and e-cigarette use variables predicted self-reported respiratory symptom severity. We found that dual users showed greater respiratory symptom severity (ATSQ scores) than exclusive vapers. Despite examining vaping topography and other variables, smoking status and race were the only significant predictor of respiratory symptoms. We conclude that combustible cigarette use, not individual vaping topography, likely accounts for differences in respiratory symptoms between dual users and exclusive vapers.

User-Perceived Negative Respiratory Symptoms Associated with Electronic Cigarette Use

INTRODUCTION

Electronic cigarettes (ECIGs) expose users to an aerosol containing chemicals, which could affect the respiratory system negatively. This study examined negative respiratory symptoms associated with ECIG use.

METHODS

In 2019, adult current ECIG users from 24 US states who reported experiencing negative respiratory symptoms from ECIG use (n = 49; 44.9% women; mean age = 35.2, SD = 11.5) completed an online survey and brainstormed statements that completed the prompt: "A specific negative effect or symptom related to my breathing, nose, mouth, throat, or lungs that I have experienced from vaping/using my e-cigarette is..." Participants sorted the final list of 56 statements into groups of similar content and rated statements on how true they were for them. Multidimensional scaling analysis identified thematic clusters.

RESULTS

Eight ECIG use respiratory symptom clusters identified in analysis included Mucus and Congestion, Fatigue, Throat Symptoms, Breathing Problems, Mouth Symptoms, Chest Symptoms, Illness Symptoms, and Nose and Sinus Symptoms. Highly rated (ie, most common) symptoms included dry throat or mouth, fatigue during physical activity, coughing, shortness of breath, excessive phlegm, and bad taste in mouth. Mean cluster ratings did not differ based on lifetime cigarette smoking status (100 lifetime cigarettes smoked), but current cigarette smokers (ie, dual users) rated the Fatigue, Breathing Problems, Mucus and Congestion, and Nose and Sinus Symptoms clusters higher than noncurrent cigarette smokers.

CONCLUSIONS

Participant-identified respiratory symptoms perceived to be ECIG related, many similar to cigarette smoking symptoms. Future research should assess if these symptoms are associated with other negative health outcomes.

IMPLICATIONS

ECIG use exposes users to chemicals that may have negative health impacts on the respiratory system. Limited research has examined the broad range of negative respiratory symptoms associated with e-cigarette use. This study identified that ECIG-cigarette users perceive their ECIG use to be associated with negative respiratory symptoms. Many e-cigarette user-reported negative respiratory symptoms are similar to those associated with cigarette smoking, though some appear unique to e-cigarette use. Future research should continue to monitor respiratory symptoms reported by ECIG users and whether these are associated with health outcomes over time.

Mental Health and the Association between Asthma and E-cigarette Use among Young Adults in The United States: A Mediation Analysis

Background: Asthma is associated with a greater likelihood of e-cigarette use among young adults, which may increase the risk of pulmonary complications. Because substance use trajectories emerge in early adulthood, it is important to identify factors that may be important in addressing this new public health threat. One such factor may be poor mental health. Methods: Data were extracted from the 2018 Behavioral Risk Factor Surveillance System (BRFSS). Current and former asthma status was measured by self-reported lifetime and current asthma status; mental health functioning was measured by the number of self-reported bad mental health days during the past 30 days; e-cigarette use was measured by self-reported current e-cigarette use. We tested the hypothesis that mental health mediates the association between asthma status and e-cigarette use among young adults using structural equation modeling. Results: The prevalence of e-cigarette use was significantly higher among young adults with current (9.90%) or former asthma (13.09%) than those without asthma (9.58%). Furthermore, the number of bad mental health days in the past 30 days was significantly greater among young adults with current or former asthma than among those without asthma (Mean (Standard Deviation): 6.85 (0.42), 4.18 (0.85) versus 3.83 (0.17)), respectively. Finally, we found a statistically significant indirect effect of asthma on the likelihood of e-cigarette use through mental health such that the higher prevalence of e-cigarette use among those with current or former asthma was statistically accounted for by a greater number of bad mental health days in the past 30 days. Conclusions: Consistent with mediation, poorer mental health accounted for the higher prevalence of e-cigarette use among those with asthma. However, longitudinal studies are needed to interrogate causal relationships, including the effects of e-cigarette use on mental health. Mental health services may play an important role in improving health and wellbeing in this vulnerable population.

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

Background

Electronic cigarettes (e-cigarettes) are widely promoted as harm-reduction products for smokers, and smokers commonly perceive them as less harmful than combustible cigarettes. One of the key questions regarding public health consequences of e-cigarettes is the magnitude of harm reduction achievable by smokers who switch from combustible cigarettes to e-cigarettes. We conducted a systematic literature review of epidemiological studies that estimated odds of respiratory and cardiovascular outcomes among former smokers who use e-cigarettes compared to current smokers.

Methods

This systematic review was conducted in accordance with the Preferred Reporting Items for Systematic Review and Meta-Analysis (PRISMA) statement. We searched the PubMed and Embase databases in September 2020 to identify epidemiological studies that compared odds of cardiovascular and respiratory outcomes among former smokers who transitioned to e-cigarettes relative to odds among current smokers not using e-cigarettes (current exclusive smokers). We included studies that provided direct estimates of relevant odds ratios (ORs). We also included studies where indirect estimates of relevant ORs could be calculated based on published results. Two reviewers independently extracted data and conducted quality appraisals.

Results

Six population-based studies with sample sizes ranging from 19,475 to 161,529 respondents met review inclusion criteria, five of which were cross-sectional and one longitudinal. Three studies reported respiratory outcomes and three reported cardiovascular outcomes. ORs of respiratory outcomes (including chronic obstructive pulmonary disease, chronic bronchitis, emphysema, asthma, and wheezing) in former smokers who transitioned to e-cigarettes versus current exclusive smokers were below 1.0, ranging from 0.58 (95%CI 0.36–0.94) to 0.66 (95%CI 0.50–0.87; all p < 0.05). All ORs for cardiovascular outcomes (including stroke, myocardial infarction, and coronary heart disease) did not differ significantly from 1.0.

Conclusion

Though our review included a small number of studies, it provided consistent results. Former smokers who transitioned to e-cigarettes showed ~ 40% lower odds of respiratory outcomes compared to current exclusive smokers. Switching from smoking to e-cigarette does not appear to significantly lower odds of cardiovascular outcomes. Since the utility of cross-sectional studies for causal inference remains limited, both randomized controlled trials and prospective cohort studies are needed to better evaluate contributions of e-cigarettes as harm reduction tools for smokers.