Nicotine absorption during electronic cigarette use among regular users

Cigarette Smoking Relapse Among People Who Switched to E-cigarettes or Other Tobacco Products

INTRODUCTION

Little is known about how quitting and switching to other tobacco products affects cigarette smoking relapse. Additionally, there is no consensus on the best definition of relapse.

AIMS AND METHODS

Respondents who smoked cigarettes at baseline, had quit by the first follow-up, and completed the second follow-up survey in the Population Assessment of Tobacco and Health Study were included. We employed multivariable logistic regressions to assess the association between non-cigarette tobacco use at follow-up 1 and smoking relapse risk at follow-up 2, considering three definitions of relapse.

RESULTS

54.8% of the 1686 respondents who had recently quit smoking cigarettes relapsed according to Measure I (any smoking in the past 12 months), 40.3% using Measure II (any smoking in the past 30 days), and 30.1% using Measure III (smoked on ≥3 days in the past 30 days). Compared with no tobacco use at follow-up 1, any tobacco use was associated with increased relapse risk using Measure I (adjusted risk difference [aRD] = 7.14, CI [0.64 to 13.64]). The association was nonsignificant using Measures II (aRD = -0.53, CI [-6.62 to 5.56]) or III (aRD = -4.11, CI [-9.28 to 1.06]). Similarly, exclusive e-cigarette use was significantly associated with Measure I, but not with Measures II or III.

CONCLUSIONS

Compared with respondents who had recently quit and were tobacco-free at follow-up 1, those who switched to non-cigarette tobacco products may be more likely to slip but showed no difference in the likelihood of relapse when employing a relapse definition less strict than any smoking in the past 12 months.

IMPLICATIONS

The distinction between a slip and relapse needs to be considered more carefully, with researchers undertaking further studies that help us contemplate how we should define relapse. People who recently quit smoking cigarettes and switched to non-cigarette tobacco products (including e-cigarettes) may be more likely to slip compared to people who recently quit and were tobacco-free, but they are not clearly more likely to relapse.

Does the time to nicotine dependence vary by internalizing symptoms for young people who use e-cigarettes? An analysis of the Population Assessment of Tobacco and Health (PATH) study, (Waves 1-5; 2013-2019)

OBJECTIVE

To determine the relationship between past-year internalizing symptoms and the time to first report of signs of nicotine dependence among young people.

METHODS

Secondary analysis using data from the Population Assessment of Tobacco and Health (PATH) (Waves 1-5; 2013-2019). The study included 2,102 (N = 5,031,691) young people (age 12-23 years) who reported past-30-day (P30D) e-cigarette use in one or more waves. Kaplan Meier curves, stratified by past year internalizing symptoms were used to estimate the time to the first report of three nicotine dependence symptoms (i.e., use within 30 min of waking, cravings, and really needing to use) following the first P30D e-cigarette use. Cox proportional hazard models were used to estimate crude and adjusted hazard ratios (AHR), comparing any past year internalizing symptoms to no past year internalizing symptoms.

RESULTS

We found no significant differences between past year internalizing symptoms and the time to the first report of cravings (AHR = 1.30, 95 % CI = 92-1.85), really needing to use (AHR = 1.31; 95 % CI = 0.92-1.89) and use within 30 min of waking for follow-up times 0-156 weeks (AHR = 0.84; 95 % CI = 0.55-1.30) and > 156 weeks (AHR = 0.41; 95 % CI = 0.04-4.67) respectively.

CONCLUSION

Past year internalizing symptoms did not modify the time to the first report of nicotine dependence among youth with P30D e-cigarette use. Further research is needed to understand how changing internalizing symptoms and e-cigarette use frequency influence nicotine dependence over time and, how this relationship impacts cessation behavior.

Concurrent E-cigarette Use While Enrolled in a Smoking Cessation Program: Associations Between Frequency of Use, Motives for Use, and Smoking Cessation

INTRODUCTION

Trial evidence suggests that e-cigarettes may aid in quitting smoking, while observational studies have found conflicting results. However, many observational studies have not adjusted for important differences between e-cigarette users and non-users.

AIMS AND METHODS

We aimed to determine the association between e-cigarette use frequency and motivation to use e-cigarettes to quit smoking, and smoking cessation using data from Canada's largest smoking cessation program. Participants who completed a baseline assessment and 6-month follow-up questionnaire were divided post hoc into four groups based on their self-reported e-cigarette use during the 30 days before baseline: (1) non-users; (2) users of e-cigarettes not containing nicotine; (3) occasional users; and (4) frequent users. Occasional and frequent users were further divided into two groups based on whether they reported using e-cigarettes to quit smoking. Abstinence at 6-month follow-up (7-day point prevalence abstinence) was compared among groups.

RESULTS

Adjusted quit probabilities were significantly higher (both p < .001) for frequent baseline e-cigarette users (31.6%; 95% CI = 29.3%, 33.8%) than for non-users (25.8%; 25.3% and 26.3%) or occasional users (24.2%; 22.5% and 26.0%). Unadjusted proportions favored non-users over occasional users (p < .001), but this was not significant after adjustment (p = .06). People using e-cigarettes to quit smoking were not likelier than other users to be successful, but were likelier to report frequent e-cigarette use during follow-up.

CONCLUSIONS

Frequent baseline e-cigarette use predicted successful smoking cessation, compared to occasional and non-users. Use of e-cigarettes to quit did not predict smoking cessation but was associated with continued use during follow-up, perhaps due in part to planned transitions to e-cigarettes.

IMPLICATIONS

Prior observational studies investigating e-cigarette use for smoking cessation have found that occasional users have poorer outcomes than either frequent or non-users. Consistent with these studies, occasional users in our data also had poorer outcomes. However, after adjustment for variables associated with cessation success, we found that cessation probabilities did not differ between occasional and non-users. These findings are consistent with trial data showing the benefit of e-cigarette use among people trying to quit smoking. Results of this study suggest that differences between trials and previous observational studies may be because of unaddressed confounding in the latter.

Time to first report of signs of nicotine dependence among youth who use e-cigarettes and cigarettes in the United States: A nationally representative cohort study, findings from the Population Assessment of Tobacco and Health, 2013-2019

OBJECTIVE

To determine the time to first report of signs of nicotine dependence among youth exclusive e-cigarette users and compare this time to that for exclusive cigarette users.

METHODS

Secondary analysis of data (Waves 1-5; 2013-2019) from the Population Assessment of Tobacco and Health was conducted. Youth never tobacco users in the United States who reported exclusive past-30-day (P30D) e-cigarette or cigarette use (n = 2940, N = 5,391,642) in at least one wave were included in the current analysis. Survival analysis was used to estimate the time to the first report of three nicotine dependence indicators (i.e., "use within 30 minutes of waking"; "cravings" and "really needing to use") following the first report of P30D use. Multivariable Cox proportional hazard models were used to estimate adjusted hazard ratios (aHR).

RESULTS

There were no significant differences in the time to first report of "use within 30 minutes of waking" (aHR = 1.1, 95% CI = 0.87-1.40) and "cravings" (aHR = 1.09, 95% CI = 0.81-1.47) between exclusive P30D e-cigarette use and exclusive P30D cigarette use. However, compared to exclusive P30D e-cigarette use, the hazard of first reporting "really needing to use" tobacco was 39% (aHR 1.39; 95% CI: 1.05-1.84) times higher for those who reported exclusive P30D cigarette use after controlling for covariates.

CONCLUSION

Compared to exclusive P30D cigarette use, no differences in the time to first report of signs of nicotine dependence ("use within 30 minutes" and "cravings") were observed among exclusive P30D e-cigarette users. Policymakers and regulatory agencies should consider this evidence when assessing the abuse liability of e-cigarette products.

A Comparison of Mental Health Symptoms among Adults Who Vape Nicotine, Cannabis, or Both

OBJECTIVES

Dual use of combustible cannabis and nicotine is related to worse mental health symptoms (MHS); however, little is known about MHS among those who vape cannabis and nicotine. The current study aimed to determine if dual use of cannabis and nicotine vapes is associated with worse MHS compared to single use and to identify correlates of MHS for dual users.

METHODS

We used Amazon Mechanical Turk to survey adults (N = 492) who used nicotine or cannabis vapes in the past 30 days on stress, anxiety, depression, vape use behaviors and sociodemographic information. We conducted hierarchical linear regressions to compare MHS between dual vs. single substance vape use and to identify correlates of MHS, including sociodemographic variables and vape use characteristics.

RESULTS

The final sample was 37.6% female, 87.6% White, and 11% Hispanic/Latinx with a mean age of 34.15 years. After controlling for sociodemographic characteristics and combustible product use, dual users had significantly higher mean MHS severity than single users. For dual users, younger age and being married were associated with higher symptoms of depression and stress. Holding a medical cannabis card was associated with higher anxiety symptoms.

CONCLUSION

The findings suggest that dual use of cannabis and nicotine vapes is associated with worse MHS severity compared to single substance use.

Electronic cigarettes for smoking cessation

BACKGROUND

Electronic cigarettes (ECs) are handheld electronic vaping devices which produce an aerosol by heating an e-liquid. People who smoke, healthcare providers and regulators want to know if ECs can help people quit smoking, and if they are safe to use for this purpose. This is a review update conducted as part of a living systematic review.

OBJECTIVES

To examine the safety, tolerability and effectiveness of using electronic cigarettes (ECs) to help people who smoke tobacco achieve long-term smoking abstinence, in comparison to non-nicotine EC, other smoking cessation treatments and no treatment.

SEARCH METHODS

We searched the Cochrane Tobacco Addiction Group's Specialized Register to 1 February 2023, and Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, Embase, and PsycINFO to 1 July 2023, and reference-checked and contacted study authors.

SELECTION CRITERIA

We included trials in which people who smoke were randomized to an EC or control condition. We also included uncontrolled intervention studies in which all participants received an EC intervention as these studies have the potential to provide further information on harms and longer-term use. Studies had to report an eligible outcome.

DATA COLLECTION AND ANALYSIS

We followed standard Cochrane methods for screening and data extraction. Critical outcomes were abstinence from smoking after at least six months, adverse events (AEs), and serious adverse events (SAEs). We used a fixed-effect Mantel-Haenszel model to calculate risk ratios (RRs) with a 95% confidence interval (CI) for dichotomous outcomes. For continuous outcomes, we calculated mean differences. Where appropriate, we pooled data in pairwise and network meta-analyses (NMA).

MAIN RESULTS

We included 88 completed studies (10 new to this update), representing 27,235 participants, of which 47 were randomized controlled trials (RCTs). Of the included studies, we rated ten (all but one contributing to our main comparisons) at low risk of bias overall, 58 at high risk overall (including all non-randomized studies), and the remainder at unclear risk. There is high certainty that nicotine EC increases quit rates compared to nicotine replacement therapy (NRT) (RR 1.59, 95% CI 1.29 to 1.93; I2 = 0%; 7 studies, 2544 participants). In absolute terms, this might translate to an additional four quitters per 100 (95% CI 2 to 6 more). There is moderate-certainty evidence (limited by imprecision) that the rate of occurrence of AEs is similar between groups (RR 1.03, 95% CI 0.91 to 1.17; I2 = 0%; 5 studies, 2052 participants). SAEs were rare, and there is insufficient evidence to determine whether rates differ between groups due to very serious imprecision (RR 1.20, 95% CI 0.90 to 1.60; I2 = 32%; 6 studies, 2761 participants; low-certainty evidence). There is moderate-certainty evidence, limited by imprecision, that nicotine EC increases quit rates compared to non-nicotine EC (RR 1.46, 95% CI 1.09 to 1.96; I2 = 4%; 6 studies, 1613 participants). In absolute terms, this might lead to an additional three quitters per 100 (95% CI 1 to 7 more). There is moderate-certainty evidence of no difference in the rate of AEs between these groups (RR 1.01, 95% CI 0.91 to 1.11; I2 = 0%; 5 studies, 1840 participants). There is insufficient evidence to determine whether rates of SAEs differ between groups, due to very serious imprecision (RR 1.00, 95% CI 0.56 to 1.79; I2 = 0%; 9 studies, 1412 participants; low-certainty evidence). Due to issues with risk of bias, there is low-certainty evidence that, compared to behavioural support only/no support, quit rates may be higher for participants randomized to nicotine EC (RR 1.88, 95% CI 1.56 to 2.25; I2 = 0%; 9 studies, 5024 participants). In absolute terms, this represents an additional four quitters per 100 (95% CI 2 to 5 more). There was some evidence that (non-serious) AEs may be more common in people randomized to nicotine EC (RR 1.22, 95% CI 1.12 to 1.32; I2 = 41%, low-certainty evidence; 4 studies, 765 participants) and, again, insufficient evidence to determine whether rates of SAEs differed between groups (RR 0.89, 95% CI 0.59 to 1.34; I2 = 23%; 10 studies, 3263 participants; very low-certainty evidence). Results from the NMA were consistent with those from pairwise meta-analyses for all critical outcomes, and there was no indication of inconsistency within the networks. Data from non-randomized studies were consistent with RCT data. The most commonly reported AEs were throat/mouth irritation, headache, cough, and nausea, which tended to dissipate with continued EC use. Very few studies reported data on other outcomes or comparisons, hence, evidence for these is limited, with CIs often encompassing both clinically significant harm and benefit.

AUTHORS' CONCLUSIONS

There is high-certainty evidence that ECs with nicotine increase quit rates compared to NRT and moderate-certainty evidence that they increase quit rates compared to ECs without nicotine. Evidence comparing nicotine EC with usual care/no treatment also suggests benefit, but is less certain due to risk of bias inherent in the study design. Confidence intervals were for the most part wide for data on AEs, SAEs and other safety markers, with no difference in AEs between nicotine and non-nicotine ECs nor between nicotine ECs and NRT. Overall incidence of SAEs was low across all study arms. We did not detect evidence of serious harm from nicotine EC, but the longest follow-up was two years and the number of studies was small. The main limitation of the evidence base remains imprecision due to the small number of RCTs, often with low event rates. Further RCTs are underway. To ensure the review continues to provide up-to-date information to decision-makers, this review is a living systematic review. We run searches monthly, with the review updated when relevant new evidence becomes available. Please refer to the Cochrane Database of Systematic Reviews for the review's current status.

The smoking and vaping model, A user-friendly model for examining the country-specific impact of nicotine VAPING product use: application to Germany

BACKGROUND

Simulation models play an increasingly important role in tobacco control. Models examining the impact of nicotine vaping products (NVPs) and smoking tend to be highly specialized and inaccessible. We present the Smoking and Vaping Model (SAVM),a user-friendly cohort-based simulation model, adaptable to any country, that projects the public health impact of smokers switching to NVPs.

METHODS

SAVM compares two scenarios. The No-NVP scenario projects smoking rates in the absence of NVPs using population projections, deaths rates, life expectancy, and smoking prevalence. The NVP scenario models vaping prevalence and its impact on smoking once NVPs became popular. NVP use impact is estimated as the difference in smoking- and vaping-attributable deaths (SVADs) and life-years lost (LYLs) between the No-NVP and NVP scenarios. We illustrate SAVM's adaptation to the German adult ages 18+ population, the Germany-SAVM by adjusting the model using population, mortality, smoking and NVP use data.

RESULTS

Assuming that the excess NVP mortality risk is 5% that of smoking, Germany-SAVM projected 4.7 million LYLs and almost 300,000 SVADs averted associated with NVP use from 2012 to 2060. Increasing the excess NVP mortality risk to 40% with other rates constant resulted in averted 2.8 million LYLs and 200,000 SVADs during the same period.

CONCLUSIONS

SAVM enables non-modelers, policymakers, and other stakeholders to analyze the potential population health effects of NVP use and public health interventions.

Human abuse liability assessment of e-cigarettes: Why, what and how?

Cigarette smoking is the world's leading cause of preventable death and disease. Alternative nicotine products such as e-cigarettes have tobacco harm reduction potential, by providing smokers with an alternative form of nicotine delivery but with either the reduced presence or absence of the numerous harmful chemicals found in combustible cigarette smoke. One aspect of importance in determining the potential of e-cigarettes to provide a viable alternative to combustible cigarettes for smokers is their ability to cause dependence, also known as their abuse liability. E-cigarettes with little or no abuse liability would be unlikely to be used as a substitute for cigarettes, whereas at least some degree of abuse liability is acknowledged as supportive both to aiding cigarette substitution or complete cessation and to preventing relapse. Given this link between abuse liability and substitution efficacy, human studies assessing the abuse liability of e-cigarettes are important to determine their true harm reduction potential. In this review, the concept of tobacco product abuse liability is discussed, along with the primary elements-pharmacokinetics and pharmacodynamics (subjective effects)-that need to be assessed to determine abuse liability. The review also presents a number of human abuse liability study design considerations and discusses what existing studies in the literature tell us about the abuse liability and harm reduction potential of e-cigarettes.

Do respiratory physicians not care about people who smoke?

Nicotine containing vapes (e-cigarettes) are an effective tool to support people who smoke to quit tobacco. Despite this clinicians are wary of promoting vaping to their patients due to concerns that there may not be 'enough' evidence and about youth uptake of vaping. In this opinion article we discuss clinicians' views of vaping and consider the implications that harm misperceptions may have for public health.

Reducing e-cigarette use among youth and young adults: evidence of the truth campaign's impact

BACKGROUND

Mass media campaigns have been shown to be effective in reducing cigarette use. However, evidence is limited for whether campaigns can shift e-cigarette use among youth and young adults (YYA). To assess the impact of the truth anti-e-cigarette campaign, which focused on the effects of vaping on mental health, this study examines the relationship between campaign awareness and e-cigarette behaviour among YYA.

METHODS

Data from weekly cross-sectional surveys of YYA aged 15-24 years from September 2021 to October 2022 were used for multilevel models assessing how weekly campaign awareness is related to intentions to use e-cigarettes and current e-cigarette use (past 30 days). Weekly campaign awareness was calculated by averaging individual-level awareness for each week. Control variables included individual-level campaign awareness, sociodemographics, perceived financial situation, parental smoking, sensation seeking, and mental health.

RESULTS

Weekly campaign awareness ranged from 50% to 78%, with most weeks (77%) being within 65% and 75% of weekly campaign awareness. At weekly awareness levels between 65% and 75%, there was a significant association with lower intentions to use e-cigarettes. A dose-response relationship was observed for current use: compared with weeks with lower (<65%) awareness, weeks with awareness of 65-70% had 14% lower odds of current use, weeks with 70-75% awareness had 16% lower odds and weeks with >75% weekly awareness had 18% lower odds (p=0.018, p=0.009 and p=0.007, respectively).

CONCLUSIONS

Findings from this analysis of weekly campaign awareness demonstrate that exposure to the truth anti-e-cigarette campaign is associated with significantly lower odds of intentions to use and current use of e-cigarette among YYA.

A Quick Method for the Determination of the Fraction of Freebase Nicotine in Electronic Cigarettes

Recently, many electronic cigarettes (ECIGs) manufacturers have begun offering e-liquids, known as "nicotine salts". These salts that have started gaining big popularity among users can be formed by adding weak acid to e-liquid mixtures consisting of propylene glycol (PG), vegetable glycerin (VG), flavors, and nicotine. The latter can exist in two forms: monoprotonated (mp) and freebase (fb) based on the pH of the matrix. Over the years, the determination of the fraction of fb was found important to policymakers as the prevalence of this form in ECIGs has been associated with the harshness sensory of inhalable aerosols. Liquid-liquid extraction (LLE), ¹H NMR, and Henderson-Hasselback have been developed to deduce the fraction of fb; however, these methods were found to be time-consuming and have shown some challenges mainly due to the presence of a non-aqueous matrix consisting of PG and VG. This paper presents a quick non-aqueous pH measurement-based method that allows a quick determination of the fraction fb by just measuring the pH and the dielectric constant of the e-liquid. Then, by inputting these values into an established mathematical relationship, the fraction fb can be deduced. The relationship between pH, dielectric constant, and fb relies on knowing the values of the acidity dissociation constants of nicotine, which were determined for the first time in various PG/VG mixtures using a non-aqueous potentiometric titration. To validate the proposed method, the fraction fb was determined for commercials and lab-made nicotine salts utilizing the pH and LLE methods. The variation between the two methods was (<8.0%) for commercial e-liquids and lab-made nicotine salts containing lactic acid and salicylic acid. A larger discrepancy of up to 22% was observed for lab-made nicotine salts containing benzoic acid, which can be attributed to the stronger affinity of benzoic acid to toluene in the LLE method.

Single cell RNA-sequencing of human precision-cut lung slices: A novel approach to study the effect of vaping and viral infection on lung health

Vaping is an increasing health threat in the US and worldwide. The damaging impact of vaping on the human distal lung has been highlighted by the recent epidemic of electronic cigarette or vaping use-associated lung injury (EVALI). The pathogenesis of EVALI remains incompletely understood, due to a paucity of models that recapitulate the structural and functional complexity of the human distal lung and the still poorly defined culprit exposures to vaping products and respiratory viral infections. Our aim was to establish the feasibility of using single cell RNA-sequencing (scRNA-seq) technology in human precision-cut lung slices (PCLS) as a more physiologically relevant model to better understand how vaping regulates the antiviral and pro-inflammatory response to influenza A virus infection. Normal healthy donor PCLS were treated with vaping extract and influenza A viruses for scRNA-seq analysis. Vaping extract augmented host antiviral and pro-inflammatory responses in structural cells such as lung epithelial cells and fibroblasts, as well as in immune cells such as macrophages and monocytes. Our findings suggest that human distal lung slice model is useful to study the heterogeneous responses of immune and structural cells under EVALI conditions, such as vaping and respiratory viral infection.

Nicotine promotes e-cigarette vapour-induced lung inflammation and structural alterations

BACKGROUND

Electronic cigarette (e-cigarette) vapour is gaining popularity as an alternative to tobacco smoking and can induce acute lung injury. However, the specific role of nicotine in e-cigarette vapour and its long-term effects on the airways, lung parenchyma and vasculature remain unclear.

RESULTS

In vitro exposure to nicotine-containing e-cigarette vapour extract (ECVE) or to nicotine-free e-cigarette vapour extract (NF ECVE) induced changes in gene expression of epithelial cells and pulmonary arterial smooth muscle cells (PASMCs), but ECVE in particular caused functional alterations (e.g. a decrease in human and mouse PASMC proliferation by 29.3±5.3% and 44.3±8.4%, respectively). Additionally, acute inhalation of nicotine-containing e-cigarette vapour (ECV) but not nicotine-free e-cigarette vapour (NF ECV) increased pulmonary endothelial permeability in isolated lungs. Long-term in vivo exposure of mice to ECV for 8 months significantly increased the number of inflammatory cells, in particular lymphocytes, compared to control and NF ECV in the bronchoalveolar fluid (BALF) (ECV: 853.4±150.8 cells·mL-1; control: 37.0±21.1 cells·mL-1; NF ECV: 198.6±94.9 cells·mL-1) and in lung tissue (ECV: 25.7±3.3 cells·mm-3; control: 4.8±1.1 cells·mm-3; NF ECV: 14.1±2.2 cells·mm-3). BALF cytokines were predominantly increased by ECV. Moreover, ECV caused significant changes in lung structure and function (e.g. increase in airspace by 17.5±1.4% compared to control), similar to mild tobacco smoke-induced alterations, which also could be detected in the NF ECV group, albeit to a lesser degree. In contrast, the pulmonary vasculature was not significantly affected by ECV or NF ECV.

CONCLUSIONS

NF ECV components induce cell type-specific effects and mild pulmonary alterations, while inclusion of nicotine induces significant endothelial damage, inflammation and parenchymal alterations.

The risk profile of electronic nicotine delivery systems, compared to traditional cigarettes, on oral disease: a review

The use of electronic nicotine delivery systems (ENDS) has exploded, especially among teenagers and new smokers, amid widespread awareness of the dangers of traditional tobacco and restrictions on smoking. However, the risk effects of ENDS on physical health, especially oral health, are still ambiguous. The purpose of this study was to review the available evidence on risks of ENDS on oral health, and compares the differences between ENDS and traditional cigarettes. For heavy smokers, transferring the addiction of tobacco to ENDS can be less harmful to periodontal condition and physical health but is not completely without risk. The components of ENDS vapor have cytotoxic, genotoxic, and carcinogenic properties, and its usage may be associated with a wide range of oral health sequelae. The chemicals in ENDS increase the susceptibility to tooth decay, increase the risk of periodontal disease, peri-implant, and oral mucosal lesions. Nicotine aerosols from ENDS can be a potential risk factor for oral cancer due to the presence of carcinogenic components. Compared to smoking traditional cigarettes, the harm associated with ENDS use may be underestimated due to the reduced ability to control vaping behavior, ease of ENDS access, fewer vaping area restrictions, and better taste. Currently, the available evidence suggests that ENDS may be a safer alternative to traditional tobacco products. Though most oral symptoms experienced by ENDS users are relatively mild and temporary compared to traditional cigarettes, the dangers of ENDS still exist. However, further research with longer follow-up periods is required to establish the long-term safety of ENDS.

Electronic cigarettes and health outcomes: umbrella and systematic review of the global evidence

OBJECTIVE

To review and synthesise the global evidence regarding the health effects of electronic cigarettes (e-cigarettes, vapes).

STUDY DESIGN

Umbrella review (based on major independent reviews, including the 2018 United States National Academies of Sciences, Engineering, and Medicine [NASEM] report) and top-up systematic review of published, peer-reviewed studies in humans examining the relationship of e-cigarette use to health outcomes published since the NASEM report.

DATA SOURCES

Umbrella review: eight major independent reviews published 2017-2021. Systematic review: PubMed, MEDLINE, Scopus, Web of Science, the Cochrane Library, and PsycINFO (articles published July 2017 - July 2020 and not included in NASEM review).

DATA SYNTHESIS

Four hundred eligible publications were included in our synthesis: 112 from the NASEM review, 189 from our top-up review search, and 99 further publications cited by other reviews. There is conclusive evidence linking e-cigarette use with poisoning, immediate inhalation toxicity (including seizures), and e-cigarette or vaping product use-associated lung injury (EVALI; largely but not exclusively for e-liquids containing tetrahydrocannabinol and vitamin E acetate), as well as for malfunctioning devices causing injuries and burns. Environmental effects include waste, fires, and generation of indoor airborne particulate matter (substantial to conclusive evidence). There is substantial evidence that nicotine e-cigarettes can cause dependence or addiction in non-smokers, and strong evidence that young non-smokers who use e-cigarettes are more likely than non-users to initiate smoking and to become regular smokers. There is limited evidence that freebase nicotine e-cigarettes used with clinical support are efficacious aids for smoking cessation. Evidence regarding effects on other clinical outcomes, including cardiovascular disease, cancer, development, and mental and reproductive health, is insufficient or unavailable.

CONCLUSION

E-cigarettes can be harmful to health, particularly for non-smokers and children, adolescents, and young adults. Their effects on many important health outcomes are uncertain. E-cigarettes may be beneficial for smokers who use them to completely and promptly quit smoking, but they are not currently approved smoking cessation aids. Better quality evidence is needed regarding the health impact of e-cigarette use, their safety and efficacy for smoking cessation, and effective regulation.

REGISTRATION

Systematic review: PROSPERO, CRD42020200673 (prospective).

Electronic Cigarette Exposure Increases the Severity of Influenza a Virus Infection via TRAIL Dysregulation in Human Precision-Cut Lung Slices

The use of electronic nicotine dispensing systems (ENDS), also known as electronic cigarettes (ECs), is common among adolescents and young adults with limited knowledge about the detrimental effects on lung health such as respiratory viral infections and underlying mechanisms. Tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL), a protein of the TNF family involved in cell apoptosis, is upregulated in COPD patients and during influenza A virus (IAV) infections, but its role in viral infection during EC exposures remains unclear. This study was aimed to investigate the effect of ECs on viral infection and TRAIL release in a human lung precision-cut lung slices (PCLS) model, and the role of TRAIL in regulating IAV infection. PCLS prepared from lungs of nonsmoker healthy human donors were exposed to EC juice (E-juice) and IAV for up to 3 days during which viral load, TRAIL, lactate dehydrogenase (LDH), and TNF-α in the tissue and supernatants were determined. TRAIL neutralizing antibody and recombinant TRAIL were utilized to determine the contribution of TRAIL to viral infection during EC exposures. E-juice increased viral load, TRAIL, TNF-α release and cytotoxicity in IAV-infected PCLS. TRAIL neutralizing antibody increased tissue viral load but reduced viral release into supernatants. Conversely, recombinant TRAIL decreased tissue viral load but increased viral release into supernatants. Further, recombinant TRAIL enhanced the expression of interferon-β and interferon-λ induced by E-juice exposure in IAV-infected PCLS. Our results suggest that EC exposure in human distal lungs amplifies viral infection and TRAIL release, and that TRAIL may serve as a mechanism to regulate viral infection. Appropriate levels of TRAIL may be important to control IAV infection in EC users.

Differential Effects of Nicotine, Alcohol, and Coexposure on Neuroimmune-Related Protein and Gene Expression in Corticolimbic Brain Regions of Rats

Nicotine and alcohol co-use is extremely common and their use constitutes two of the most common causes of preventable death, yet the underlying biological mechanisms are largely understudied. Activation of neuroimmune toll-like receptors (TLRs) promotes the induction of proinflammatory cascades and increases alcohol intake in rodents, which further promotes TLRs in the brain; nicotine may decrease central proinflammatory signaling. The current studies sought to determine the effects of nicotine ± alcohol (alone or in combination) on circulating blood plasma and TLR protein/gene expression in addiction-associated corticolimbic brain regions, including the prefrontal cortex-prelimbic (mPFC-PL) and nucleus accumbens core (AcbC). Adult rats were treated with alcohol (0 or 2 g/kg, IG) and exposed to nicotine vapor (0 or 30 mg/mL solution) daily for 2, 14, or 28 days. Plasma studies indicated no effects of independent exposure or coexposure in males. Coexposure decreased plasma nicotine levels versus nicotine-only treated females, yet alcohol and cotinine concentrations were unchanged. By 28 days, the anti-inflammatory cytokine IL-13 was decreased in alcohol-only females. Divergent changes in TLR3 (but not TLR4) protein occurred for independent-drug exposed males (but not coexposure), with reductions in the mPFC-PL after 14 days and increases in the AcbC by 28 days. Gene expression following chronic coexposure suggests nicotine may regionally counteract alcohol-induced inflammation, including increased AcbC-TLR3/4/7 and several downstream markers in females and increased mPFC-PL-TLR3 and -STAT3 (but not IRF3) evident in males with exposure to either drug alone. These findings give further insight into the role of sex and the neuroimmune system in independent exposure and coexposure to nicotine ± alcohol.

Evaluation of the Psychometric Properties of Dependence Measures for Exclusive Electronic Cigarette Users

INTRODUCTION

Extant electronic cigarette (ECIG) dependence measures are largely adapted from those designed for cigarette smoking, though few have been evaluated for their psychometric properties.

AIMS AND METHODS

Never-smoking ECIG users (N = 134) participating in an online survey completed four dependence measures: Penn state electronic cigarette dependence index (PSECDI), e-cigarette dependence scale (EDS-4), diagnostic and statistical manual for tobacco use disorder (DSM-5), and Glover Nilsson behavioral questionnaire (GNBQ). They also reported on their ECIG use characteristics (eg, behaviors and reasons).

RESULTS

Internal consistency was highest for the EDS-4 (Cronbach's α = 0.88) followed by the GNBQ (α = 0.75), PSECDI (α = 0.72), and DSM (α = 0.71). Confirmatory factor analyses revealed a single-factor structure for the PSECDI, EDS-4, and GNBQ. For the DSM-5, however, two items did not load significantly (ECIG use interferes with responsibilities; reduce/give up activities because of ECIG use). Significant correlations were observed between all measures and the number of ECIG use days/week and/or years using ECIGs, as well as between DSM-5 scores and the number of ECIG quit attempts and initiation age. Endorsement of using ECIGs because "I like flavors" was correlated positively with DSM-5 and GNBQ scores.

CONCLUSIONS

All dependence measures evaluated herein demonstrated adequate reliability and construct validity. Future work should focus on determining which aspects of dependence are those that are unique to ECIG use, and subsequently developing a more comprehensive measure of ECIG dependence.

IMPLICATIONS

The measures assessed herein-PSECDI, EDS-4, DSM-5, and GNBQ-demonstrated adequate to good reliability and construct validity among a sample of never-smoking ECIG users. The dependence domains covered across measures were related yet distinct. Findings demonstrate the need for future evaluation of these different domains to determine which are the most salient characteristics of ECIG dependence.

Changes in Nicotine Dependence Among Smokers Using Electronic Cigarettes to Reduce Cigarette Smoking in a Randomized Controlled Trial

INTRODUCTION

How nicotine dependence will be affected when current smokers initiate electronic cigarette (e-cigarette) use to reduce cigarette smoking is unknown. This study evaluated cigarette, e-cigarette, and total nicotine dependence more than 6 months among smokers reducing cigarette consumption by replacing with e-cigarettes.

AIMS AND METHODS

Adult cigarette smokers were randomized to one of four conditions (36 mg/ml e-cigarette, 8 mg/ml e-cigarette, 0 mg/ml e-cigarette, or cigarette-substitute [CS] [provided at no cost]) and instructed to reduce their cigarette smoking by 75% at 1 month. Participants completed follow-up at 1, 3, and 6 months. The Penn State Nicotine Dependence Index (PSNDI) measured dependence on cigarettes (PSCDI) and e-cigarettes (PSECDI). Urine cotinine measured total nicotine exposure. Linear mixed effects models for each outcome were conducted and included interaction terms between visit and condition.

RESULTS

Participants (n = 520) were 58.8% female, 67.3% White, and 48.0 years old. At baseline, the median number of cigarettes smoked per day was 17.3 and the mean PSCDI score was 13.4, with no significant differences between conditions. Participants in the e-cigarette conditions reported significantly lower PSCDI scores, compared with baseline, and with the CS condition at all follow-up visits. Those in the 36 mg/ml e-cigarette condition reported greater PSECDI scores at 6 months, compared with baseline and the 0 mg/ml and 8 mg/ml conditions. At all follow-up visits, there were no differences in total nicotine exposure compared to baseline, nor between any conditions.

CONCLUSIONS

E-cigarette use was associated with reduced cigarette dependence, compared to the CS, without significant increases in total nicotine exposure.

IMPLICATIONS

Initiation of electronic cigarette use while continuing to smoke could potentially increase nicotine dependence. In this randomized trial aimed at helping smokers to reduce their cigarette intake, we found that use of an e-cigarette was associated with a reduction in cigarette dependence and an increase in e-cigarette dependence (in the condition with the highest nicotine concentration only), with no long term increase in total nicotine dependence or nicotine exposure.

Part one: abuse liability of Vuse Solo (G2) electronic nicotine delivery system relative to combustible cigarettes and nicotine gum

Abuse liability (AL) of electronic nicotine delivery systems (ENDS) is relevant as the category increases in popularity as a potentially less-harmful alternative to cigarette smoking. AL assessments are important to the FDA in determining if a new product is appropriate for the protection of public health. This paper reports the results for Vuse Solo (G2 cartridge design) compared to high and low AL-comparators evaluated in an open-label, randomized crossover confinement AL study. The confinement design was adapted from previous ambulatory studies of Vuse Solo (G1 cartridge design) and included product familiarization sessions before each four-hour test session in which subjective measures, nicotine pharmacokinetics (PK), and physiological endpoints were assessed following a single 10-min ad libitum product use session. Product liking, intent to use again, suppression of urge to smoke, and nicotine PK were lower after use of Vuse Solo compared to cigarettes and higher after use of Vuse Solo compared to nicotine gum. No significant differences in blood pressure or heart rate were observed between the products pre- to post-product use. These data reinforce previous research and provide the scientific evidence to support regulatory decisions demonstrating that Vuse Solo has an AL profile lower than that of combustible cigarettes but higher than that of nicotine gum and, therefore, may be a suitable replacement for cigarette smoking for some adult smokers.

Part three: a randomized study to assess biomarker changes in cigarette smokers switched to Vuse Solo or Abstinence

Biomarkers of exposure (BoE) can help evaluate exposure to combustion-related, tobacco-specific toxicants after smokers switch from cigarettes to potentially less-harmful products like electronic nicotine delivery systems (ENDS). This paper reports data for one (Vuse Solo Original) of three products evaluated in a randomized, controlled, confinement study of BoE in smokers switched to ENDS. Subjects smoked their usual brand cigarette ad libitum for two days, then were randomized to one of three ENDS for a 7-day ad libitum use period, or to smoking abstinence. Thirteen BoE were assessed at baseline and Day 5, and percent change in mean values for each BoE was calculated. Biomarkers of potential harm (BoPH) linked to oxidative stress, platelet activation, and inflammation were also assessed. Levels decreased among subjects randomized to Vuse Solo versus Abstinence, respectively, for the following BoE: 42-96% versus 52-97% (non-nicotine constituents); 51% versus 55% (blood carboxyhemoglobin); and 29% versus 96% (nicotine exposure). Significant decreases were observed in three BoPH: leukotriene E4, 11-dehydro-thromboxane B2, and 2,3-dinor thromboxane B2 on Day 7 in the Vuse Solo and Abstinence groups. These findings show that ENDS use results in substantially reduced exposure to toxicants compared to smoking, which may lead to reduced biological effects.

Electronic cigarettes for smoking cessation

BACKGROUND

Electronic cigarettes (ECs) are handheld electronic vaping devices which produce an aerosol by heating an e-liquid. Some people who smoke use ECs to stop or reduce smoking, although some organizations, advocacy groups and policymakers have discouraged this, citing lack of evidence of efficacy and safety. People who smoke, healthcare providers and regulators want to know if ECs can help people quit smoking, and if they are safe to use for this purpose. This is a review update conducted as part of a living systematic review.

OBJECTIVES

To examine the effectiveness, tolerability, and safety of using electronic cigarettes (ECs) to help people who smoke tobacco achieve long-term smoking abstinence.

SEARCH METHODS

We searched the Cochrane Tobacco Addiction Group's Specialized Register, the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, Embase, and PsycINFO to 1 July 2022, and reference-checked and contacted study authors.  SELECTION CRITERIA: We included randomized controlled trials (RCTs) and randomized cross-over trials, in which people who smoke were randomized to an EC or control condition. We also included uncontrolled intervention studies in which all participants received an EC intervention. Studies had to report abstinence from cigarettes at six months or longer or data on safety markers at one week or longer, or both.

DATA COLLECTION AND ANALYSIS

We followed standard Cochrane methods for screening and data extraction. Our primary outcome measures were abstinence from smoking after at least six months follow-up, adverse events (AEs), and serious adverse events (SAEs). Secondary outcomes included the proportion of people still using study product (EC or pharmacotherapy) at six or more months after randomization or starting EC use, changes in carbon monoxide (CO), blood pressure (BP), heart rate, arterial oxygen saturation, lung function, and levels of carcinogens or toxicants, or both. We used a fixed-effect Mantel-Haenszel model to calculate risk ratios (RRs) with a 95% confidence interval (CI) for dichotomous outcomes. For continuous outcomes, we calculated mean differences. Where appropriate, we pooled data in meta-analyses.

MAIN RESULTS

We included 78 completed studies, representing 22,052 participants, of which 40 were RCTs. Seventeen of the 78 included studies were new to this review update. Of the included studies, we rated ten (all but one contributing to our main comparisons) at low risk of bias overall, 50 at high risk overall (including all non-randomized studies), and the remainder at unclear risk. There was high certainty that quit rates were higher in people randomized to nicotine EC than in those randomized to nicotine replacement therapy (NRT) (RR 1.63, 95% CI 1.30 to 2.04; I2 = 10%; 6 studies, 2378 participants). In absolute terms, this might translate to an additional four quitters per 100 (95% CI 2 to 6). There was moderate-certainty evidence (limited by imprecision) that the rate of occurrence of AEs was similar between groups (RR 1.02, 95% CI 0.88 to 1.19; I2 = 0%; 4 studies, 1702 participants). SAEs were rare, but there was insufficient evidence to determine whether rates differed between groups due to very serious imprecision (RR 1.12, 95% CI 0.82 to 1.52; I2 = 34%; 5 studies, 2411 participants). There was moderate-certainty evidence, limited by imprecision, that quit rates were higher in people randomized to nicotine EC than to non-nicotine EC (RR 1.94, 95% CI 1.21 to 3.13; I2 = 0%; 5 studies, 1447 participants). In absolute terms, this might lead to an additional seven quitters per 100 (95% CI 2 to 16). There was moderate-certainty evidence of no difference in the rate of AEs between these groups (RR 1.01, 95% CI 0.91 to 1.11; I2 = 0%; 5 studies, 1840 participants). There was insufficient evidence to determine whether rates of SAEs differed between groups, due to very serious imprecision (RR 1.00, 95% CI 0.56 to 1.79; I2 = 0%; 8 studies, 1272 participants). Compared to behavioural support only/no support, quit rates were higher for participants randomized to nicotine EC (RR 2.66, 95% CI 1.52 to 4.65; I2 = 0%; 7 studies, 3126 participants). In absolute terms, this represents an additional two quitters per 100 (95% CI 1 to 3). However, this finding was of very low certainty, due to issues with imprecision and risk of bias. There was some evidence that (non-serious) AEs were more common in people randomized to nicotine EC (RR 1.22, 95% CI 1.12 to 1.32; I2 = 41%, low certainty; 4 studies, 765 participants) and, again, insufficient evidence to determine whether rates of SAEs differed between groups (RR 1.03, 95% CI 0.54 to 1.97; I2 = 38%; 9 studies, 1993 participants).  Data from non-randomized studies were consistent with RCT data. The most commonly reported AEs were throat/mouth irritation, headache, cough, and nausea, which tended to dissipate with continued EC use. Very few studies reported data on other outcomes or comparisons, hence evidence for these is limited, with CIs often encompassing clinically significant harm and benefit.

AUTHORS' CONCLUSIONS

There is high-certainty evidence that ECs with nicotine increase quit rates compared to NRT and moderate-certainty evidence that they increase quit rates compared to ECs without nicotine. Evidence comparing nicotine EC with usual care/no treatment also suggests benefit, but is less certain. More studies are needed to confirm the effect size. Confidence intervals were for the most part wide for data on AEs, SAEs and other safety markers, with no difference in AEs between nicotine and non-nicotine ECs nor between nicotine ECs and NRT. Overall incidence of SAEs was low across all study arms. We did not detect evidence of serious harm from nicotine EC, but longest follow-up was two years and the number of studies was small. The main limitation of the evidence base remains imprecision due to the small number of RCTs, often with low event rates, but further RCTs are underway. To ensure the review continues to provide up-to-date information to decision-makers, this review is a living systematic review. We run searches monthly, with the review updated when relevant new evidence becomes available. Please refer to the Cochrane Database of Systematic Reviews for the review's current status.

Differences in cigarette smoking quit attempts and cessation between adults who did and did not take up nicotine vaping: Findings from the ITC four country smoking and vaping surveys

INTRODUCTION

There is mixed evidence as to whether nicotine vaping products (NVPs) can help adults who smoke transition away from cigarettes. This study investigated if self-reported attempts to quit smoking and smoking cessation, over a period of either 18 or 24 months, differed between respondents who initiated nicotine vaping versus those who did not. Outcome comparisons were made between those who: (1) initiated vaping vs. those who did not; (2) initiated daily or non-daily vaping vs. those who did not; and (3) initiated daily or non-daily vaping between surveys and continued to vape at follow-up (daily or non-daily) vs. those who did not initiate vaping.

METHODS

This cohort study included 3516 respondents from the ITC Four Country Smoking and Vaping Surveys (Australia, Canada, England, United Sates), recruited at Wave 1 (2016) or 2 (2018) and followed up at Wave 2 (18 months) and/or 3 (2020, 24 months). Adults who smoked daily at baseline and did not have a history of regular vaping were included. Initiation of vaping was defined as beginning to vape at least monthly between surveys. Respondents indicated whether they made an attempt to quit smoking between surveys. Smoking cessation was defined as those who self-reported no longer smoking cigarettes at follow-up.

RESULTS

Relative to those who did not initiate vaping, initiation of any daily vaping between surveys was associated with a greater likelihood of smokers making a cigarette quit attempt (p < 0.001) and quitting smoking (p < 0.001). Among smokers who attempted to quit smoking, initiation of daily vaping was associated with a greater likelihood of being abstinent from smoking at follow-up (p = 0.001). Respondents who initiated vaping between surveys and were vaping daily at follow up were significantly more likely to have attempted to quit smoking (p < 0.001) and to have quit smoking (p < 0.001) than those who did not initiate vaping. Respondents who initiated non-daily vaping did not differ significantly from those who did not initiate vaping on any of the outcome measures.

CONCLUSIONS

Daily NVP use was associated with increased attempts to quit smoking and abstinence from smoking cigarettes. These findings are consistent with the concept that complete cigarette substitution may be more likely to be achieved when smokers vape nicotine daily.

Electronic cigarette vapor exposure exaggerates the pro-inflammatory response during influenza A viral infection in human distal airway epithelium

Electronic cigarettes or vaping products have been marketed as a safer alternative to smoking, but very little is known about the health effects in the human lung, particularly in the distal airways, a key site of airway obstruction and destruction in chronic obstructive pulmonary disease that is often exacerbated by viral infections. The aim of this study was to investigate the effects of electronic cigarette vapor (e-vapor) on human distal airway epithelial responses to influenza A virus (IAV) infection. We isolated primary small airway epithelial cells (SAECs) from donor lungs free of lung disease, and cultured them at air-liquid interface (ALI). To measure markers of epithelial injury such as integrity of epithelial barrier structure and function, we selected a regimen of non-toxic, barrier preserving e-vapor exposure of cultured cells to 15 puffs of e-vapor from a commercially available e-cigarette once per day for 3 days, prior to IAV infection. After 72 h of infection, media and cell lysates were collected to measure cytokines involved in inflammatory and antiviral responses. Pre-exposure to e-vapor with IAV infection, compared to IAV infection alone, significantly increased inflammatory and antiviral mediators including IL-8, CXCL10, IFN-beta, and MX1. Our results suggest that e-vapor exposure amplifies human distal airway pro-inflammatory response to IAV infection, independently of the severity of cell injury during viral infection.

Cardiopulmonary Consequences of Vaping in Adolescents: A Scientific Statement From the American Heart Association

Although the US Food and Drug Administration has not approved e-cigarettes as a cessation aid, industry has at times positioned their products in that way for adults trying to quit traditional cigarettes; however, their novelty and customizability have driven them into the hands of unintended users, particularly adolescents. Most new users of e-cigarette products have never smoked traditional cigarettes; therefore, understanding the respiratory and cardiovascular consequences of e-cigarette use has become of increasing interest to the research community. Most studies have been performed on adult e-cigarette users, but the majority of these study participants are either former traditional smokers or smokers who have used e-cigarettes to switch from traditional smoking. Therefore, the respiratory and cardiovascular consequences in this population are not attributable to e-cigarette use alone. Preclinical studies have been used to study the effects of naive e-cigarette use on various organ systems; however, almost all of these studies have used adult animals, which makes translation of health effects to adolescents problematic. Given that inhalation of any foreign substance can have effects on the respiratory and cardiovascular systems, a more holistic understanding of the pathways involved in toxicity could help to guide researchers to novel therapeutic treatment strategies. The goals of this scientific statement are to provide salient background information on the cardiopulmonary consequences of e-cigarette use (vaping) in adolescents, to guide therapeutic and preventive strategies and future research directions, and to inform public policymakers on the risks, both short and long term, of vaping.

A randomised, crossover, clinical study to assess nicotine pharmacokinetics and subjective effects of the BIDI® stick ENDS compared with combustible cigarettes and a comparator ENDS in adult smokers

BACKGROUND

Nicotine pharmacokinetic assessments of electronic nicotine delivery systems (ENDS) are crucial to understand their ability to provide an alternative to cigarette smoking. Subjective effects data also strongly contribute to this understanding. The BIDI® Stick is a disposable ENDS product which contains 59 mg/ml nicotine benzoate salt and various flavours.

METHODS

In this study, we assessed nicotine pharmacokinetics and subjective effects of 6 flavour variants of BIDI® Stick ENDS in adult smokers, compared to cigarettes and a comparator ENDS product. During each of eight study visits, 18 volunteer smoker subjects randomly used one of either their usual brand (UB) of cigarette, a BIDI® Stick ENDS, or a comparator ENDS (JUUL 59 mg/ml nicotine with Virginia Tobacco flavour), during both controlled (10 puffs, 30 s apart) and ad libitum (60 min) puffing sessions. Blood samples were collected at various time points and subjective effects questionnaires were administered.

RESULTS

Mean [SD] plasma nicotine Cmax 0-120 was not significantly different between BIDI® Stick ENDS with any flavour (range 15.3 [9.90] ng/ml for BIDI® Stick Winter to 17.6 [9.00] ng/ml for BIDI® Stick Classic) and UB cigarettes (16.2 [9.17] ng/ml). Mean [SD] AUC0-120 (range 569.7 [327.29] to 628.6 [408.99]  min*ng/ml for BIDI® Stick ENDS and 747.1 [325.48]  min*ng/ml for UB cigarettes) and median Tmax 0-120 (range 5-7 min for all BIDI® Stick ENDS and UB cigarettes) values were also not significantly different between BIDI® Stick ENDS and UB cigarettes, while subjective effects measures were also similar between BIDI® Stick ENDS and UB cigarettes. Mean [SD] plasma nicotine Cmax 0-120, AUC0-120, and median Tmax 0-120 were 6.8 [4.13] ng/ml, 243.6 [179.04] min*ng/ml, and 5 min, respectively, for JUUL ENDS. These values were significantly different compared with those for all BIDI® Stick ENDS and UB cigarettes for both Cmax 0-120 and AUC0-120 but not for Tmax 0-120.

CONCLUSIONS

BIDI® Stick ENDS delivered nicotine to users comparably to their UB combustible cigarette and higher than JUUL ENDS, and also elicited similar subjective effects such as satisfaction and relief. Thus, the BIDI® Stick ENDS may be a satisfying alternative to cigarettes among current smokers and may support their transitioning away from cigarette smoking.

TRIAL REGISTRATION

ClinicalTrials.gov (identifier number NCT05072925).

Electronic Cigarette Vaping Did Not Enhance the Neural Process of Working Memory for Regular Cigarette Smokers

Background

Electronic cigarettes (e-cigs) as substitute devices for regular tobacco cigarettes (r-cigs) have been increasing in recent times. We investigated neuronal substrates of vaping e-cigs and smoking r-cigs from r-cig smokers.

Methods

Twenty-two r-cig smokers made two visits following overnight smoking cessation. Functional magnetic resonance imaging (fMRI) data were acquired while participants watched smoking images. Participants were then allowed to smoke either an e-cig or r-cig until satiated and fMRI data were acquired. Their craving levels and performance on the Montreal Imaging Stress Task and a 3-back alphabet/digit recognition task were obtained and analyzed using two-way repeated-measures analysis of variance. Regions-of-interest (ROIs) were identified by comparing the abstained and satiated conditions. Neuronal activation within ROIs was regressed on the craving and behavioral data separately.

Results

Craving was more substantially reduced by smoking r-cigs than by vaping e-cigs. The response time (RT) for the 3-back task was significantly shorter following smoking r-cigs than following vaping e-cigs (interaction: F (1, 17) = 5.3, p = 0.035). Neuronal activations of the right vermis (r = 0.43, p = 0.037, CI = [-0.05, 0.74]), right caudate (r = 0.51, p = 0.015, CI = [0.05, 0.79]), and right superior frontal gyrus (r = −0.70, p = 0.001, CI = [−0.88, −0.34]) were significantly correlated with the RT for the 3-back task only for smoking r-cigs.

Conclusion

Our findings suggest that insufficient satiety from vaping e-cigs for r-cigs smokers may be insignificant effect on working memory function.

An Examination Perceptions of Similarity to Cigarettes, Health Risk Perceptions, and Willingness to Try Across Nicotine Vaping Products

INTRODUCTION

This brief report examines how e-cigarette form affects perceptions of cigarette similarity, health risk evaluations, and willingness to try the product. The mediating roles of product form similarity to combustible cigarettes and perceived health risk across vapers and non-vapers are also assessed.

METHODS

A between-subjects experiment examines the effects of four product forms (a cigalike, a vape pen, a tank, and a pod/Juul) for 443 nonsmokers who are either current vapers or non-vapers. Multi-item measures are used to assess the mediating and outcome dependent measures.

RESULTS

Results show that the product form affects similarity, and there are differences between vapers and non-vapers for all outcomes. Moderated mediation results show that (1) form similarity mediates the effects on health perceptions and differs between vapers and non-vapers and (2) there are serial mediation effects of form on willingness to try the different products.

CONCLUSIONS

Electronic nicotine delivery systems (ENDS) product form matters. Similarity to combustible cigarettes influences health risk perceptions, and, in turn, there are effects on willingness to try the product. There are differences in mediation effects across current vapers and non-vapers. These results contribute to understanding reasons why the public health community should monitor and consider how manipulations in product form can affect and reduce health risk perceptions.

IMPLICATIONS

ENDS have evolved since their introduction to the market and are now comprised of product types that vary substantially in design and appearance. By changing form and reducing resemblance to cigarettes, these differences in product form are shown to have downstream consequences on health risk perceptions and willingness to try the product. The public health community needs to consider unconventional ways in which companies may reduce risk perceptions of youthful users and nonusers, even when there are no objective differences in risk across product types.

Efficacy of antimicrobial photodynamic therapy in reducing oral yeasts carriage among individuals using electronic nicotine delivery systems

OBJECTIVE

The aim was to assess the efficacy of antimicrobial photodynamic therapy (aPDT) in reducing oral yeasts carriage among individuals using electronic nicotine delivery systems (ENDS).

METHODS

Self-reported ENDS users and non-users (individuals that reported to have never used any nicotinic product) were included. Demographic data was collected using a questionnaire. Patients were divided into 2 subgroups: (a) aPDT group; and (b) sham aPDT group. aPDT was performed using a curcumin-based photosensitizer that was exposed to a central wavelength of 660 nm and an estimated average fluency of 200 J/cm2. The system delivered light by uniform diffusion for 5 minutes. Sham aPDT was performed using a non-activated laser tip. Oral yeasts colony forming units were determined using standard techniques. Oral yeasts were assessed at baseline and at 3-months of follow-up. Level of significance was set at P<0.05.

RESULTS

Twenty-three ENDS-users (19 males and 4 females) and 23 controls (17 males and 6 females) were included. ENDS-users were vaping for 8.3 ± 0.6 years and were using their ENDS devices 13.6 ± 2.7 times daily. Toothbrushing twice daily was reported by 8.7% and 21.7% of ENDS-users and controls, respectively. Tongue brushing was reported by none of the individuals. At baseline, oral yeasts CFU/ml were significantly higher among ENDS-users in the PDT (P<0.05) and sham PDT (P<0.05) groups compared with controls (Table 2; Figure 1). At 3-months of follow-up, CFU/ml were significantly higher among ENDS-users in the PDT (P<0.05) and sham PDT (P<0.05) groups compared with controls CONCLUSION: : A single session of aPDT is ineffective in reducing the oral yeasts CFU/ml in ENDS-users. Further studies are needed to assess the impact of multiple sessions of aPDT in reducing the oral yeasts CFU/ml in ENDS-users.

E-cigarette device and liquid characteristics and E-cigarette dependence: A pilot study of pod-based and disposable E-cigarette users

BACKGROUND

E-cigarette device and liquid characteristics, such as electrical power output and liquid nicotine concentration, determine the rate at which nicotine is emitted from the e-cigarette (i.e., nicotine flux), and thus are likely to influence user nicotine dependence. We hypothesize that nicotine flux would be associated with the E-cigarette Dependence Scale (EDS) among pod-based and disposable e-cigarette products.

METHODS

Data were obtained from online panel participants between 18 and 65 years of age, who had indicated that they were either former or current e-cigarette users and resided within the United States (N = 1036). To be included in these analyses, participants had to provide information regarding device type (pod-based or disposable), power (watts), and nicotine concentration (mg/mL), from which we could determine nicotine flux (µg/s) (N = 666). To assess the relationship between nicotine flux and EDS, a series of multivariable linear regressions were conducted. Each model was separated by device type and adjusted for by age and past 30-day e-cigarette use.

RESULTS

Greater nicotine flux was associated with higher EDS scores among pod-based e-cigarette users (beta = 0.19, SE = 0.09, p-value = 0.043), but not users of disposable e-cigarettes. Neither power nor nicotine concentration were associated with EDS scores among users of either e-cigarette device type.

CONCLUSION

Results support the hypothesis that nicotine flux is positively associated with nicotine dependence in a sample of current users of pod-based and disposable e-cigarettes.

Tracing the movement of electronic cigarette flavor chemicals and nicotine from refill fluids to aerosol, lungs, exhale, and the environment

BACKGROUND

Given the high concentrations of nicotine and flavor chemicals in EC (electronic cigarette) fluids, it is important to determine how efficiently they transfer to aerosols, how well they are retained by users (exposure), and if they are exhaled into the environment where they settle of surfaces forming ECEAR (EC exhaled aerosol residue).

OBJECTIVES

To quantify the flavor chemicals and nicotine in refill fluids, inhaled aerosols, and exhaled aerosols. Then deduce their retention and contribution to ECEAR.

METHODS

Flavor chemicals and nicotine were identified and quantified by GC-MS in two refill fluids, smoking machine-generated aerosols, and aerosols exhaled by 10 human participants (average age 21; 7 males). Machine generated aerosols were made with varying puff durations and two wattages (40 and 80). Participants generated exhale ad libitum; their exhale was quantified, and chemical retention and contribution to ECEAR was modeled.

RESULTS

"Dewberry Cream" had five dominant (≥1 mg/mL) flavor chemicals (maltol, ethyl maltol, vanillin, ethyl vanillin, furaneol), while "Cinnamon Roll" had one (cinnamaldehyde). Nicotine transferred well to aerosols irrespective of topography; however, transfer efficiencies of flavor chemicals depended on the chemical, puff volume, puff duration, pump head, and EC power. Participants could be classified as "mouth inhalers" or "lung inhalers" based on their exhale of flavor chemicals and nicotine and retention. Lung inhalers had high retention and exhaled low concentrations of EC chemicals. Only mouth inhalers exhaled sufficient concentrations of flavor chemicals/nicotine to contribute to chemical deposition on environmental surfaces (ECEAR).

CONCLUSION

These data help distinguish two types of EC users, add to our knowledge of chemical exposure during vaping, and provide information useful in regulating EC use.

Effect of Electronic Nicotine Delivery Systems on Cigarette Abstinence in Smokers with no Plans to Quit: Exploratory Analysis of a Randomized Placebo-Controlled Trial

INTRODUCTION

The extent to which use of electronic nicotine delivery systems (ENDS) for smoking reduction leads to cigarette abstinence in smokers with no plans to quit smoking is unclear. This exploratory analysis examined the effects of ENDS delivering different amounts of nicotine on cigarette abstinence up to 24-week follow-up, in comparison to placebo or a behavioral substitute.

METHODS

This four-arm parallel-group, randomized, placebo-controlled trial took place at two academic medical centers in USA (Penn State Hershey and Virginia Commonwealth University). Participants were current adult smokers (N=520) interested in reducing but not planning to quit. They received brief advice and were randomized to one of four 24-week conditions, receiving either an eGo-style ENDS paired with 0, 8 or 36 mg/ml nicotine liquid (double-blind) or a cigarette-shaped tube, as a cigarette substitute (CS). Self-reported daily cigarette consumption and exhaled carbon monoxide (CO) were measured at all study visits. Outcomes included intent-to-treat, self-reported 7-day cigarette abstinence, biochemically confirmed by exhaled CO at 24 weeks after randomization.

RESULTS

At 24 weeks, significantly more participants in the 36 mg/ml condition (14/130, 10.8%) than in the 0 mg/ml condition (1/130, 0.8%) and the CS condition (4/130, 3.1%) were abstinent (relative risk = 14 [95% CI=1.9-104.9] and 3.5 [95% CI=1.2-10.4], respectively). The abstinence rate in the 8 mg/ml condition was 4.6% (6/130).

CONCLUSIONS

When smokers seeking to reduce smoking tried ENDS, few quit smoking in the short term. However, if smokers continued to use an ENDS with cigarette-like nicotine delivery, a greater proportion completely switched to ENDS, as compared with placebo or a cigarette substitute.

IMPLICATIONS

The extent to which use of electronic nicotine delivery systems (ENDS) for smoking reduction leads to cigarette abstinence in smokers with no plans to quit smoking was unclear. This randomized trial found that ENDS with nicotine delivery approaching that of a cigarette are more effective in helping ambivalent smokers to quit cigarette smoking.

VAPIng into ARDS: Acute Respiratory Distress Syndrome and Cardiopulmonary Failure

"Modern" vaping involving battery-operated electronic devices began approximately one dozen years and has quickly evolved into a multibillion dollar industry providing products to an estimated 50 million users worldwide. Originally developed as an alternative to traditional cigarette smoking, vaping now appeals to a diverse demographic including substantial involvement of young people who often have never used cigarettes. The rapid rise of vaping fueled by multiple factors has understandably outpaced understanding of biological effects, made even more challenging due to wide ranging individual user habits and preferences. Consequently while vaping-related research gathers momentum, vaping-associated pathological injury (VAPI) has been established by clinical case reports with severe cases manifesting as acute respiratory distress syndrome (ARDS) with examples of right ventricular cardiac failure. Therefore, basic scientific studies are desperately needed to understand the impact of vaping upon the lungs as well as cardiopulmonary structure and function. Experimental models that capture fundamental characteristics of vaping-induced ARDS are essential to study pathogenesis and formulate recommendations to mitigate harmful effects attributable to ingredients or equipment. So too, treatment strategies to promote recovery from vaping-associated damage require development and testing at the preclinical level. This review summarizes the back story of vaping leading to present day conundrums with particular emphasis upon VAPI-associated ARDS and prioritization of research goals.

Electronic cigarettes for smoking cessation

BACKGROUND

Electronic cigarettes (ECs) are handheld electronic vaping devices which produce an aerosol formed by heating an e-liquid. Some people who smoke use ECs to stop or reduce smoking, but some organizations, advocacy groups and policymakers have discouraged this, citing lack of evidence of efficacy and safety. People who smoke, healthcare providers and regulators want to know if ECs can help people quit and if they are safe to use for this purpose. This is an update conducted as part of a living systematic review.

OBJECTIVES

To examine the effectiveness, tolerability, and safety of using electronic cigarettes (ECs) to help people who smoke tobacco achieve long-term smoking abstinence.

SEARCH METHODS

We searched the Cochrane Tobacco Addiction Group's Specialized Register, the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, Embase, and PsycINFO to 1 May 2021, and reference-checked and contacted study authors. We screened abstracts from the Society for Research on Nicotine and Tobacco (SRNT) 2021 Annual Meeting.   SELECTION CRITERIA: We included randomized controlled trials (RCTs) and randomized cross-over trials, in which people who smoke were randomized to an EC or control condition. We also included uncontrolled intervention studies in which all participants received an EC intervention. Studies had to report abstinence from cigarettes at six months or longer or data on safety markers at one week or longer, or both.

DATA COLLECTION AND ANALYSIS

We followed standard Cochrane methods for screening and data extraction. Our primary outcome measures were abstinence from smoking after at least six months follow-up, adverse events (AEs), and serious adverse events (SAEs). Secondary outcomes included the proportion of people still using study product (EC or pharmacotherapy) at six or more months after randomization or starting EC use, changes in carbon monoxide (CO), blood pressure (BP), heart rate, arterial oxygen saturation, lung function, and levels of carcinogens or toxicants or both. We used a fixed-effect Mantel-Haenszel model to calculate risk ratios (RRs) with a 95% confidence interval (CI) for dichotomous outcomes. For continuous outcomes, we calculated mean differences. Where appropriate, we pooled data in meta-analyses.

MAIN RESULTS

We included 61 completed studies, representing 16,759 participants, of which 34 were RCTs. Five of the 61 included studies were new to this review update. Of the included studies, we rated seven (all contributing to our main comparisons) at low risk of bias overall, 42 at high risk overall (including all non-randomized studies), and the remainder at unclear risk. There was moderate-certainty evidence, limited by imprecision, that quit rates were higher in people randomized to nicotine EC than in those randomized to nicotine replacement therapy (NRT) (risk ratio (RR) 1.53, 95% confidence interval (CI) 1.21 to 1.93; I2 = 0%; 4 studies, 1924 participants). In absolute terms, this might translate to an additional three quitters per 100 (95% CI 1 to 6). There was low-certainty evidence (limited by very serious imprecision) that the rate of occurrence of AEs was similar (RR 0.98, 95% CI 0.80 to 1.19; I2 = 0%; 2 studies, 485 participants). SAEs were rare, but there was insufficient evidence to determine whether rates differed between groups due to very serious imprecision (RR 1.30, 95% CI 0.89 to 1.90: I2 = 0; 4 studies, 1424 participants). There was moderate-certainty evidence, again limited by imprecision, that quit rates were higher in people randomized to nicotine EC than to non-nicotine EC (RR 1.94, 95% CI 1.21 to 3.13; I2 = 0%; 5 studies, 1447 participants). In absolute terms, this might lead to an additional seven quitters per 100 (95% CI 2 to 16). There was moderate-certainty evidence of no difference in the rate of AEs between these groups (RR 1.01, 95% CI 0.91 to 1.11; I2 = 0%; 3 studies, 601 participants). There was insufficient evidence to determine whether rates of SAEs differed between groups, due to very serious imprecision (RR 1.06, 95% CI 0.47 to 2.38; I2 = 0; 5 studies, 792 participants). Compared to behavioural support only/no support, quit rates were higher for participants randomized to nicotine EC (RR 2.61, 95% CI 1.44 to 4.74; I2 = 0%; 6 studies, 2886 participants). In absolute terms this represents an additional six quitters per 100 (95% CI 2 to 15). However, this finding was of very low certainty, due to issues with imprecision and risk of bias. There was some evidence that non-serious AEs were more common in people randomized to nicotine EC (RR 1.22, 95% CI 1.12 to 1.32; I2 = 41%, low certainty; 4 studies, 765 participants), and again, insufficient evidence to determine whether rates of SAEs differed between groups (RR 1.51, 95% CI 0.70 to 3.24; I2 = 0%; 7 studies, 1303 participants).  Data from non-randomized studies were consistent with RCT data. The most commonly reported AEs were throat/mouth irritation, headache, cough, and nausea, which tended to dissipate with continued use. Very few studies reported data on other outcomes or comparisons, hence evidence for these is limited, with CIs often encompassing clinically significant harm and benefit.

AUTHORS' CONCLUSIONS

There is moderate-certainty evidence that ECs with nicotine increase quit rates compared to NRT and compared to ECs without nicotine. Evidence comparing nicotine EC with usual care/no treatment also suggests benefit, but is less certain. More studies are needed to confirm the effect size. Confidence intervals were for the most part wide for data on AEs, SAEs and other safety markers, with no difference in AEs between nicotine and non-nicotine ECs. Overall incidence of SAEs was low across all study arms. We did not detect  evidence of harm from nicotine EC, but longest follow-up was two years and the  number of studies was small. The main limitation of the evidence base remains imprecision due to the small number of RCTs, often with low event rates, but further RCTs are underway. To ensure the review continues to provide up-to-date information to decision-makers, this review is now a living systematic review. We run searches monthly, with the review updated when relevant new evidence becomes available. Please refer to the Cochrane Database of Systematic Reviews for the review's current status.

Nicotine delivery and relief of craving after consumption of European JUUL e-cigarettes prior and after pod modification

The emergence of e-cigarettes on the consumer market led to a tremendous rise in e-cigarette consumption among adolescents in the United States. The success of JUUL and other pod systems was linked to its high nicotine delivery capacity. In compliance with the European Tobacco Product directive, liquid nicotine contents in the European JUUL variants are limited to 20 mg/mL or below. A short time after launching the initial version in Europe, JUUL pods have been modified in terms of the wick material used. This modification has been demonstrated previously to lead to an elevated aerosol generation, consequently, to a larger amount of nicotine per puff generated. The present study was designed to assess whether the mentioned differences between the "initial" and "modified" JUUL versions may cause a significant difference during consumption, and how nicotine delivery compares with tobacco cigarettes. In this single-center three-arm study, nicotine pharmacokinetics and influence on urge to smoke/vape were compared for tobacco cigarettes, the "initial" version of the European JUUL, and the "modified" version of the European JUUL. Participants, 15 active smokers and 17 active e-cigarette users, were instructed to consume their study product according to a pre-directed puffing protocol. Venous blood was sampled for nicotine analysis to cover the acute phase and the first 30 min after starting. Nicotine delivery and the reduction of urge to smoke/vape upon usage of both European JUUL variants were lower in comparison to tobacco cigarettes. This suggests a lower addictive potential. Modification of the pod design did not result in significant differences at the first ten puffs, as confirmed by a vaping machine experiment. Apparently, the limitations by the initially used wick material only come into effect after longer usage time.

An updated overview of e-cigarette impact on human health

The electronic cigarette (e-cigarette), for many considered as a safe alternative to conventional cigarettes, has revolutionised the tobacco industry in the last decades. In e-cigarettes, tobacco combustion is replaced by e-liquid heating, leading some manufacturers to propose that e-cigarettes have less harmful respiratory effects than tobacco consumption. Other innovative features such as the adjustment of nicotine content and the choice of pleasant flavours have won over many users. Nevertheless, the safety of e-cigarette consumption and its potential as a smoking cessation method remain controversial due to limited evidence. Moreover, it has been reported that the heating process itself can lead to the formation of new decomposition compounds of questionable toxicity. Numerous in vivo and in vitro studies have been performed to better understand the impact of these new inhalable compounds on human health. Results of toxicological analyses suggest that e-cigarettes can be safer than conventional cigarettes, although harmful effects from short-term e-cigarette use have been described. Worryingly, the potential long-term effects of e-cigarette consumption have been scarcely investigated. In this review, we take stock of the main findings in this field and their consequences for human health including coronavirus disease 2019 (COVID-19).

Electronic cigarettes for smoking cessation

BACKGROUND

Electronic cigarettes (ECs) are handheld electronic vaping devices which produce an aerosol formed by heating an e-liquid. Some people who smoke use ECs to stop or reduce smoking, but some organizations, advocacy groups and policymakers have discouraged this, citing lack of evidence of efficacy and safety. People who smoke, healthcare providers and regulators want to know if ECs can help people quit and if they are safe to use for this purpose. This is an update of a review first published in 2014.

OBJECTIVES

To examine the effectiveness, tolerability, and safety of using electronic cigarettes (ECs) to help people who smoke achieve long-term smoking abstinence.

SEARCH METHODS

We searched the Cochrane Tobacco Addiction Group's Specialized Register, the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, Embase, and PsycINFO to 1 February 2021, together with reference-checking and contact with study authors.

SELECTION CRITERIA

We included randomized controlled trials (RCTs) and randomized cross-over trials in which people who smoke were randomized to an EC or control condition. We also included uncontrolled intervention studies in which all participants received an EC intervention. To be included, studies had to report abstinence from cigarettes at six months or longer and/or data on adverse events (AEs) or other markers of safety at one week or longer.

DATA COLLECTION AND ANALYSIS

We followed standard Cochrane methods for screening and data extraction. Our primary outcome measures were abstinence from smoking after at least six months follow-up, adverse events (AEs), and serious adverse events (SAEs). Secondary outcomes included changes in carbon monoxide, blood pressure, heart rate, blood oxygen saturation, lung function, and levels of known carcinogens/toxicants. We used a fixed-effect Mantel-Haenszel model to calculate the risk ratio (RR) with a 95% confidence interval (CI) for dichotomous outcomes. For continuous outcomes, we calculated mean differences. Where appropriate, we pooled data from these studies in meta-analyses.

MAIN RESULTS

We included 56 completed studies, representing 12,804 participants, of which 29 were RCTs. Six of the 56 included studies were new to this review update. Of the included studies, we rated five (all contributing to our main comparisons) at low risk of bias overall, 41 at high risk overall (including the 25 non-randomized studies), and the remainder at unclear risk. There was moderate-certainty evidence, limited by imprecision, that quit rates were higher in people randomized to nicotine EC than in those randomized to nicotine replacement therapy (NRT) (risk ratio (RR) 1.69, 95% confidence interval (CI) 1.25 to 2.27; I2 = 0%; 3 studies, 1498 participants). In absolute terms, this might translate to an additional four successful quitters per 100 (95% CI 2 to 8). There was low-certainty evidence (limited by very serious imprecision) that the rate of occurrence of AEs was similar) (RR 0.98, 95% CI 0.80 to 1.19; I2 = 0%; 2 studies, 485 participants). SAEs occurred rarely, with no evidence that their frequency differed between nicotine EC and NRT, but very serious imprecision led to low certainty in this finding (RR 1.37, 95% CI 0.77 to 2.41: I2 = n/a; 2 studies, 727 participants). There was moderate-certainty evidence, again limited by imprecision, that quit rates were higher in people randomized to nicotine EC than to non-nicotine EC (RR 1.70, 95% CI 1.03 to 2.81; I2 = 0%; 4 studies, 1057 participants). In absolute terms, this might again lead to an additional four successful quitters per 100 (95% CI 0 to 11). These trials mainly used older EC with relatively low nicotine delivery. There was moderate-certainty evidence of no difference in the rate of AEs between these groups (RR 1.01, 95% CI 0.91 to 1.11; I2 = 0%; 3 studies, 601 participants). There was insufficient evidence to determine whether rates of SAEs differed between groups, due to very serious imprecision (RR 0.60, 95% CI 0.15 to 2.44; I2 = n/a; 4 studies, 494 participants). Compared to behavioral support only/no support, quit rates were higher for participants randomized to nicotine EC (RR 2.70, 95% CI 1.39 to 5.26; I2 = 0%; 5 studies, 2561 participants). In absolute terms this represents an increase of seven per 100 (95% CI 2 to 17). However, this finding was of very low certainty, due to issues with imprecision and risk of bias. There was no evidence that the rate of SAEs differed, but some evidence that non-serious AEs were more common in people randomized to nicotine EC (AEs: RR 1.22, 95% CI 1.12 to 1.32; I2 = 41%, low certainty; 4 studies, 765 participants; SAEs: RR 1.17, 95% CI 0.33 to 4.09; I2 = 5%; 6 studies, 1011 participants, very low certainty). Data from non-randomized studies were consistent with RCT data. The most commonly reported AEs were throat/mouth irritation, headache, cough, and nausea, which tended to dissipate with continued use. Very few studies reported data on other outcomes or comparisons and hence evidence for these is limited, with confidence intervals often encompassing clinically significant harm and benefit.

AUTHORS' CONCLUSIONS

There is moderate-certainty evidence that ECs with nicotine increase quit rates compared to ECs without nicotine and compared to NRT. Evidence comparing nicotine EC with usual care/no treatment also suggests benefit, but is less certain. More studies are needed to confirm the size of effect, particularly when using modern EC products. Confidence intervals were for the most part wide for data on AEs, SAEs and other safety markers, though evidence indicated no difference in AEs between nicotine and non-nicotine ECs. Overall incidence of SAEs was low across all study arms. We did not detect any clear evidence of harm from nicotine EC, but longest follow-up was two years and the overall number of studies was small. The evidence is limited mainly by imprecision due to the small number of RCTs, often with low event rates. Further RCTs are underway. To ensure the review continues to provide up-to-date information, this review is now a living systematic review. We run searches monthly, with the review updated when relevant new evidence becomes available. Please refer to the Cochrane Database of Systematic Reviews for the review's current status.

Public health implications of vaping in the USA: the smoking and vaping simulation model

Background

Nicotine vaping products (NVPs) are increasingly popular worldwide. They may provide public health benefits if used as a substitute for smoking, but may create public health harms if used as a gateway to smoking or to discourage smoking cessation. This paper presents the Smoking and Vaping Model (SAVM), a user-friendly model which estimates the public health implications of NVPs in the USA.

Methods

SAVM adopts a cohort approach. We derive public health implications by comparing smoking- and NVP-attributable deaths and life-years lost under a No-NVP and an NVP Scenario. The No-NVP Scenario projects current, former, and never smoking rates via smoking initiation and cessation rates, with their respective mortality rates. The NVP Scenario allows for smoking- and NVP-specific mortality rates, switching from cigarette to NVP use, separate NVP and smoking initiation rates, and separate NVP and smoking cessation rates. After validating the model against recent US survey data, we present the base model with extensive sensitivity analyses.

Results

The SAVM projects that under current patterns of US NVP use and substitution, NVP use will translate into 1.8 million premature smoking- and vaping-attributable deaths avoided and 38.9 million life-years gained between 2013 and 2060. When the NVP relative risk is set to 5%, the results are sensitive to the level of switching and smoking cessation rates and to a lesser extent smoking initiation rates. When the NVP relative risk is raised to 40%, the public health gains in terms of averted deaths and LYL are reduced by 42% in the base case, and the results become much more sensitive to variations in the base case parameters.

Discussion

Policymakers, researchers, and other public health stakeholders can apply the SAVM to estimate the potential public health impact of NVPs in their country or region using their own data sources. In developing new simulation models involving NVPs, it will be important to conduct extensive sensitivity analysis and continually update and validate with new data.

Conclusion

The SAVM indicates the potential benefits of NVP use. However, given the uncertainty surrounding model parameters, extensive sensitivity analysis becomes particularly important.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12963-021-00250-7.

Effect of an electronic nicotine delivery system with 0, 8, or 36 mg/mL liquid nicotine versus a cigarette substitute on tobacco-related toxicant exposure: a four-arm, parallel-group, randomised, controlled trial

BACKGROUND

Electronic nicotine delivery systems (ENDSs) are used by some smokers to reduce cigarette consumption, but their effectiveness is uncertain. We aimed to examine the extent to which ENDSs or a non-nicotine cigarette substitute influence tobacco-related toxicant exposure and cigarette consumption in smokers interested in smoking reduction.

METHODS

We did a four-arm, parallel-group, randomised controlled trial at two sites in the USA (Penn State University, Hershey, PA, and Virginia Commonwealth University, Richmond, VA). We enrolled adults aged 21-65 years who smoked more than nine cigarettes per day (for at least the past year), with exhaled CO of more than 9 parts per million at screening, who were not currently using an ENDS, and who were interested in reducing smoking but not quitting. Participants were randomised (site-specific with allocation concealment; 1:1:1:1) to receive either a cartomiser-based, pen-style ENDS (eGo-style) paired with 0, 8, or 36 mg/mL liquid nicotine (participants and researchers masked to concentration) or a non-ENDS cigarette-shaped plastic tube that delivered no nicotine or aerosol (cigarette substitute; unmasked) for 24 weeks. Conditions were chosen to reflect a range of nicotine delivery including none (cigarette substitute and 0 mg/mL ENDS), low (8 mg/mL), and cigarette-like (36 mg/mL), and all conditions were paired with smoking reduction instructions. The primary outcome was concentration of the tobacco-specific carcinogen metabolite 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL; urinary total) collected at randomisation and at 4, 12, and 24 weeks. Multiple imputation with and without covariate adjustment was used in addition to sensitivity analyses. This trial is registered with ClinicalTrials.gov, NCT02342795.

FINDINGS

Between July 22, 2015, and Nov 16, 2017, 684 individuals were screened and 520 (76%) were enrolled and randomised. 188 (36%) of 520 participants were lost to follow-up by week 24; attrition did not differ by study group (39 [30%] of 130 in the cigarette substitute group, 56 [43%] of 130 in the ENDS with 0 mg/mL nicotine group, 49 [38%] of 130 in the ENDS 8 mg/mL group, and 44 [34%] of 130 in the ENDS 36 mg/mL group). Urinary total NNAL at 24 weeks in the ENDS with 36 mg/mL nicotine group was 210·80 pg/mg creatinine (95% CI 163·03-274·42) compared with 346·09 pg/mg creatinine (265·00-455·32) in the cigarette substitute group (p=0·0061). No other significant differences between groups were observed for any time point for urinary total NNAL. Serious adverse event frequency was similar across groups (12 events in 12 participants [9%] in the ENDS with 36 mg/mL nicotine group, seven events in six participants [5%] in the 8 mg/mL group, 11 events in ten participants [8%] in the 0 mg/mL group, and 13 events in 13 participants [10%] in the cigarette substitute group), and all of these were deemed unrelated or unlikely to be related to study product use. There was one death between randomisation and 24 weeks (suicide; in the ENDS with 0 mg/mL nicotine group).

INTERPRETATION

Use of an ENDS with cigarette-like nicotine delivery can reduce exposure to a major pulmonary carcinogen, NNAL, even with concurrent smoking. Future ENDS trials should involve products with well characterised nicotine delivery, including those with nicotine delivery approaching that of a cigarette.

FUNDING

National Institutes of Health, US Food and Drug Administration.

Biomarkers of Toxicant Exposure and Inflammation Among Women of Reproductive Age Who Use Electronic or Conventional Cigarettes

Background: Electronic cigarettes (e-cigarettes) generally have a more favorable toxicant profile than conventional cigarettes; however, limited information exists for women of reproductive age (WRA). Our aim was to compare biomarkers of toxicant exposure, inflammation, and oxidative stress among WRA who self-report exclusive e-cigarette use, exclusive cigarette smoking, or never tobacco use (controls). Methods: Multivariable linear regression models were used to compare the geometric means of urinary biomarkers of toxicant exposure and their metabolites, serum markers of inflammation [highly sensitive C-reactive protein, soluble intercellular adhesion molecule (sICAM), interleukin 6, fibrinogen], and a measurement of oxidative stress [prostaglandin F2a-8-isoprostane (F2PG2a)] among WRA from the Population Assessment of Tobacco and Health survey. Results: E-cigarette users had higher levels of lead, tobacco-specific nitrosamines, nicotine metabolites, and some volatile organic compounds (VOCs) than controls. Except for cadmium and lead, e-cigarette users had lower levels of the analyzed urinary toxicant biomarkers compared with cigarette smokers. Cigarette smokers had higher levels of all the biomarkers of toxicant exposure than controls. There were no significant differences in the levels of markers of inflammation and oxidative stress between e-cigarette users and controls. E-cigarette users and controls had lower levels of sICAM and F2PG2a than cigarette smokers. Conclusion: WRA who use e-cigarettes had lower levels of some of the evaluated urinary biomarkers of toxicant exposure and serum biomarkers of inflammation and oxidative stress than those who smoke cigarettes, but higher lead, nicotine metabolites, and some VOCs than controls, which can increase health risks.

An Open-Label, Randomized, Controlled, Crossover Study to Assess Nicotine Pharmacokinetics and Subjective Effects of the JUUL System with Three Nicotine Concentrations Relative to Combustible Cigarettes in Adult Smokers

Introduction

This randomized, open-label, crossover clinical study evaluated nicotine pharmacokinetics (PK) and subjective effects of the JUUL System (JS; Juul Labs, Inc.) with three nicotine concentrations compared to the usual brand (UB) cigarettes in 24 adult smokers.

Methods

At five study visits, subjects used either the JS in 59 mg/mL, JS 18 mg/mL (two visits), and JS 9 mg/mL (all tobacco-flavored) or smoked their UB cigarette first during a controlled puffing sequence (CPS) and then ad libitum (5 min) use sessions. Blood samples were taken at specified timepoints for 60 min in each session. The modified Product Evaluation Scale assessed subjective effects 30-min post-use in the CPS session.

Results

Maximum plasma nicotine concentration (C_max-BL), total nicotine exposure (AUC_0-60-BL), and rate of plasma nicotine rise were significantly lower for all JS products compared to subjects' UB cigarette in CPS and ad libitum use sessions. In both use sessions these PK parameters were significantly higher for JS 59 mg/mL compared to 18 and 9 mg/mL. Subjective measures of cigarette craving relief and “Enough Nicotine” for JS 59 mg/mL did not differ significantly from UB cigarettes, but JS 18 and 9 mg/mL were rated significantly lower than JS 59 mg/mL and UB cigarettes.

Conclusions

Nicotine exposure and subjective relief were directly related to JS nicotine concentration: higher nicotine concentrations gave rise to significantly greater plasma nicotine levels and relief from craving. Heavier and more dependent smokers may require the greater nicotine delivery of JS 59 mg/mL to successfully transition away from cigarettes.

Implications

It has been suggested that electronic nicotine delivery systems (ENDS) and other alternative nicotine delivery products that more closely mimic the nicotine pharmacokinetics (PK) of cigarettes may facilitate smokers transitioning away from cigarettes. We examined nicotine PK and subjective effects of JUUL System (JS) ENDS with three nicotine concentrations (59, 18 and 9 mg/mL) compared to combustible cigarettes. Nicotine delivery from JS ENDS was nicotine concentration dependent, with higher nicotine concentrations giving rise to higher nicotine exposure. These findings suggest that heavier and more dependent smokers may require ENDS with nicotine concentrations greater than 20 mg/mL to successfully transition away from cigarettes.

Dependence and Use Characteristics of Adult JUUL Electronic Cigarette Users

JUUL is a popular electronic cigarette (e-cig) that is capable of delivering nicotine similarly to a cigarette. While known to deliver high doses of nicotine, there is little systematic evidence to show how the nicotine delivery of JUUL translates to user dependence. Purpose: The purpose of the study was to evaluate self-reported dependence of JUUL users and examine the relationship of dependence to user behaviors. Methods: Current JUUL users were recruited via Amazon Mechanical Turk to complete an online survey about their use of JUUL. Participants were asked to complete the Penn State Electronic Cigarette Dependence Index (PSECDI) and to answer questions about their use patterns and other tobacco use. Means and frequencies were used to describe the sample. A linear regression model was used to predict user dependence. Results: Participants (n = 76) were 65.4% male with a mean age of 31.9 (SD = 8.3) years. The mean PSECDI score was 7.8 (SD = 4.2) and ranged from no (15.8%) to high (14.5%) dependence. Overall predictors of a greater PSECDI score included reporting ever stealth vaping (β = 2.8, p < .01) and reporting greater use days in the past 30 (β = 3.5, p < .01). Conclusions: On average, JUUL users reported low to medium nicotine dependence on the PSECDI. JUUL user dependence may be more similar to e-cig user dependence than cigarette smoker dependence. These preliminary findings should be followed up in studies of larger samples of Juul users, collecting multiple measures of dependence, as well as biomarkers of nicotine intake (e.g. cotinine).

Association between e-cigarette use and future combustible cigarette use: Evidence from a prospective cohort of youth and young adults, 2017-2019

INTRODUCTION

A surge in popularity of e-cigarettes prompts concern given the association between e-cigarettes and future cigarette use. However, much of the evidence for this association comes from early, less efficient, and lower nicotine e-cigarettes than are available and widely used now. The goal of this study was to examine the relationship between e-cigarette use in 2018 and subsequent smoking initiation and continued e-cigarette use.

METHODS

Participants included members of a national longitudinal panel of youth and young adults aged 15-27 who, in 2017, reported never having used a nicotine containing product (n = 3360). Logistic regression analyses assessed associations between participants' self-reported ever e-cigarette use in 2018 and ever cigarette use, current cigarette use, and current e-cigarette use in 2019, after controlling for demographic and psychosocial variables.

RESULTS

Compared with those who still had never used an e-cigarette, those who reported ever e-cigarette use in 2018 had significantly higher odds of ever cigarette use (aOR = 7.29, 95% CI [4.10, 12.97]), current cigarette use (aOR = 8.26, 95% CI [3.17, 21.53]), and current e-cigarette use (aOR = 9.70, 95% CI [6.41, 14.69]) one year later in 2019.

CONCLUSIONS

These findings show that the pod mod style, high nicotine containing e-cigarettes subject young users to the same risks of transitioning to combustible cigarettes as their earlier, less efficient predecessors. Strong regulation of all nicotine products, including e-cigarettes, is needed to prevent the trajectory of e-cigarette to cigarette use among youth and young adults.

Response to Flavored Cartridge/Pod-Based Product Ban among Adult JUUL Users: "You Get Nicotine However You Can Get It"

In order to curb increasing youth electronic cigarette (e-cig) use, the United States Food and Drug Administration (FDA) banned the sale of flavored cartridge/pod-based products in February 2020. This mixed-methods study aimed to evaluate the impact of the FDA ban on adult JUUL users. The samples of current adult JUUL users were surveyed via Amazon Mechanical Turk at three time-points n = 76 (Sample 1); n = 128 (Sample 2); n = 86 (Sample 3) before and after the FDA flavored/pod ban. The participants were asked to report the JUUL flavored pod used most often and answer questions on purchasing generic pods or refilling (Quantitative). JUUL users were then interviewed in order to explore their perceptions and behaviors related to the FDA ban of flavored cartridge/pod-based products (Qualitative; n = 16). Quantitative data analysis evaluated the differences in variables by time-point. Qualitative data were coded into themes while using the constant comparative method. We found a significant decrease in the use of mint pods (43.4%, 22.7%, 16.3%) (p < 0.01), while there was a significant increase in the use of menthol pods (6.6%, 26.6%, 37.2%) (p < 0.01). Themes that emerged from the qualitative data included switching from mint to menthol pods, refilling pods, and switching to other products that are available in the desired flavors, such as generic pods or disposable e-cigs. Future research is needed in order to evaluate the impact of these behaviors on public health.

Nicotine pharmacokinetics of electronic cigarettes: A pooled data analysis from the literature

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Evaluating the pharmacokinetics of nicotine absorption from electronic cigarettes.

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Nicotine absorption into the blood is influenced by several factors.

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These include e-liquid composition, user behavior and device characteristics.

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Any regulation of nicotine levels in e-liquids should reflect this heterogeneity.

Several regulatory initiatives around the world restrict the amount of nicotine permitted in electronic cigarette liquids in an attempt to reproduce the nicotine delivery of combusted tobacco products, such as cigarettes, and or reduce the risk of consumers absorbing too much nicotine into their body at one time. Such an approach, however, assumes that (i) there is a strong correlation between the levels of nicotine in electronic cigarette liquids and nicotine intake into the body and (ii) that this correlation holds true across the various different types of electronic cigarette devices currently available on the market. In order to test these hypotheses, this study examines the available scientific literature on nicotine intake from electronic cigarettes, as measured by levels in the blood. Analysis of the published data reveals that nicotine absorption into the body is influenced by a combination of many factors, including electronic cigarette liquid composition, user behavior and device characteristics. Notably, it was observed that open-tank (refillable) electronic cigarettes, which often enable users to vary device power, can deliver high nicotine levels to consumers, sometimes at greater doses than a conventional tobacco cigarette, even at the lower nicotine liquid concentrations typically available. For electronic cigarettes to be viable alternative choices to smoking, they should provide consumers with an equally satisfying experience, including in terms of nicotine absorption into the body. Therefore, any regulation seeking to restrict the amount of nicotine in electronic cigarette liquids should take all the factors influencing nicotine intake into account.

Critical research gaps in electronic cigarette devices and nicotine aerosols

Electronic cigarettes (e-cigs) are devices that aerosolize nicotine-containing liquids for delivery as an inhaled vapor. E-cigs are currently marketed as smoking cessation devices, though the emergence and rapid adoption of these devices in recent years has sparked a great deal of concern over their safety. Given the plethora of devices and nicotine solutions available on the market and the lack of regulation and quality control, it is imperative that these devices and nicotine formulations are studied to assess critical operating parameters, the pharmacokinetic profiles of the inhaled nicotine, and the toxicity profiles of the e-cig aerosols. This review aims to deliver an overview of current research regarding electronic cigarette devices, nicotine-containing liquid formulations, pharmacokinetics of nicotine, and toxicology studies in order to highlight areas lacking in research or requiring greater standardization and regulation.

A comparison of product dependence among cigarette only, ENDS only, and dual users: Findings from Wave 3 (2015-2016) of the PATH study

INTRODUCTION

Little is known about differences in tobacco product dependence among people who use two tobacco products versus one. Self-reported product dependence among individuals using cigarettes only, electronic nicotine delivery systems (ENDS) only, and both cigarettes and ENDS (dual users) was compared.

METHOD

PATH Wave 3 data were collected between 2015 and 2016. We used 11 Wisconsin Inventory of Smoking Dependence Motives items to assess cigarette and ENDS dependence, averaged to generate Cigarette Dependence (CD) and ENDS Dependence (ED) scores. Linear regression models were used to assess the association between tobacco use groups and the two dependence scores.

RESULTS

Our analytic sample included 5538 (91.5 %) cigarette only, 399 (6.7 %) ENDS only, and 108 (1.8 %) dual users. There was no difference in CD between cigarette only and dual users. ENDS only users' ED (2.11, SE = 0.05) was higher than dual users' ED (1.67, SE = 0.04) (p < 0.05). Dual users' mean ED (1.70, SE = 0.09) was significantly lower than their CD (3.03, SE = 0.11) (p < 0.001), and ENDS only users' ED (2.34, SE = 0.05) was significantly lower than cigarette only users' CD (2.94, SE = 0.02) (p < 0.001).

CONCLUSION

While there was no difference in CD between dual and cigarette only users, dual users' ED was lower than that for ENDS only users. ENDS appeared to produce less dependence than cigarettes among dual users. Given the high nicotine concentration ENDS products that entered the market after PATH Wave 3 data were collected, future research should examine ED among ENDS only and dual users.

Variable Voltage, Tank-Style ENDS Do Not Always Deliver Nicotine

Objective

This study's objective was to characterize the nicotine delivery profile of a variable voltage, tank-style electronic nicotine delivery system (ENDS).

Methods

Ten cigarette smokers (8 men, 2 women) completed this within-subject study assessing effects of 2 device power settings (15 W, 45 W) and 3 liquid nicotine concentrations (0, 3, and 6 mg/ml) using a tank-style ENDS. Participants completed one directed (10 puffs) and one ad libitum use period for each condition, with blood sampled throughout.

Results

Plasma nicotine concentration did not increase significantly at 15 W regardless of liquid nicotine concentration. At 45 W, mean plasma nicotine increased (not significantly compared to 0 mg/ml) from 2.24 ng/ml (SD=0.2) at baseline to 3.4 ng/ml (SD=0.6) in the 3 mg/ml condition. In the 6 mg/ml, 45 W condition, mean plasma nicotine increased significantly (compared to 0 mg/ml) from 2.0 ng/ml (SD=0) at baseline to 5.96 ng/ml (SD=1.3) after 10 puffs. In general, puff duration and volume decreased as device power and nicotine concentration increased.

Conclusions

Despite using a variable wattage, tank-style device, nicotine delivery was minimal. These results, when combined with results from other studies using tank-style devices, highlight ENDS performance heterogeneity. Regulation may play a role in standardizing ENDS nicotine delivery.