A scoping review of studies on the health impact of electronic nicotine delivery systems

Electronic cigarette use, related health outcomes and policy interventions in the USA: a call for research to fill evidence gaps

The population-level health consequences of electronic cigarette (e-cigarette) use are heavily debated. This special communication provides updated evidence and identifies knowledge gaps across domains including: (1) health-related outcomes associated with e-cigarette use; (2) initiation and use of e-cigarettes among youth and young adults; (3) concurrent use of electronic and combustible cigarettes; (4) transitions from combustible cigarette use to exclusive e-cigarette use among adults who currently smoke cigarettes and (5) existing e-cigarette-related policy interventions. Literature was searched through PubMed and Medline for systematic reviews, scoping reviews, meta-analyses and primary research articles including emerging topics not covered in reviews published between 1 January 2017 and 1 January 2024. E-cigarette use is associated with several adverse acute health outcomes; there is currently insufficient longitudinal evidence to predict chronic health outcomes. Prevalence of e-cigarette use among youth is considerable and may be associated with subsequent combustible cigarette smoking. Evidence for the health and behavioural impact of dual use of e-cigarettes and combustible cigarettes is limited by imprecise measurement of exposure. Evidence on adults completely substituting combustible cigarettes for e-cigarettes is strong in clinical trials; observational studies do not show complete substitution. Finally, the effects of e-cigarette-related policy interventions to restrict e-cigarette consumption are currently limited in scope and too short-lived to draw causal inferences. Substantial evidence gaps related to the use, associated health impacts and regulation of e-cigarettes in the USA are identified, and we suggest key areas for future research to address that are crucial for informing the public health approach to e-cigarettes.

Nicotine and Toxicant Exposure among Individuals using both Combustible Cigarettes and E-cigarettes Based on Level of Product Use

INTRODUCTION

Dual use of combustible cigarettes and e-cigarettes is the most common multiple tobacco-use behavior in the United States, but its long-term health impact remains unclear. Biomarkers of exposure (BOE) can help identify potential health risks of dual use.

METHODS

We analyzed data from 2,679 adult participants from Wave 5 of the Population Assessment on Tobacco and Health Study, a U.S. nationally representative study, including individuals reporting current exclusive cigarette use (n = 1,913), exclusive e-cigarette use (n = 316), and dual use (n = 450). Eight subgroups were created based on self-reported high/low (above/below mean) cigarettes per day (CPD) and days of e-cigarette use in past the 30 days (ECIG). Adjusted geometric mean concentrations were compared for total nicotine equivalents, 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL), three volatile organic compounds (VOCs), and heavy metals (lead and cadmium).

RESULTS

Individuals reporting dual use did not differ from those reporting exclusive cigarette use on CPD (13.1 vs. 11.8, respectively). Dual-use groups with high CPD had higher levels of NNAL and VOCs compared to those with low CPD (eg, NNAL for high CPD/high ECIG: 257.07 ng/mg creatinine vs. low CPD/high ECIG: 64.57 ng/mg creatinine, p < .001; high CPD/low ECIG: 312.02 ng/mg creatinine vs. low CPD/low ECIG: 144.11 ng/mg creatinine, p < .001). Cigarette use (dual or exclusive use) was generally associated with higher BOE than exclusive e-cigarette use, though metal exposure did not differ between groups.

CONCLUSIONS

Dual use and exclusive cigarette use are associated with higher toxicant exposure compared to exclusive e-cigarette use.

IMPLICATIONS

In this population-based cross-sectional study, individuals reporting dual use appear to have nicotine and toxicant exposure at least at the same level as those using cigarettes alone and higher than exclusive e-cigarette use (except for metals). Given the adverse health consequences of dual use, including potential cancer risk, our findings highlight the need for clinicians and public health practitioners to increase awareness of the potential risks associated with dual use.

Respiratory symptoms among e-cigarette users without an established smoking history in the VERITAS cohort

Prior research on e-cigarettes' health impacts is inconclusive due to confounding by previous tobacco smoking. Studies of e-cigarette use among people without an established smoking history are informative for this question. A cross-sectional survey was administered across six geopolitical world regions to adults aged 18+ without a history of established cigarette smoking or regular use of other nicotine/tobacco products. Two cohorts were defined based on e-cigarette use: "Vapers Cohort" (N = 491) who used e-cigarettes in the past 7 days and "Control Cohort" (N = 247) who never regularly used e-cigarettes. Frequency of respiratory symptoms (Respiratory Symptom Evaluation Score (RSES)) were compared between cohorts, adjusting for sociodemographics. Tobacco use history and patterns of e-cigarette use was also examined. Respiratory symptoms were rare among both the Vapers and Control Cohorts: 83.3% and 88.4%, respectively, reported "rarely" or "never" experiencing all five RSES items (p = 0.125). The Vapers (vs. Control) Cohort reported modestly more frequent respiratory symptoms (adjusted mean RSES 1.61 vs. 1.43, respectively, p < 0.001); however, this difference (0.18) did not reach the threshold of clinical relevance (0.57). The Vapers (vs. Control) Cohort more often reported former cigarette experimentation (30.8% vs. 12.1%) and former infrequent use of other nicotine/tobacco products (18.1% vs. 5.8%). The Vapers Cohort most often used disposable devices (63.7%) and multiple flavors (approximately 70-80% across primary device type). In this cohort of adults without a history of established combustible tobacco use, e-cigarette use was statistically linked to more frequent respiratory symptoms, though not in a clinically meaningful way. The cross-sectional design of this study cannot establish causality between e-cigarette use and respiratory symptoms.

Association of electronic cigarette use and suicidal behaviors: a systematic review and meta-analysis

BACKGROUND

The proliferation of electronic cigarettes (e-cigarettes) has presented new challenges in public health, particularly among adolescents and young adults. While marketed as safer than tobacco and as cessation aids, e-cigarettes have raised concerns about their long-term health and psychosocial impacts, including potential links to increased suicidal behaviors. This study aims to evaluate the relationship between e-cigarette use and suicidal behaviors by conducting a systematic review of the current literature.

METHODS

We searched PubMed, Web of Science, and EMBASE for studies up to March 10, 2024, examining the relationship between e-cigarette use and suicidal behaviors. Eligible studies included cross-sectional, longitudinal, retrospective, prospective, and case-control designs. Meta-analysis was performed to calculate pooled odds ratios (ORs). Newcastle Ottawa scale was used to assess the quality of studies. R software (V 4.3) was used to perform the meta-analysis.

RESULTS

Our analysis included fourteen studies, predominantly from the US and Korea, with participants ranging from 1,151 to 255,887. The meta-analysis identified a significant association between e-cigarette use and an increased risk of suicidal ideation (OR = 1.489, 95% CI: 1.357 to 1.621), suicide attempts (OR = 2.497, 95% CI: 1.999 to 3.996), and suicidal planning (OR = 2.310, 95% CI: 1.810 to 2.810). Heterogeneity was noted among the studies.

CONCLUSION

E-cigarette use is significantly associated with the risk of suicidal behaviors, particularly among adolescents. The findings underscore the necessity for caution in endorsing e-cigarettes as a safer smoking alternative and call for more extensive research to understand the underlying mechanisms. Public health strategies should be developed to address and mitigate the risks of suicidal behaviors among e-cigarette users.

A Global Health Survey of People Who Vape but Never Smoked: Protocol for the VERITAS (Vaping Effects: Real-World International Surveillance) Study

BACKGROUND

There is only limited information about the health effects of regular vaping. Research on the health status of people who used to smoke faces the challenge that previous smoking may have caused unknown health effects. Only studies of people who vape but have never smoked combustible cigarettes can enable the detection of harms attributable to vaping. Large prospective studies of well-characterized electronic cigarette users with and without a history of combustible cigarette smoking are warranted to establish the long-term effects of regular vaping on respiratory health.

OBJECTIVE

We will conduct a global cross-sectional survey of individuals from 6 world regions. Respiratory symptoms will be assessed using a validated questionnaire-the Respiratory Symptom Experience Scale (RSES). Current vapers who are nonusers of other tobacco or nicotine products will be compared with matched controls who are nonusers of vapes and other tobacco or nicotine products.

METHODS

This will be a multicountry, cross-sectional internet-based survey of 750 adults aged ≥18 years who satisfy the criteria for inclusion in either a cohort of people who exclusively vape and who are nonusers of other tobacco or nicotine products ("vapers cohort"; target N=500) or a cohort of nonvapers who are also nonusers of other tobacco or nicotine products ("controls cohort"; target N=250). The primary end point of the study is the RSES score. RSES scores of people in the "vapers cohort" will be compared with those of people in the "controls cohort." Additionally, the study will collect data to characterize patterns of vaping product use among the vapers cohort. Data collection will include information about the age initiation of using vape products, reasons for starting and continuing the use of vape products, specific types of products used, flavors and nicotine strengths of recently used products, as well as the frequency and intensity of product use in the past 30 days.

RESULTS

Participant recruitment started in April 2023, and enrollment was completed by November 2023 with 748 participants. Results will be reported in 2024.

CONCLUSIONS

This will be the first study providing key insights into respiratory health effects associated with using electronic cigarettes in people who vape with no established use of combustible cigarettes or other tobacco or nicotine products.

INTERNATIONAL REGISTERED REPORT IDENTIFIER (IRRID)

DERR1-10.2196/54236.

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.

Electronic Nicotine Delivery Systems (ENDS) use Among Members of a Community Engagement Program

Electronic nicotine delivery systems (ENDS) are relatively new and ENDS use data from community engagement programs may help us understand usage patterns and facilitate targeted longitudinal studies. Community members in Florida, USA, were asked about ENDS use, tobacco use, and health history/concerns by Community Health Workers. Among 7253 members recruited during 2014 to 2021 into our HealthStreet program, 1177 had ever used ENDS; the proportion increased from 12 to 27% from 2014 to 2021 (adjusted odds ratio (aOR) 2.5; 95% CI 1.7-3.5; Ever versus never used ENDS). Ever tobacco use was strongly associated with ENDS use; 69% of ever users were current tobacco users. Demographic determinants (sex, age, race) and food insecurity were strongest predictors of ENDS use. Most who had ever used ENDS were aged 18-25 (aOR 5.9; 95% CI 4.6-7.6; vs. aged 60 + years), White (aOR 3.7; 95% CI 3.2-4.3; vs. Black/African American), male (aOR 1.5; 95% CI 1.3-1.7; vs. female), and recently food insecure (aOR 1.8; 95% CI 1.5-2.0; vs. not recently food insecure). Those with respiratory issues were more likely to have used ENDS compared to those without (aOR 2.0; 95% CI 1.6-2.6; aOR 1.3; 95% CI 1.1-1.5). Members concerned about hypertension were less likely to have used ENDS (aOR 0.7; 95% CI 0.5-0.9). In this relatively rural, micropolitan sample, tobacco use, socio-economic determinants, and certain health history/concerns were strongly associated with ENDS use. Community outreach approaches are needed to further understand these factors and implement interventions.

Perceived Health and Capacity to Cope With Stress in Recent Ex-smokers: Impact of Vaping Versus Quitting All Nicotine

INTRODUCTION

Little is known about the continued use of nicotine following smoking cessation on perceived well-being in comparison to complete cessation of nicotine use.

AIMS AND METHODS

To explore aspects of perceived well-being and coping among recent ex-smokers as a function of vaping status. Ever-daily smokers in the International Tobacco Control 4 country smoking and vaping surveys in 2016 (w1 N = 883) and 2018 (w2 N = 1088). Cross-sectional associations and longitudinal samples for those who quit between waves and those who quit at w1 and maintained abstinence to w2. Main outcome measures were: Past 30 days of depression symptoms, perceived stress, stress management since quitting, and change in perceived day-to-day health.

RESULTS

In the cross-sectional analyses vapers were more likely to report both improved stress management (aOR = 1.71, 95% CI 1.23-2.36) and perceived day-to-day health (aOR = 1.65, 95% CI 1.26-2.16) than nicotine abstainers. In the longitudinal analyses, smokers who switched to vaping between waves (n = 372) were more likely to report depression symptoms at w2 (aOR = 2.00, 95% CI 1.09-3.65) but reported improved perceived health (aOR = 1.92, 95% CI 1.16-3.20). For the past daily smokers who remained quit between waves (n = 382), vapers were more likely to report improved stress management relative to abstainers (RRR = 5.05. 95% CI 1.19-21.40). There were no other significant differences between vapers and nicotine abstainers.

CONCLUSIONS

There is little evidence to support the view that perceptions of well-being deteriorate in vapers compared to complete nicotine abstainers in the immediate years after smoking cessation.

IMPLICATIONS

This study could find no conclusive evidence that the continued use of nicotine via e-cigarettes was detrimental to health compared to completely stopping nicotine intake altogether. Our results would suggest that continuing to use nicotine may even result in some benefits in the short term such as improved stress management, however further longitudinal studies are required to examine if these effects are restricted to the early post-quitting phase and whether other positive or negative effects on psychosocial health emerge in the future.

A Close Look at Vaping in Adolescents and Young Adults in the United States

Vaping by adolescents and young adults is a legitimate concern as there is a risk that some may start smoking and that electronic cigarette (EC) use may have adverse effects in the developing lungs of adolescents. This commentary provides updated information on vaping patterns among adolescents and young adults in the United States, as well as the impact of EC usage on respiratory health. EC use has surged greatly among high school students and young adults over the last decade but fortunately has declined significantly since its peak in 2019. During the same time period, smoking rates have constantly fallen to new low record levels. These trends argue against EC use as a gateway to smoking. Most EC usage is infrequent and unlikely to increase a person's risk of negative health consequences. Furthermore, the majority of EC usage has happened among those who have previously smoked. There is a dearth of data on the long-term health implications of EC usage in adolescents and young adults. We do not know whether short-term or intermittent use of EC in youth can lead to negative health outcomes in adulthood, and long-term high-quality studies in well-defined groups are needed. Although vaping has been linked to respiratory symptoms, they tend to be transient and of uncertain significance. This commentary provides up-to-date information so health care providers can give objective and responsible medical advice on EC usage.

Health impact of e-cigarettes and heated tobacco products in chronic obstructive pulmonary disease: current and emerging evidence

INTRODUCTION

Quitting is the only proven method to attenuate the progression of chronic obstructive pulmonary disease (COPD). However, most COPD smokers do not seem to respond to smoking cessation interventions and may benefit by lessening the negative health effects of long-term cigarette smoke exposure by switching to non-combustible nicotine delivery alternatives, such as heated tobacco products (HTPs) and e-cigarettes (ECs).

AREAS COVERED

Compared with conventional cigarettes, HTPs and ECs offer substantial reduction in exposure to toxic chemicals and have the potential to reduce harm from cigarette smoke when used as tobacco cigarette substitutes. In this review, we examine the available clinical studies and population surveys on the respiratory health effects of ECs and HTPs in COPD patients.

EXPERT OPINION

The current research on the impact of ECs and HTPs on COPD patients' health is limited, and more high-quality studies are needed to draw definitive conclusions. However, this review provides a comprehensive overview of the available literature for health professionals looking to advise COPD patients on the use of these products. While ECs and HTPs may offer some benefits in reducing harm from cigarette smoke, their long-term effects on COPD patients' health are still unclear.

On the toxicity of e-cigarettes consumption: Focus on pathological cellular mechanisms

Tobacco smoking remains without a doubt one of the leading causes of premature death worldwide. In combination with conventional protocols for smoking cessation, e-cigarettes have been proposed as a useful tool to quit smoking. Advertised as almost free of toxic effects, e-cigarettes have rapidly increased their popularity, becoming a sought-after device, especially among young people. Recently some health concerns about e-cigarette consumption are being raised. It is well known that they can release several toxic compounds, some of which are carcinogenic to humans, and emerging results are now outlining the risks related to the onset of respiratory and cardiovascular diseases and even cancer. The present review shows the emerging evidence about the role of technical components of the devices, the e-liquid composition as well as customization by consumers. The primary topics we discuss are the main toxicological aspects associated with e-cigarette consumption, focusing on the molecular pathways involved. Here it will be shown how exposure to e-cigarette aerosol induces stress/mitochondrial toxicity, DNA breaks/fragmentation following the same pathological pathways triggered by tobacco smoke, including the deregulation of molecular signalling axis associated with cancer progression and cell migration. Risk to fertility and pregnancy, as well as cardiovascular risk associated with e-cigarette use, have also been reported.

Tests for confounding with cigarette smoking in the association of E-cigarette use with respiratory disorder: 2020 National-Sample Data

Associations of e-cigarette use with respiratory disorder have been demonstrated but it has been unclear whether these are confounded by current or previous cigarette smoking. We address this question through studying different time frames for e-cigarette use and respiratory disorders in 2020 BRFSS data (N = 214,945). E-cigarette use and combustible cigarette smoking were classified into four categories: Participant never used either (Nonuse); used e-cigarettes/cigarettes but not in the past 30 days (Former Use), used in past 30 days on some days (Nondaily Use), or used past 30 days on all days (Daily Use). Contrasts for e-cigarette status and cigarette status (with nonuse as reference group) were entered with covariates in logistic regression with asthma or COPD as criterion. Stratified analyses of e-cigarette use were also performed for smokers and nonsmokers. In the total sample, results showed independent positive associations with both lifetime and current asthma for Former, Nondaily, and Daily e-cigarette use (mostly p < .0001) and the three cigarette indices. Significant positive associations with COPD were found for the three e-cigarette indices (p < .0001) and all the cigarette indices. Stratified analyses showed significant associations of e-cigarette use with respiratory disorder among nonsmokers as well as among smokers. We conclude that independent associations for former e-cigarette use (controlling for current/former smoking) and significant associations of e-cigarette use with respiratory disorder among nonsmokers indicate these associations are not confounded with cigarette smoking and suggest reverse causation is implausible. Findings for former use are discussed with reference to possible mechanisms including sensitization effects.

Association between Daily Pattern of Physical Activity and Depression: A Systematic Review

Recent research suggested that daily pattern of physical activity (PA) may have an important association with depression, but findings are limited and contradictory. Our aim was to conduct a systematic review of the literature to summarize the literature evidence on the association between timing of PA and depression. A comprehensive search of PubMed/Medline and Scopus databases has been performed, and a total of five manuscripts have been thoroughly reviewed. The performed descriptive analysis shows lower levels of PA among individuals with depression or depressive symptoms, although evidence on the 24 h pattern of PA and depression is limited. An interesting finding is the association between lower PA during the morning, higher PA late in the evening (night), and depression or depressive symptoms. However, definitive conclusions could not be drawn due to the observational nature of the studies, their limited number, the high heterogeneity in the sample populations, and the studies’ differing outcome definitions and exposure assessments. Future studies considering not only the level of PA but also its daily variability might be important to further explore this novel area of research.

Cigarette Smoking and Asthma

Globally, around half the adult asthma population are current or former cigarette smokers. Cigarette smoking and asthma interact to induce an "asthma-smoking phenotype(s)," which has important implications for diagnosis, pathogenic mechanisms, and management. The lack of progress in understanding the effects of smoking on adults with asthma is due in part to their exclusion from most investigative studies and large clinical trials. In this review, we summarize the adverse clinical outcomes associated with cigarette smoking in asthma, highlight challenges in diagnosing asthma among cigarette smokers with chronic respiratory symptoms, particularly in older individuals with a long-standing smoking history, and review pathogenic mechanisms involving smoking- and asthma-related airway inflammation, tissue remodeling, corticosteroid insensitivity, and low-grade systemic inflammation. We discuss the key components of management including the importance of smoking cessation strategies, evidence for the effectiveness of the Global Initiative for Asthma recommendations on treatment in cigarette smokers, and the role of treatable traits such as type 2 eosinophilic airway inflammation. Lastly, we provide an algorithm to aid clinicians to manage current and former smokers with asthma. In the future, controlled and pragmatic trials in real-world populations should include cigarette smokers with asthma to provide an evidence base for treatment recommendations.

Analysis of common methodological flaws in the highest cited e-cigarette epidemiology research

The prevalence of vaping, also known as using e-cigarettes, vapes and vape pens, has prompted a demand for reliable, evidence-based research. However, published literature on the topic of vaping often raises concerns, characterized by serious flaws and a failure to adhere to accepted scientific methodologies. In this narrative review, we analyze popular vaping studies published in medical journals that purport to evaluate the association of vaping and smoking cessation, smoking initiation or health outcomes. We analyzed 24 included studies to identify the questions they claimed to address, stated methods, manner of implementation, discussions, and stated conclusions. After critical appraisal, we noted a multiplicity of flaws in these studies, and identified patterns as to the nature of such flaws. Many studies lacked a clear hypothesis statement: to the extent that a hypothesis could be inferred, the methods were not tailored to address the question of interest. Moreover, main outcome measures were poorly identified, and data analysis was further complicated by failure to control for confounding factors. The body of literature on "gateway" theory for the initiation of smoking was particularly unreliable. Overall, the results and discussion contained numerous unreliable assertions due to poor methods, including data collection that lacked relevance, and assertions that were unfounded. Many researchers claimed to find a causal association while not supporting such findings with meaningful data: the discussions and conclusions of such studies were, therefore, misleading. Herein, we identify the common flaws in the study design, methodology, and implementation found in published vaping studies. We present our summary recommendations for future vaping research. Our aim is to prompt future researchers to adhere to scientific methods to produce more reliable findings and conclusions in the field of vaping research.