Self-titration by experienced e-cigarette users: blood nicotine delivery and subjective effects

Drug discrimination learning: Interoceptive stimulus control of behavior and its implications for regulated and dysregulated drug intake

Drug discrimination research has generated rich evidence for the capacity of interoceptive drug stimuli to control behavior by serving as discriminative cues. Owing to its neuropharmacological specificity, drug discrimination learning has been widely used to characterize the stimulus effects and neuropharmacological underpinning of drugs. Apart from such utility, discriminative drug stimuli may help regulate drug use by disambiguating conditioned associations and post-intake outcomes. First, this review summarizes the evidence supporting interoceptive regulation of drug intake from the literature of exteroceptive discriminative control of drug-related behavior, effects of drug priming, and self-titration of drug intake. Second, an overview of interoceptive control of reward-seeking and the animal model of discriminated goal-tracking is provided to illustrate interoceptive stimulus control of the initiation and patterning of drug intake. Third, we highlight the importance of interoceptive control of aversion-avoidance in the termination of drug-use episodes and describe the animal model of discriminated taste avoidance that supports such a position. In bridging these discriminative functions of drug stimuli, we propose that interoceptive drug stimuli help regulate intake by disambiguating whether intake will be rewarding, nonrewarding, or aversive. The reflection and discussion on current theoretical formulations of interoceptive control of drug intake may further scientific advances to improve animal models to study the mechanisms by which interoceptive stimuli regulate drug intake, as well as how alterations of interoceptive processes may contribute to the transition to dysregulated drug use.

Stimulus mediation, specificity and impact of menthol in rats trained to discriminate puffs of nicotine e-cigarette aerosol from nicotine-free aerosol

RATIONALE

It is unclear if e-cigarettes have reduced abuse liability relative to traditional cigarettes, especially when considering advanced devices which deliver nicotine more efficiently. Translatable and predictive animal models are needed to addresses this question.

OBJECTIVES

Our goal was to explore the subjective stimulus effects of e-cigarettes by training rats to discriminate puffs of nicotine aerosol from vehicle aerosol using an aerosol delivery system designed to model e-cigarette use patterns in humans.

METHODS

Rats were trained to discriminate between ten, 10 s puffs of aerosol generated from 3 mg/ml nicotine e-liquid and nicotine-free e-liquid using a food-reinforced operant procedure. Following acquisition, tests were conducted to determine the specificity of the nicotine aerosol stimulus as well as the impact to the stimulus effects of nicotine resulting from the addition of menthol to e-liquid.

RESULTS

Rats learned the nicotine aerosol puff vs vehicle puff discrimination in a mean of 25 training sessions. Injected nicotine fully substituted for the stimulus effects of nicotine aerosol. The stimulus effects of nicotine aerosol were blocked by the nicotinic receptor antagonist mecamylamine. The nicotinic receptor partial agonist, varenicline as well as the stimulant d-amphetamine substituted more robustly for nicotine aerosol puffs than did the NMDA antagonist, ketamine. Menthol enhanced the stimulus effects of nicotine aerosol without altering nicotine blood plasma levels.

CONCLUSIONS

Nicotine aerosol puffs can function as a training stimulus in rats. The stimulus effects were CNS-mediated and receptor specific. Menthol appears to enhance the stimulus effects of nicotine aerosol through a pharmacodynamic rather than pharmacokinetic mechanism.

Partial Nicotine Reduction and E-Cigarette Users' Puffing Behaviors Among Adults Aged 21 to 35 Years: A Randomized Crossover Clinical Trial

Importance

The advent of salt-based, high-nicotine electronic nicotine delivery systems [e-cigarettes] has contributed to their epidemic use among young people in the US, necessitating the need for policies to address the addictiveness of these products.

Objective

To evaluate the effect of partial nicotine reduction on new-generation e-cigarette users' puffing behaviors.

Design, Setting, and Participants

This randomized crossover clinical trial was conducted at the Clinical Research Lab for Tobacco Smoking at Florida International University in Miami between April 15, 2022, and October 17, 2023. Using a volunteering sampling method by distributing flyers and advertisements, current e-cigarette users (who preferred 5% nicotine concentration), aged 21 to 35 years, were included.

Intervention

In a crossover design, participants completed 2 sessions of the same product (JUUL or NJOY) that differed by nicotine concentration (3% [JUUL] or 2.4% [NJOY] and 5% [JUUL or NJOY]) in random order. In each session, participants vaped up to 60 minutes ad libitum, preceded by 12 hours of nicotine abstinence.

Main Outcomes and Measures

The primary outcomes were puffing topography parameters (eg, total session time, puffing time, total puffing number, interpuff interval, total inhaled volume, average puff volume, duration, and flow rate) measured during each session and plasma nicotine measured before and after each session.

Results

Among 735 participants who were approached for eligibility, 675 were excluded, and 10 did not complete session 2. Of the 50 remaining current e-cigarette users (mean [SD] age, 23 [3] years; 56% men), 23 (46%) were low nicotine dependent. The median topography parameters were significantly higher during the e-cigarette use sessions with 3% or 2.4% nicotine concentration compared with 5% nicotine concentration for 3 outcomes: puffing time (1.3 minutes [IQR, 0.3-9.4 minutes] vs 1.2 minutes [IQR, 0.2-5.6 minutes]; P = .02), puff duration (2.6 seconds [IQR, 0.8-6.9 seconds] vs 2.4 seconds [IQR, 0.4-6.6 seconds]; P = .02), and total inhaled volume (1990.0 mL [IQR, 279.0-24 400.0 mL] vs 1490.0 mL [IQR, 148.0-14 300.0 mL]; P = .05). The median plasma nicotine boost observed in the 5% nicotine concentration condition (0.0060 mg/L [IQR, 0.0001-0.0249 mg/L]) was significantly higher than that in the 3% or 2.4% session (0.0043 mg/L [IQR, 0.0008-0.0225 mg/L]) (P = .001). Additionally, deeper puffing (increased average puff duration and average puff volume) was observed in participants with higher nicotine dependence (1.42 seconds [95% CI, 1.12-1.80 seconds]; P = .03) and male users (1.38 mL [95% CI, 1.09-1.75 mL]; P = .04) in response to nicotine reduction.

Conclusions and Relevance

This randomized crossover clinical trial provides direct evidence that partial nicotine reduction in salt-based e-cigarettes was associated with acute compensatory puffing and the potential for increased exposure to toxicants. However, given the reduced nicotine delivery associated with nicotine reduction, the acute compensatory response observed in this study may not preclude a population benefit due to the marketing of less addictive products. These results suggest that at least for current e-cigarette users, partial nicotine reduction can lead to enhanced exposure to some toxicants in the short term.

Trial Registration

ClinicalTrials.gov Identifier: NCT05205382.

Nicotine flux and pharmacokinetics-based considerations for early assessment of nicotine delivery systems

In the past few years, technological advancements enabled the development of novel electronic nicotine delivery systems (ENDS). Several empirical measures such as "nicotine flux" are being proposed to evaluate the abuse liability potential of these products. We explored the applicability of nicotine flux for clinical nicotine pharmacokinetics (PK) and 52-week quit success from cigarettes for a wide range of existing nicotine delivery systems. We found that the differences in nicotine flux for various nicotine delivery systems are not related to changes in PK, as nicotine flux does not capture key physiological properties such as nicotine absorption rate. Further, the 52-week quit success and abuse liability potential of nicotine nasal sprays (high nicotine flux product), and nicotine inhalers (nicotine flux similar to ENDS) are low, suggesting that nicotine flux is a poor metric for the assessment of nicotine delivery systems. PK indices are more dependable for characterizing nicotine delivery systems, and a nicotine plasmaC max T max > 1 could improve 52-week quit success from cigarettes. However, a single metric may be inadequate to fully assess the abuse liability potential of nicotine delivery systems and needs to be further studied. A combination of in vitro and in silico approaches could potentially address the factors influencing the inhaled aerosol dosimetry and resulting PK of nicotine to provide early insights for ENDS assessments. Further research is required to understand nicotine dosimetry and PK for ad libitum product use, and abuse liability indicators of nicotine delivery systems. This commentary is intended to (1) highlight the need to think beyond a single empirical metric such as nicotine flux, (2) suggest potential PK-based metrics, (3) suggest the use of in vitro and in silico tools to obtain early insights into inhaled aerosol dosimetry for ENDS, and (4) emphasize the importance of considering comprehensive clinical pharmacology outcomes to evaluate nicotine delivery systems.

Effects of liquid nicotine concentration and flavour on the acceptability of electronic nicotine delivery systems (ENDS) among people who smoke participating in a randomised controlled trial to reduce cigarette consumption

BACKGROUND

Research is needed to understand the acceptability of electronic nicotine delivery systems (ENDS) as a smoking reduction aid. This study examines the acceptability of ENDS by liquid nicotine concentration and flavour among people who smoke using ENDS to reduce their smoking.

METHODS

People who smoke cigarettes but were naïve to ENDS participated in a double-blind randomised controlled trial to reduce conventional cigarette smoking. Participants were randomised to either a control cigarette substitute (CS) or one of three ENDS groups; 0 mg/mL, 8 mg/mL or 36 mg/mL nicotine concentration. ENDS flavour was chosen by the participant (tobacco or menthol). Participants reported their CS, ENDS and cigarettes per day (CPD) from the past 7 days at 1-month, 3-month and 6-month follow-up visits. Participants also reported side effects and measures of satisfaction, psychological reward, aversion and craving relief. Outcome variables were modelled using linear mixed effects by the following groups: liquid nicotine concentration, flavour and a flavour-nicotine concentration interaction.

RESULTS

Participants (n=520) were 41.2% male, 67.3% white, had a mean age of 46.2 years and smoked a mean of 18.6 CPD (SD=7.74) at baseline. All flavour and concentration groups decreased CPD from baseline to all follow-up visits with the 36 mg/mL experiencing the greatest reduction, compared with the 0 mg/mL and 8 mg/mL groups. All groups except the 36 mg/mL group decreased their product use over time. The use of menthol flavour was associated with fewer side effects at 3 months (p=0.02) and lesser aversion at 1 month (p=0.03) compared with tobacco-flavoured ENDS. The 36 mg/mL group experienced the greatest craving relief and greatest aversion compared with other groups.

CONCLUSIONS

Both nicotine concentration and flavour appear to have independent, as well as interactive, effects that influence ENDS acceptability among people who use cigarettes.

Selecting an e-cigarette for use in smoking cessation interventions and healthcare services: findings from patient and public consultation for the COSTED trial

OBJECTIVES

The Cessation of Smoking Trial in the Emergency Department (COSTED) trial aims to ascertain whether brief advice, the provision of an e-cigarette starter kit and referral to stop smoking services (SSS), increases smoking cessation in people attending the emergency department. Patient and public involvement (PPI) and scoping work were undertaken to select an appropriate e-cigarette for the trial.

DESIGN AND SETTING

PPI consultation and feasibility scoping about potential devices with a professional and lay panel, all based in England. Consultation was via email, telephone or video interview. This work took place between April and July 2021, prior to recruitment commencing for the COSTED trial.

PARTICIPANTS

A professional panel (n=7) including representatives from academia, SSS and the independent vaping industry, and a PPI lay panel (n=3) who smoke or vape.

RESULTS

The professional panel recommended a shortlist of devices which were tested by the PPI lay panel. Key criteria for selecting an appropriate e-cigarette for smoking cessation intervention include satisfaction, usability, affordability and availability. Simplicity of use was highlighted by the PPI lay panel, who found refillable devices complex, and availability of consumables was highlighted as more important than price by both panels. The pod device selected for inclusion was rated highly for satisfaction and usability and had mid-price range and consumables which were widely available.

CONCLUSIONS

To select the most appropriate device for the COSTED trial, each criterion required assessment to ensure the best fit to the intervention context and needs of the target population. There is a need for guidance to help enable decision-making about choice of vape products, tailored to service users' needs. We propose a bespoke checklist template, based on our findings, to assist with this process. This has applicability to the recent government announcement of a 'Swap to Stop' programme, offering a vaping starter kit to smokers across England, allowing services flexibility to shape their own programmes and models of delivery.

TRIAL REGISTRATION NUMBER

Clinical trial number NCT04854616; pre-results.

An 8-year longitudinal study of long-term, continuous users of electronic cigarettes

BACKGROUND AND AIMS

E-cigarettes have been available for over 15 years, but relatively little is known about long-term users. Our aim was to describe change over time in behaviours, attitudes and dependence in long-term users.

DESIGN AND PARTICIPANTS

A longitudinal study of 375 e-cigarette users enrolled on the Internet in 2012-2016 and surveyed again in 2021 (8 years later on average), who continuously used e-cigarettes in the interval.

FINDINGS

Fewer people in 2021 (11 %) than at baseline (33 %) had smoked tobacco in the past 31 days. Participants switched from second-generation models at baseline (e.g. Ego) to box mods in 2021 (e.g. iStick), they used larger refill bottles, they used home-made e-liquids twice as often, they used tobacco flavours less often and the nicotine concentration in e-liquids decreased from 12 to 6 mg/mL. There was no change over time in the time to the first e-cigarette puff of the day, but an e-cigarette dependence score of 0-100 decreased from 75 to 60, the frequency and strength of urges to vape decreased (from 31 % to 18 % of "strong" urges) and the proportion of people who said they would be likely to succeed if they tried to stop vaping increased. Compared to baseline, fewer people in 2021 reported vaping to cope with cravings or other smoking cessation symptoms, and fewer people reported vaping to quit smoking, to avoid relapse into smoking, or to reduce their tobacco consumption (p < 0.001 for all differences).

CONCLUSIONS

In long-term, continuous users, over a period of 8 years, substantial changes were observed in the models of e-cigarettes used, in the flavours and strength of e-liquids, and in the reasons for vaping. Their level of nicotine dependence tended to decrease over time. These users were satisfied with e-cigarettes and vaped mostly because they felt that vaping was less dangerous than smoking, and for enjoyment.

Symptoms of nicotine dependence by e-cigarette and cigarette use behavior and brand: A population-based, nationally representative cross-sectional study

BACKGROUND

Many modern e-cigarette brands contain equivalent or higher nicotine levels than traditional cigarettes.

OBJECTIVE

To examine differences in four nicotine dependence indicators (i.e., use within 30minutes of waking, cravings, needing to use, and frequent use) among adolescents (aged 12-17 years) with past 30-day (P30D) exclusive use of e-cigarettes, cigarettes, or dual use of both.

METHODS

Data were from Wave 5 (2018-2019) of the Population Assessment of Tobacco and Health (PATH) study (n=1060; N=2053,659). Multivariable logistic regression was performed to determine differences in indicators by P30D e-cigarette and cigarette use behavior (exclusive vs. dual use) and brand (e-cigarette use: JUUL vs. non-JUUL vs. Unknown).

RESULTS

The odds of frequent use among adolescents with JUUL (AOR: 2.11; 95% CI=1.02-4.37) and non-JUUL (AOR: 2.12; 95% CI=0.95-4.77) use were similar and paralleled that for dual use (AOR: 3.50; 95% CI=1.46-8.43) but were stronger (JUUL only) than exclusive cigarette use. The odds of using within 30minutes of waking for adolescents with JUUL (AOR: 2.23; 95% CI=0.80-6.25) and non-JUUL (AOR:1.42; 95% CI=0.47-4.32) use were similar and paralleled that for both dual (AOR=3.00; 95% CI=1.01-8.88) and exclusive cigarette use. For adolescents who used unknown brands, the odds of all indicators paralleled exclusive cigarette use but were lower than JUUL, non-JUUL, and dual use.

CONCLUSION

Compared to exclusive cigarette use, symptoms of nicotine dependence are similar for adolescents with exclusive e-cigarette use, irrespective of brand. Symptoms of nicotine dependence for JUUL and non-JUUL use parallel dual use. Tobacco regulation should consider these findings when assessing the abuse liability of e-cigarettes.

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.

Influence of nicotine form and nicotine flux on puffing behavior and mouth-level exposure to nicotine from electronic nicotine delivery systems

BACKGROUND

Nicotine form (freebase/protonated) and nicotine flux (rate at which nicotine is emitted) are two factors that can affect the dose of nicotine inhaled by individuals using electronic nicotine delivery systems (ENDS) because they can influence puffing behavior. The nicotine dose for each puff also is directly proportional to nicotine flux (i.e., dose/puff=nicotine flux*puff duration). This study examines the effect of nicotine form and flux on puffing parameters and mouth-level nicotine exposure.

METHODS

Thirty-two dual ENDS and combustible cigarette participants completed five visits that differed by nicotine form (freebase or protonated) and nicotine flux (14 or 35µg/sec); a zero-nicotine condition was a negative control. Participants used a Subox Mini C ENDS, powered at 20W, during a 10-puff directed bout (B1) followed by a one-hour ad libitum bout (B2). Puffing parameters and mouth-level nicotine exposure were assessed using the American University of Beirut REALTIME instrument.

RESULTS

Relative to protonated nicotine, freebase nicotine was associated with lower total puff duration (puff duration*number of puffs), lower flow rate in B1, lower liquid consumption, and lower mouth-level nicotine exposure. Increasing nicotine flux from 14 to 35µg/sec was associated with lower total puff duration in both bouts, as well as lower liquid consumption. Increasing nicotine flux was associated with higher mouth-level nicotine exposure in B1 only.

CONCLUSION

ENDS with protonated nicotine may enhance nicotine exposure by promoting longer puffing and thus greater dose delivered. This work highlights the importance of accounting for interactions between nicotine form and flux when considering nicotine regulation for ENDS.

Characterization of e-cigarette users according to device type, use behaviors, and self-reported health outcomes: Findings from the EMIT study

INTRODUCTION

Electronic cigarettes (e-cigarettes) rapidly evolved from large modifiable (MOD) devices, to small and affordable 'POD' devices. Detailed information on user demographics and preferences according to device type, which can inform potential chemical exposure and policy recommendations, is currently limited. The goal of this study is to describe user demographics, use behaviors and preferences, as well as self-reported health outcomes according to the e-cigarette device type used.

METHODS

From April 2019 to March 2020, 91 participants from Maryland (18 MOD users, 26 POD users, 16 dual users (use of both combustible and e-cigarettes), and 31 non-users (never e-cigarette users and never smokers or >6 months former use) were recruited. A comprehensive questionnaire collected sociodemographic characteristics, e-cigarette/tobacco use behaviors, self-reported health outcomes, device characteristics and preferences. Chi-squared tests for categorical variables, ANOVA for continuous variables, qualitative thematic analysis, linear and logistic regressions were used to assess relationships between variables and groups.

RESULTS

POD users were younger (average 22.5 years) than MOD users (30.8 years) or dual users (34.3 years) (p<0.001). MOD users reported more puffs per day (mean ± SD: 373 ± 125 puffs) compared to POD users (123.0 ± 172.5). E-cigarette users who were former smokers used 1.16 mg/mL lower nicotine concentrations compared to lifetime exclusive e-cigarette users (p=0.03) in linear models. Exclusive POD users self-reported more coughing than exclusive MOD or dual users (p=0.02). E-cigarette users reported more shortness of breath, headaches, and fatigue from their e-cigarette use compared to non-users.

CONCLUSIONS

We found significant differences between user demographics, e-cigarette preferences, device characteristics, and use behaviors by user group. This information can help explain exposure to chemicals from e-cigarettes, including compounds with known toxic effects (e.g. metals, formaldehyde), and help inform the design of prevention and intervention strategies and policy decisions.

Using a Novel Connected Device for the Collection of Puffing Topography Data for the Vuse Solo Electronic Nicotine Delivery System in a Real-World Setting: Prospective Ambulatory Clinical Study

BACKGROUND

Over the last decade, the use of electronic nicotine delivery systems (ENDSs) has risen, whereas studies that describe how consumers use these products have been limited. Most studies related to ENDS use have involved study designs focused on use in a central location environment or attempted to measure use outcomes through subjective self-reported end points. The development of accurate and reliable tools to collect data in a naturalistic real-world environment is necessary to capture the complexities of ENDS use. Using connected devices in a real-world setting provides a convenient and objective approach to collecting behavioral outcomes with ENDS.

OBJECTIVE

The Product Use and Behavior instrument was developed and used to capture the use of the Vuse Solo ENDS in an ambulatory setting to best replicate real-world use behavior. This study aims to determine overall mean values for topography outcomes while also providing a definition for an ENDS use session.

METHODS

A prospective ambulatory clinical study was performed with the Product Use and Behavior instrument. Participants (n=75) were aged between 21 and 60 years, considered in good health, and were required to be established regular users of ENDSs. To better understand use behavior within the population, the sample was sorted into percentiles with bins based on daily puff counts. To frame these data in the relevant context, they were binned into low-, moderate-, and high-use categories (10th to 40th, 40th to 70th, and 70th to 100th percentiles, respectively), with the low-use group representing the nonintense category, the high-use group representing the intense category, and the moderate-use group being reflective of the average consumer.

RESULTS

Participants with higher daily use took substantially more puffs per use session (6.71 vs 4.40) and puffed more frequently (interpuff interval: 32.78 s vs 61.66 s) than participants in the low-use group. Puff duration remained consistent across the low-, moderate‑, and high-use groups (2.10 s, 2.18 s, and 2.19 s, respectively). The moderate-use group had significantly shorter session lengths (P<.001) than the high- and low-use groups, which did not differ significantly from each other (P=.16).

CONCLUSIONS

Using connected devices allows for a convenient and robust approach to the collection of behavioral outcomes related to product use in an ambulatory setting. By using the variables captured with these tools, it becomes possible to move away from predefined periods of use to better understand topography outcomes and define use sessions. The data presented here offer a possible method to define these sessions. These data also begin to frame international standards used for the analytical assessments of ENDSs in the correct context and begin to shed light on the differences between standardized testing regimens and actual use behavior.

TRIAL REGISTRATION

Clinicaltrials.gov NCT04226404; https://clinicaltrials.gov/study/NCT04226404.

Examination of the impact of myblu electronic nicotine delivery system e-liquid nicotine strength on self-reported measures of dependence

BACKGROUND

Greater nicotine delivery is associated with higher nicotine concentrations in electronic nicotine delivery system (ENDS) liquids. However, there is a current debate as to whether this leads to increased dependence and mitigates ENDS public health potential.

METHODS

Self-reported dependence among users of myblu ENDS containing different nicotine concentrations was examined with data from a multiwave cross-sectional survey of US young adults and adults. Questions examined responses related to dependence measures and participants' most often used myblu ENDS nicotine concentration (low: 0%, 1% and 1.2%; medium: 2%, 2.4% and 2.5%; or high: 3.6% and 4%).

RESULTS

A global general linear model using nicotine concentration, age and days myblu that was used in the past 30 revealed a significant difference in PROMIS scores among nicotine concentration groups (F = 4.07, p = 0.02). However, pairwise comparisons to examine which specific groups differed significantly from others showed no significant differences. Logistic regression demonstrated that strong past 30-day cravings to use myblu among participants using high or medium nicotine concentrations were not significantly different from those using a low concentration (ORs 0.66 [0.42, 1.03], p = 0.07 and 0.95 [0.49, 1.82], p = 0.98, respectively). Time to daily first use for high or medium nicotine concentration users was not significantly different from those using a low concentration (ORs 0.89 [0.70, 1.14], p = 0.35 and 0.84 [0.57, 1.25], p = 0.40, respectively).

CONCLUSIONS

Use of myblu ENDS with different nicotine concentrations is not associated with differing levels of dependence. Our findings contradict the notion that high ENDS e-liquid nicotine levels generate increased dependence.

Part two: an unblinded, parallel, randomized study to assess nicotine pharmacokinetics of four Vuse Solo ENDS flavors in smokers

We report the findings from a randomized, parallel study designed to evaluate nicotine pharmacokinetics (PK) following 10 min of ad libitum use of electronic nicotine delivery system (ENDS) in four flavor variants. Subjects were randomized an investigational product (IP) and blood samples were collected for PK assessments during a test session. Primary endpoints were baseline-adjusted values of maximum plasma nicotine concentration (C_max) and area under the nicotine concentration-vs-time curve up to 60 min (AUC_nic0-60). Baseline-adjusted mean C_max ranged from 6.53 to 8.21 ng/mL, and mean AUC_nic0-60 ranged from 206.87 to 263.52 ng min/mL for all ENDS IPs. Results of geometric mean C_max and AUC_nic0-60 values were within 95% confidence intervals (CI) among the ENDS IP flavor variants tested.

Comparing the Effects of the EU- Versus the US-JUUL Pod in a Sample of UK Smokers: Nicotine Absorption, Satisfaction, and Other Nicotine-Related Subjective Effects

INTRODUCTION

Pod Vaping Devices (PVD) such as JUUL have become extremely popular in the United States although their uptake and use in the United Kingdom remain lower. A key difference between the United States and the United Kingdom is the nicotine strength legally permitted, typically 59 mg/mL in the United States but capped at 20 mg/mL in the United Kingdom and European Union. This may limit the ability of EU vaping devices to deliver satisfactory nicotine levels. The primary aim was to compare the EU- (18 mg/mL nicotine strength) with the U.S.-JUUL (59 mg/mL) on daily smokers' subjective experiences, craving relief, and blood nicotine levels.

AIMS AND METHODS

Double-blind, counterbalanced within-participants design with two conditions: 18 mg/mL versus 59 mg/mL. On two separate occasions, UK smokers (N =19, 10 males, 9 females) vaped ad libitum for 60 mins and provided blood samples at baseline 5, 15, 30, and 60 min. Subjective effects (incl. satisfaction) were measured at 10 and 60 min and, craving and withdrawal symptoms (WS) at baseline, 10 and 60 min.

RESULTS

Satisfaction did not differ between conditions. There was a significant interaction between Time and Nicotine concentration for Nicotine Hit (p = .045). Mean self-report of Nicotine Hit increased under the use of the 59 mg/mL from 10 to 60 min and decreased under the 18 mg/mL. Participants reported higher Throat Hits following use of the 59 mg/mL (p = .017). There were no differences in other subjective effects including craving, WS relief (ps > .05). Liquid consumption was doubled under the 18 versus the 59 mg/mL (p = .001) and nicotine boost was significantly higher in the 59 mg/mL at all time-points (p ≤ .001).

CONCLUSIONS

The results did not support our hypotheses that satisfaction, craving, and withdrawal reduction would be higher with the 59 mg/mL JUUL. This could be because of the doubling of liquid consumption in the 18 mg/mL. Whether satisfaction and craving relief persist over the longer-term outside of the lab remains to be determined.

IMPLICATIONS

In a 60-min ad-lib vaping session, the EU-JUUL was found to produce comparable satisfaction, craving- and withdrawal relief as the U.S.-JUUL in this sample of UK smokers. These findings could suggest that the higher nicotine concentrations available in PVDs in the United States are not necessary for providing satisfaction and improving craving and WS. However, this was at the expense of a considerable increase in liquid consumption indicative of compensatory puffing.

E-cigarette exposure augments murine abdominal aortic aneurysm development: role of Chil1

AIMS

Abdominal aortic aneurysm (AAA) is a common cardiovascular disease with a strong correlation to smoking, although underlying mechanisms have been minimally explored. Electronic cigarettes (e-cigs) have gained recent broad popularity and can deliver nicotine at comparable levels to tobacco cigarettes, but effects on AAA development are unknown.

METHODS AND RESULTS

We evaluated the impact of daily e-cig vaping with nicotine on AAA using two complementary murine models and found that exposure enhanced aneurysm development in both models and genders. E-cigs induced changes in key mediators of AAA development including cytokine chitinase-3-like protein 1 (CHI3L1/Chil1) and its targeting microRNA-24 (miR-24). We show that nicotine triggers inflammatory signalling and reactive oxygen species while modulating miR-24 and CHI3L1/Chil1 in vitro and that Chil1 is crucial to e-cig-augmented aneurysm formation using a knockout model.

CONCLUSIONS

In conclusion our work shows increased aneurysm formation along with augmented vascular inflammation in response to e-cig exposure with nicotine. Further, we identify Chil1 as a key mediator in this context. Our data raise concerns regarding the potentially harmful long-term effects of e-cig nicotine vaping.

Comparing POD and MOD ENDS Users' Product Characteristics, Use Behaviors, and Nicotine Exposure

INTRODUCTION

POD electronic nicotine delivery systems (ENDS), often containing high concentrations of nicotine salts, have replaced MODs (ie, open/modifiable devices) as the most popular devices. The purpose of this study was to compare device/liquid characteristics, use behavior, and nicotine exposure between POD and MOD users.

METHODS

Data from the initial visit of a prospective observational study of exclusive ENDS users compared MOD (n = 48) and POD (n = 37) users. Participants completed questionnaires on demographic characteristics, patterns of ENDS use, and ENDS features. A urine sample was collected to test for cotinine and an ENDS liquid sample was collected to test for nicotine and salts. Puff topography was captured during an ad libitum bout at the end of the session.

RESULTS

MOD and POD users did not differ on demographic characteristics. MOD users reported purchasing more liquid in the past month than POD users (180.4 ± 28.0 vs. 50.9 ± 9.0 ml, p < .001). Differences in characteristics of devices used by MOD and POD users included flavor type (p = .029), nicotine concentration (liquids used by MOD users contained less nicotine than those used by POD users: 8.9 ± 2.0 vs. 41.6 ± 3.2 mg/ml, p < .001), and presence of the nicotine salt (fewer MOD liquids had salts present than POD liquids: 11.9% vs. 77.4%, p < .001). User groups did not differ on urinary cotinine levels or puff topography (ps > .05).

CONCLUSIONS

Despite different characteristics of MOD and POD ENDS, users of those products are exposed to similar amounts of nicotine, likely due to using more liquid among MOD users.

IMPLICATIONS

This study directly compares ENDS product characteristics, user behavior, and nicotine exposure between MOD and POD ENDS users. Although POD products contained higher nicotine concentrations compared to MOD products, users of PODs reported consuming less liquid than MOD users. Ultimately, MOD and POD users were exposed to similar levels of nicotine, suggesting users behaviorally compensate for differences in product characteristics.

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.

Exposure-response analysis of the association of maternal smoking and use of electronic cigarettes (vaping) in relation to preterm birth and small-for-gestational-age in a national US sample, 2016-2018

Introduction

The US experienced a surge in use of e-cigarettes. Smoking women may consider e-cigarettes during pregnancy as an alternative to smoking. E-cigarettes typically contain nicotine, an established cause of reduction in fetal growth in animal studies.

Methods

This cohort study included 99,201 mothers who delivered live singletons in 2016-2018 from the Pregnancy Risk Assessment Monitoring System. We created exposure categories based on self-reported number of cigarettes smoked per day and vaping frequency and evaluated their associations with preterm birth and small-for-gestational-age (SGA) birth (two established cigarette smoking-related risks).

Results

Dual users in late pregnancy were a heterogeneous group: 29% lightly smoked and occasionally vaped; 19% lightly smoked and frequently vaped; 36% heavily smoked and occasionally vaped; and 15% heavily smoked and frequently vaped. While dual users who heavily smoked and occasionally vaped had the highest adjusted OR for SGA (3.4, 95% CI 2.0, 5.7), all the dual users had, on average, about twice the odds of having SGA than non-users. While the risks of preterm birth were higher among sole light smokers (adjusted OR 1.3, 95% CI 1.1, 1.5) and sole heavy smokers (adjusted OR 1.5. 95% CI 1.2, 1.8) than non-users, the adjusted odds of preterm birth for dual users were not noticeably higher than those of non-users.

Conclusion

Relative to non-users, both smoking and vaping during pregnancy appear to increase risk of SGA, but excess risk of preterm birth appears to be primarily attributable to smoking alone. Higher levels of exposure tended to confer more risk.

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.

Nicotine Delivery and Pharmacokinetics of an Electronic Cigarette Compared With Conventional Cigarettes in Chinese Adult Smokers: A Randomized Open-Label Crossover Clinical Study

INTRODUCTION

To evaluate the nicotine pharmacokinetics of a commercial electronic cigarette (e-cigarette) relative to conventional cigarettes in Chinese adult smokers.

AIMS AND METHODS

A randomized, open-label, crossover clinical study was conducted on 23 healthy adult Chinese smokers. In two sessions, subjects used either the e-cigarettes with 30 mg/g nicotine in e-liquid or conventional cigarettes of a given brand, at one puff every 30 seconds for a total of 10 puffs. Blood samples were collected at specified time points for 4 hours after the first puff. Subjective effects on desire-to-smoke and physiological parameters such as heart rate and oxyhemoglobin saturation levels were also examined before and after using the two products.

RESULTS

The baseline-adjusted maximum nicotine concentration (Cmax-BL), time-to-peak nicotine concentration (Tmax), and nicotine absorption rate (Cmax-BL divided by Tmax) were found to be similar for the e-cigarette versus those of conventional cigarettes (p > .05). Total nicotine exposure measured as the area-under-curve (AUC0-t-BL) was significantly lower for the e-cigarette relative to that of conventional cigarettes. In addition, the subjects found that e-cigarettes were well tolerated under controlled puffing conditions.

CONCLUSIONS

The test e-cigarettes achieved similar nicotine delivery and pharmacokinetic profiles to those of the comparator cigarettes, indicating that this e-cigarette could be a potential alternative to conventional cigarettes for those adult smokers.

IMPLICATIONS

There are no data in the published literature on the nicotine pharmacokinetics of e-cigarettes in Chinese smokers. To the best of our knowledge, this is the first study to evaluate the nicotine delivery and pharmacokinetic profile of a commercial e-cigarette brand compared with conventional cigarettes in Chinese adult smokers. After the use of test e-cigarettes, nicotine delivery and pharmacokinetic profile were similar to those of conventional cigarettes in Chinese adult smokers.

The Impact of Current Tobacco Product Use Definitions on Estimates of Transitions Between Cigarette and ENDS Use

INTRODUCTION

Definitions of current tobacco and nicotine delivery product use vary and depend on frequency of use, established-use criteria, and the product type. Previous research has not considered how transition rates between current use of different products depend on the current use definition.

AIMS AND METHODS

We applied a multistate transition model to data on U.S. adults from waves 1-4 (2013-2017) of the Population Assessment of Tobacco and Health (PATH) study. We estimated transition rates between never, non-current, cigarette, electronic nicotine delivery systems (ENDS), and dual use states with and without established-use criteria (has smoked 100+ cigarettes in their lifetime; ever fairly regularly used ENDS) and different frequency thresholds (1+, 10+, 20+, and 30 days of the past 30 days). We considered use below a frequency threshold as either non-current use or a distinct, infrequent use category.

RESULTS

When treating use below a frequency threshold as non-current use, transition probability estimates were largely robust to the choice of use frequency threshold, although sole ENDS users were more likely to transition to non-current use or dual use as the current use threshold increased. Removing the established-use criterion for ENDS reduced the estimates of sole ENDS and dual users staying in their use state. When treating infrequent use as a separate category, transition probability estimates were dependent on the use frequency threshold, particularly transitions among the dual use states.

CONCLUSIONS

Product use definitions have important implications for assessing product use transitions and thus the public health implications of cigarette and ENDS control strategies.

IMPLICATIONS

How we define "current use" of tobacco and nicotine delivery products changes our estimates of how individuals transition to, between, and from different patterns of use. We show that the robustness of transition estimates to whether or not non-established users are included as current users and to different frequency-of-use threshold depends in part on whether low-frequency users are categorized as non-current users or as a distinct category. Our results emphasize the importance of intentional definitions of product use that reflect the larger goals of public health and tobacco control.

Associations of Demographics, Dependence, and Biomarkers With Transitions in Tobacco Product Use in a Cohort of Cigarette Users and Dual Users of Cigarettes and E-cigarettes

INTRODUCTION

It is uncertain whether e-cigarettes facilitate smoking cessation in the real world. We aimed to understand whether and how transitions among cigarette, e-cigarette, and dual use are associated with sociodemographics, dependence measures, and biomarkers.

AIMS AND METHODS

We followed 380 adult daily cigarette users and dual users every 2 months for up to 2 years. We estimated transition rates between noncurrent, cigarette-only, e-cigarette-only, and dual use states using a multistate transition model. We estimated univariable hazard ratios (HR) for demographics, dependence measures for cigarettes and e-cigarettes, biomarkers, spousal or partner behaviors, and other measures.

RESULTS

We estimated that participants transitioned from cigarette-only to e-cigarette-only through a period of dual use. Dual users ceased smoking (transitioning to e-cigarette-only use) at a greater rate than cigarette-only users did (HR 2.44, 95% CI: 1.49, 4.02). However, of the 60% of dual users estimated to transition to single product use in 1 year, 83% would transition to cigarette-only use and only 17% to e-cigarette-only use. E-cigarette dependence measures were generally associated with reduced e-cigarette cessation rather than enhanced cigarette cessation. E-cigarette users motivated by harm or toxicity reduction or because of restrictions on where or when they could smoke had reduced rates of smoking relapse. Cigarette dependence and spousal smoking were barriers to cigarette cessation for dual users, while using e-cigarettes first in the morning, motivation to quit smoking, and sensory, social, and emotional enjoyment of e-cigarettes (secondary dependence motives) were facilitators of smoking cessation among dual users.

CONCLUSIONS

Tobacco control policy and interventions may be informed by the barriers and facilitators of product transitions.

IMPLICATIONS

Although e-cigarettes have the potential to promote smoking cessation, their real-world impact is uncertain. In this cohort, dual users were more likely to quit smoking than cigarette-only users, but the overall impact was small because most dual users returned to cigarette-only use. Moreover, e-cigarette dependence promoted continued dual use rather than smoking cessation. Yet, high motivation to quit smoking and the sensory, social, and emotional enjoyment of e-cigarettes facilitated smoking cessation in dual users. Better understanding the barriers and facilitators of transitions can help to develop regulations and interventions that lead to more effective use of e-cigarettes for smoking cessation.

Vaping Aerosols from Vitamin E Acetate and Tetrahydrocannabinol Oil: Chemistry and Composition

The popularity of vaping cannabis products has increased sharply in recent years. In 2019, a sudden onset of electronic cigarette/vaping-associated lung injury (EVALI) was reported, leading to thousands of cases of lung illness and dozens of deaths due to the vaping of tetrahydrocannabinol (THC)-containing e-liquids that were obtained on the black market. A potential cause of EVALI has been hypothesized due to the illicit use of vitamin E acetate (VEA) in cannabis vape cartridges. However, the chemistry that modifies VEA and THC oil, to potentially produce toxic byproducts, is not well understood under different scenarios of use. In this work, we quantified carbonyls, organic acids, cannabinoids, and terpenes in the vaping aerosol of pure VEA, purified THC oil, and an equal volume mixture of VEA and THC oil at various coil temperatures (100-300 °C). It was found under the conditions of our study that degradation of VEA and cannabinoids, including Δ⁹-THC and cannabigerol (CBG), occurred via radical oxidation and direct thermal decomposition pathways. Evidence of terpene degradation was also observed. The bond cleavage of aliphatic side chains in both VEA and cannabinoids formed a variety of smaller carbonyls. Oxidation at the ring positions of cannabinoids formed various functionalized products. We show that THC oil has a stronger tendency to aerosolize and degrade compared to VEA at a given temperature. The addition of VEA to the e-liquid nonlinearly suppressed the formation of vape aerosol compared to THC oil. At the same time, toxic carbonyls including formaldehyde, 4-methylpentanal, glyoxal, or diacetyl and its isomers were highly enhanced in VEA e-liquid when normalized to particle mass.

Developmental Effects of Electronic Cigarette Use

Electronic cigarettes have gained widespread acceptance among adolescents and young adults. As a result of this popularity, there are concerns regarding the potential harm of primary, secondhand and thirdhand electronic cigarette exposures on fetal and postnatal development. In vitro studies have shown that constituents in electronic cigarette liquids, including nicotine, flavorings, and carrier agents can alter cellular processes and growth. Additionally, aerosolized electronic cigarette emissions have been shown to disrupt organ development and immune responses in preclinical studies. In clinical studies, an association between electronic cigarette use and frequent respiratory symptoms, greater asthma severity and impaired mucociliary clearance has been demonstrated with adolescent and young adult users of electronic cigarettes having twice the frequency of cough, mucus production, or bronchitis compared to nonusers. Along with the popularity of electronic cigarette use, secondhand electronic cigarette exposure has increased substantially; with almost one-fourth of middle and high school children reporting exposure to secondhand vapors. The health consequences of secondhand electronic cigarette exposure on children and other vulnerable populations are poorly understood but detectable levels of cotinine have been measured in nonusers. Pregnant women and their offspring are another vulnerable group at increased risk for health consequences from electronic cigarette exposure. Nicotine crosses the placenta and can disrupt brain and lung development in preclinical studies. This article will focus on the physiological and health effects associated with primary or secondhand exposure to electronic cigarettes. It is expected that with ongoing availability of electronic cigarettes as well as the accumulation of additional follow-up time for long-term outcomes, the risks associated with exposure will become better clarified. © 2022 American Physiological Society. Compr Physiol 12:3337-3346, 2022.

Proposed Standard Test Protocols and Outcome Measures for Quantitative Comparison of Emissions from Electronic Nicotine Delivery Systems

This study introduces and demonstrates a comprehensive, accurate, unbiased approach to robust quantitative comparison of electronic nicotine delivery systems (ENDS) appropriate for establishing substantial equivalence (or lack thereof) between inhaled nicotine products. The approach is demonstrated across a family of thirteen pen- and pod-style ENDS products. Methods employed consist of formulating a robust emissions surface regression model, quantifying the empirical accuracy of the model as applied to each product, evaluating relationships between product design characteristics and maximum emissions characteristics, and presenting results in formats useful to researchers, regulators, and consumers. Results provide a response surface to characterize emissions (total particulate matter and constituents thereof) from each ENDS appropriate for use in a computer model and for conducting quantitative exposure comparisons between products. Results demonstrate that emissions vary as a function of puff duration, flow rate, e-liquid composition, and device operating power. Further, results indicate that regulating design characteristics of ENDS devices and consumables may not achieve desired public health outcomes; it is more effective to regulate maximum permissible emissions directly. Three emissions outcome measures (yield per puff, mass concentration, and constituent mass ratio) are recommended for adoption as standard quantities for reporting by manufacturers and research laboratories. The approach provides a means of: (a) quantifying and comparing maximal emissions from ENDS products spanning their entire operating envelope, (b) comparative evaluation of ENDS devices and consumable design characteristics, and (c) establishing comparative equivalence of maximal emissions from ENDS. A consumer-oriented product emissions dashboard is proposed for comparative evaluation of ENDS exposure potential. Maximum achievable power dissipated in the coil of ENDS is identified as a potentially effective regulatory parameter.

Influence of Flavors and Nicotine Concentration on Nicotine Dependence in Adolescent and Young Adult E-Cigarette Users

Objective: The objective of this study is to examine the relationships between e-cigarette flavors, nicotine concentration, and their interaction on measures of nicotine dependence.Methods: Survey data are drawn from a cross-sectional convenience sample of past 30-day e-cigarette users aged 15 to 24 years (N = 2037) collected between October 2020 and November 2020. Participants were asked to provide information about the e-cigarette products they used most regularly. Only those with available information on flavors (fruit, mint, menthol/ice, and tobacco), nicotine concentration (0-2.9%, 3-4.9%, and 5% or greater), and time to first vape after waking (within 30 minutes, greater than 30 minutes) were included in analyses (N = 1430). Generalized linear regression models were used with log link and binary distribution to assess the relationship between flavors, nicotine concentration, and nicotine dependence. Effect modification by nicotine concentration was assessed using an interaction term for flavors by nicotine concentration. Models were adjusted for age, race/ethnicity, gender, and financial situation.Findings: Fruit, mint, and menthol flavor user groups had a very similar dose-response relationship between nicotine concentration and prevalence of vaping within 30 minutes. These groups showed that the prevalence of vaping within 30 minutes gradually increased as nicotine concentration increased. Meanwhile, tobacco flavor user groups demonstrated a decrease in prevalence of vaping within 30 minutes, as nicotine concentration increased.Conclusion: Results highlight the need for understanding how e-cigarette product characteristics like flavors and nicotine concentration can facilitate nicotine dependence to e-cigarettes. Findings suggest that comprehensive e-cigarette product regulation of all flavors and reducing nicotine concentration will help to reduce the risk for nicotine dependence among young people.

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.

Efficiency of Inhaled Cannabidiol in Cannabis Use Disorder: The Pilot Study Cannavap

INTRODUCTION

Cannabidiol (CBD), the second most prevalent cannabinoid found in cannabis, is considered to be safe for use. Studies suggest that CBD may be of benefit in treating cannabis use disorder (CUD). In clinical practice, CBD is already being used by patients who are trying to reduce or stop their cannabis consumption. The aim of this study was to assess the potential of CBD inhaled using a vaping device in CUD.

METHODS

This was an exploratory, observational, non-randomized, open-label study conducted at an Addiction Support and Prevention Center in Paris. The primary endpoint was a reduction of at least 50% in the reported number of joints consumed daily at 12 weeks. The participants were given an electronic cigarette along with liquid containing CBD. Nicotine at 6 mg/ml could be added in case of co-consumption of tobacco. They were assessed once a week and the CBD liquid dose was adjusted based on withdrawal signs and cravings (33.3, 66.6 or 100 mg/mL).

RESULTS

Between November 2020 and May 2021, 20 patients were included and 9 (45%) completed the follow-up. All of the participants used tobacco, and were provided a liquid with nicotine. At 12 weeks, 6 patients (30%) had reduced their daily cannabis consumption by at least 50%. The mean number of joints per day was 3, compared to 6.7 at baseline. The mean amount of CBD inhaled per day was 215.8 mg. No symptomatic treatment for cannabis withdrawal was prescribed. Mild adverse effects attributable to CBD and not requiring the prescription of any medicines were reported in a few patients.

CONCLUSION

This research provides evidence in favor of the use of CBD in CUD. It also highlights the benefits of inhalation as the route of CBD administration in patients who use cannabis: inhalation can allow users to self-titrate CBD based on their withdrawal symptoms and cravings. This study illustrates the interest of proposing an addictological intervention targeting at the same time tobacco and cannabis dependence in users who are co-consumers. A double-blind, randomized, placebo-controlled clinical trial is needed to assess the efficacy of inhaled CBD in CUD.Study registration number (IDRCB) issued by the ANSM (Agence nationale de sécurité du médicament et des produits de santé-French National Agency for Medicines and Health Products Safety): 2018-A03256-49. This study received IEC approval from the CPP Sud-Ouest et Outre-Mer 1 (South-West and Overseas 1 IEC) on 15/06/2020 (CPP 1-19-041/ID 3012).

A Literature Review and Framework Proposal for Halitosis Assessment in Cigarette Smokers and Alternative Nicotine-Delivery Products Users

Halitosis is a health condition which counts cigarette smoking (CS) among its major risk factors. Cigarette smoke can cause an imbalance in the oral bacterial community, leading to several oral diseases and conditions, including intraoral halitosis. Although the best approach to decrease smoking-related health risks is quitting smoking, this is not feasible for many smokers. Switching to potentially reduced-risk products, like electronic vapor products (EVP) or heated tobacco products (HTP), may help improve the conditions associated with CS. To date, there have been few systematic studies on the effects of CS on halitosis and none have assessed the effects of EVP and HTP use. Self-assessment studies have shown large limitations owing to the lack of reliability in the participants' judgment. This has compelled the scientific community to develop a strategy for meaningful assessment of these new products in comparison with cigarettes. Here, we compiled a review of the existing literature on CS and halitosis and propose a 3-layer approach that combines the use of the most advanced breath analysis techniques and multi-omics analysis to define the interactions between oral bacterial species and their role in halitosis both in vitro and in vivo. Such an approach will allow us to compare the effects of different nicotine-delivery products on oral bacteria and quantify their impact on halitosis. Defining the impact of alternative nicotine-delivery products on intraoral halitosis and its associated bacteria will help the scientific community advance a step further toward understanding the safety of these products and their potentiall risks for consumers.

Efficacy and safety of electronic cigarettes as a smoking cessation intervention: A systematic review and network meta-analysis

INTRODUCTION

This systematic review of randomized controlled trials (RCTs) evaluated the efficacy and safety of electronic cigarettes (e-cigarettes, ENDS) in helping people who smoke to achieve abstinence compared with electronic non-nicotine delivery systems (ENNDS, no nicotine) or any smoking cessation comparator treatment or combination of treatments at 24–26 weeks and at 52 weeks.

METHODS

Systematic review techniques involved searches of three databases in February 2020 with update searches run on 14 May 2021, two-person independent screening, two-person independent assessment of bias, formal extraction of data with verification by a second person, a feasibility assessment to decide if meta-analysis was appropriate, and network meta-analysis (NMA) of data at 24–26 weeks. Data at 52 weeks were narratively summarized.

RESULTS

Ten RCTs met the inclusion criteria, eight for efficacy and ten for safety. Eight of the nine RCTs were assessed as at high risk of bias. The sample sizes of the RCTs were 30–2012. Using nicotine replacement therapy (NRT) as the reference treatment, the incidences of smoking cessation at 24–26 weeks were comparable between ENDS and NRT groups (RR=1.17; 95% CrI: 0.66–1.86). Three sensitivity analyses were carried out indicating the main findings for 24–26 weeks were robust to assumptions. The findings at 52 weeks were inconclusive.

CONCLUSIONS

This systematic review and NMA indicates that there is no clear evidence of a difference in effect between nicotine containing e-cigarettes and NRT on incidences of smoking cessation at 24–26 weeks, and substantial uncertainty remains.

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.

Comparative Effects of E-Cigarette Aerosol on Periodontium of Periodontitis Patients

Introduction: Tobacco use is one of the main causes of periodontitis. E-cigarette are gaining in popularity, and studies are needed to better understand the impact of e-cigarettes on oral health. Objective: To perform a longitudinal study to evaluate the adverse effects of e-cigarettes on periodontal health. Methods: Naïve E-cigarette users, cigarette smokers, and non-smokers were recruited using newspaper and social media. Age, gender, and ethnicity, were recorded. Participants were scheduled for two visits 6 months apart. At each visit, we collected data on the frequency and magnitude of e-cigarette and cigarette use, and alcohol consumption. Carbon monoxide (CO) levels, cotinine levels, salivary flow rate, periodontal probing depth (PD), bleeding on probing (BoP), and clinical attachment loss (CAL) were also determined at both baseline and follow-up visits and compared between groups with two-way repeated measures ANOVA. Periodontal diagnosis and other categorical variables were compared between groups with the chi-square statistic and logistic regression. Results: We screened 159 subjects and recruited 119 subjects. One-hundred-one subjects (31 cigarette smokers, 32 e-cigarette smokers, and 38 non-smokers) completed every assessment in both visits. The retention and compliance rate of subjects was 84.9%. The use of social media and craigslist was significant in recruiting e-cigarette subjects. Ethnicity and race differed between groups, as did average age in the male subjects. Carbon monoxide and salivary cotinine levels were highest among cigarette smokers. Bleeding on probing and average PDs similarly increased over time in all three groups, but CAL uniquely increased in e-cigarette smokers. Rates of severe periodontal disease were higher in cigarette smokers and e-cigarette users than non-smokers, but interpretation is confounded by the older age of the cigarette smokers. Conclusion: Among the recruited participants, CAL after 6 months was significantly worse only in the e-cigarette smokers. This study design and protocol will assist in future larger studies on e-cigarette and oral health.

Further pharmacological characterization of a preclinical model of the early development of nicotine withdrawal

BACKGROUND

Establishing preclinical models of the development of nicotine withdrawal following acute nicotine exposure could inform tobacco addiction-related research, treatment, and policy. To this end, this lab has previously reported that rats exhibit withdrawal-like elevations in intracranial self-stimulation (ICSS) thresholds (anhedonia-like behavior) following acute nicotine exposure. The goal of this study was to provide further pharmacological characterization of ICSS as a measure of spontaneous and antagonist-precipitated withdrawal from acute nicotine.

METHODS AND RESULTS

Rats exhibited a small increase in ICSS thresholds over time following a single nicotine injection (1.0 mg/kg, s.c.), suggesting a modest spontaneous withdrawal effect (Experiment 1). In Experiment 2, the antidepressant bupropion (5.0 mg/kg, i.p.), which is used to treat tobacco addiction and attenuates nicotine withdrawal in both humans and rodents, blocked elevations in ICSS thresholds induced by a single injection of nicotine (0.5 mg/kg, s.c.) followed ≈ 2 h later by the non-selective, non-competitive nicotinic acetylcholine receptor (nAChR) antagonist mecamylamine (3.0 mg/kg, s.c.). In Experiment 3a, s.c. administration of the competitive, relatively selective α4ß2 nAChR antagonist dihydro-beta-erythroidine (DHßE) (5.6 mg/kg, but not 3.0 mg/kg) following each of 5 daily injections of nicotine (0.5 mg/kg, s.c.) elevated ICSS thresholds. Mecamylamine (3.0 mg/kg, s.c.) also elevated ICSS thresholds when administered following all 5 daily nicotine injections (0.5 mg/kg, s.c., Experiment 3b).

CONCLUSIONS

These findings provide further characterization of elevations in ICSS thresholds as a measure of withdrawal from acute nicotine exposure. Further use of these models may be useful for understanding the early development of nicotine withdrawal.

Electronic Nicotine Vapor Exposure Produces Differential Changes in Central Amygdala Neuronal Activity, Thermoregulation and Locomotor Behavior in Male Mice

Nicotine is an addictive substance historically consumed through smoking and more recently through the use of electronic vapor devices. The increasing prevalence and popularity of vaping prompts the need for preclinical rodent models of nicotine vapor exposure and an improved understanding of the impact of vaping on specific brain regions, bodily functions, and behaviors. We used a rodent model of electronic nicotine vapor exposure to examine the cellular and behavioral consequences of acute and repeated vapor exposure. Adult male C57BL/6J mice were exposed to a single 3-h session (acute exposure) or five daily sessions (repeated exposure) of intermittent vapes of 120 mg/ml nicotine in propylene glycol:vegetable glycerol (PG/VG) or PG/VG control. Acute and repeated nicotine vapor exposure did not alter body weight, and both exposure paradigms produced pharmacologically significant serum nicotine and cotinine levels in the 120 mg/ml nicotine group compared with PG/VG controls. Acute exposure to electronic nicotine vapor increased central amygdala (CeA) activity in individual neuronal firing and in expression of the molecular activity marker, cFos. The changes in neuronal activity following acute exposure were not observed following repeated exposure. Acute and repeated nicotine vapor exposure decreased core body temperature, however acute exposure decreased locomotion while repeated exposure increased locomotion. Collectively, these studies provide validation of a mouse model of nicotine vapor exposure and important evidence for how exposure to electronic nicotine vapor produces differential effects on CeA neuronal activity and on specific body functions and behaviors like thermoregulation and locomotion.

Vaping-Related Adverse Events and Perceived Health Improvements: A Cross-Sectional Survey among Daily E-Cigarette Users

Web-based samples of e-cigarette users commonly report significant vaping-related health improvements (HIs) and mild adverse events (AEs). This cross-sectional study with in-person interviewing data collection examined self-reported AEs and perceived HIs among Hungarian adult current daily exclusive e-cigarette (n = 65) and dual users (n = 127), and former daily e-cigarette users (n = 91) in 2018. Logistic regression was used to evaluate associations between reporting any AEs/HIs, vaping status, and covariates. More former users (52.7%) reported AEs than current users (39.6%; p = 0.038). Exclusive and dual daily users reported similar rates of AEs (44.6% and 37.0%, respectively; p = 0.308). More current users (46.9%) experienced HIs than former users (35.2%; p = 0.064). Exclusive daily users were more likely to report HIs than dual users (63.1% versus 38.6%; p = 0.001). Former user status and smoking cessation/reduction reasons increased the odds of reporting AEs, whereas nicotine-containing e-liquid use and older age decreased the odds of reporting AEs. Exclusive vaper status, using advanced generation devices, and smoking cessation/reduction reasons increased the odds of experiencing HIs. This study, which used a traditional data collection methodology, found a higher rate of AEs and a lower rate of HIs compared to web-based surveys. Our results highlight that experiencing AEs and HIs is affected by users’ characteristics, in addition to the device and e-liquid type.

Determination of (R)-(+)- and (S)-(-)-Nicotine Chirality in Puff Bar E-Liquids by 1H NMR Spectroscopy, Polarimetry, and Gas Chromatography-Mass Spectrometry

Tobacco products generally contain tobacco-derived nicotine (TDN; having ∼99+% (S)-(-)-nicotine). Recent United States regulation has led some producers to transition to synthetic ("tobacco-free") nicotine. For example, Puff Bar is now marketed with tobacco-free nicotine (TFN; presumed to be racemic). To evaluate the claim that these new products contain TFN, we evaluated the presence of the two nicotine optical isomers by 1H NMR spectroscopy, polarimetry, and gas chromatography-mass spectrometry. Older Puff Bars were found to contain (S)-(-)-nicotine, and newer "TFN" Puff Bars were found to contain both (R)-(+) and (S)-(-) isomers-indicating TFN, albeit with slightly more of the (S)-(-)-nicotine form.

Variations in Electronic Nicotine Delivery System (ENDS) device types and association with cigarette quit attempts

This study examined electronic nicotine delivery systems (ENDS) devices classified as disposable, non-refillable cartridge, refillable cartridge, refillable tank, and refillable mod systems and examined if cigarette quit attempts varied by device type among daily and non-daily ENDS users. Data from Wave 3 (2015-16) of the Population Assessment of Tobacco and Health Study, a nationally representative study in the U.S. was used to explore ENDS device types among past 12 month adult cigarette and ENDS users (n = 4952). Multivariate models were fitted to predict cigarette quit attempts among daily (n = 474) and nondaily (n = 1074) ENDS users by ENDS device types. Analyses were conducted in April 2020. Refillable tank system (38.5%) was the most prevalent and refillable cartridge was the least prevalent (3.3%) device type among past 12 month cigarette and ENDS users. Adults who used disposable ENDS were least likely to use ENDS as "an alternative to quitting all tobacco" (p < 0.001) or "as a way of cutting down on smoking" (p < 0.001). The odds of attempting to quit smoking were higher among daily ENDS users who used non-refillable cartridge (AOR = 7.3, 95% CI: 1.5-34.9), refillable tank (AOR = 5.3, 95% CI: 1.5-19.3) or refillable mod systems (AOR = 5.9, 95% CI: 1.2-30.1) compared to those who used disposables adjusting for age group, gender, race, ethnicity, and nicotine dependence. The likelihood of quit attempt among non-daily ENDS users did not differ by device type. Better understanding of ENDS device types and their use in smoking cessation is needed to inform health interventions.

Changes in puffing topography and subjective effects over a 2-week period in e-cigarette naïve smokers: Effects of device type and nicotine concentrations

INTRODUCTION

This study aimed to document changes in puffing topography and, the effects of device type and nicotine concentration on puffing topography, subjective effects and smoking behaviour over two weeks of e-cigarette (EC) use.

METHODS

EC naïve smokers (N = 50; 64% female) were randomly allocated to a cigalike (18 mg/mL) or tank containing either 18 (Tank18) or 6 mg/mL nicotine concentrations (Tank6). In 3 separate sessions (Baseline, 1 and 2 weeks post-baseline), participants vaped 20 min ad-libitum. Puff duration, puff number, inter-puff intervals (IPI), exhaled carbon monoxide (CO), cigarettes per day (CPD), cigarette dependence, craving, withdrawal, and subjective effects were recorded.

RESULTS

Two weeks post-baseline, puff duration and IPI significantly increased whilst puff number decreased. Cigalikes were associated with greater puff number and shorter IPI compared to Tanks; there was no difference between Tank18 and Tank6. CPD, CO and cigarette dependence reduced significantly from baseline to week1 but did not differ between conditions. During each session, there was a significant reduction in craving, whilst withdrawal symptoms were only alleviated in week1 and 2; there was no difference between conditions. Tank18 consistently rated highest on positive effects including satisfaction; satisfaction scores for Cigalikes and Tank6 declined overtime.

CONCLUSIONS

Cigalikes and tanks were both effective for reducing craving, withdrawal symptoms and CPD although for the former, this may only be achieved through more frequent puffing. That the Tank18 yielded greater satisfaction suggests tank devices and higher nicotine concentrations may be more suitable in the early stage of a smoking cessation attempt.

Changes in Biomarkers of Cigarette Smoke Exposure After 6 Days of Switching Exclusively or Partially to Use of the JUUL System with Two Nicotine Concentrations: A Randomized Controlled Confinement Study in Adult Smokers

Introduction

Evidence suggests that cigarette smokers who switch to electronic nicotine delivery systems (ENDS) reduce their exposure to harmful toxicants and carcinogens. It is unclear if dual-use is associated with decreases in exposure to toxicants.

Methods

This parallel-group confinement study assessed changes in biomarkers of exposure (BOEs) over six days among healthy adult smokers who were randomized into 1 of 11 study groups: eight JUUL-brand System (JUUL) groups (4 JUUL flavors [Virginia Tobacco, Menthol, Mint, Mango] × 2 nicotine concentrations [5.0% or 3.0% by weight]); Dual-Use group used preferred JUUL flavor (5.0% nicotine) and ≤50% usual brand (UB) cigarettes/day; UB Cigarette group and one group abstained from all tobacco/nicotine product use (Abstinence group). Urine and blood analysis assessed changes in primary BOE endpoints (NNAL, 3-HPMA, MHBMA, S-PMA COHb) and secondary BOE endpoints (NNN, HMPMA, CEMA, 1-OHP, O-toluidine, 2-NA, 4-ABP) among 279 adult smokers.

Results

In JUUL groups, median percent reductions in primary BOEs (Day 6–Baseline) were 90%–≥100% of Abstinence; there were no significant differences between JUUL groups and Abstinence. All reductions in JUUL groups were substantially and statistically significantly greater than reductions in the UB Cigarette group (ps < 0.025). Median reductions in primary BOEs in the Dual-Use group were 43%–55% of Abstinence. Similar results were observed for secondary BOEs.

Conclusion

This study suggests that the use of JUUL as a complete or partial substitute (i.e., dual-use with ≥50% reduction in cigarette consumption) for combustible cigarettes can substantially reduce exposure to multiple toxins associated with cigarette smoking.

Implications

This study adds to the growing body of evidence supporting the utility of ENDS products as potentially reduced-harm alternatives to cigarettes for adult smokers. Adult smokers who switched completely from cigarette smoking to use of the JUUL System (“JUUL”) in two nicotine concentrations (5.0% and 3.0%) and four flavors significantly reduced their exposure to multiple classes of cigarette-related toxicants. Additionally, smokers who used JUUL and continued smoking but reduced their daily cigarette consumption by ≥50% (dual users) also significantly reduced their toxicant exposure compared to cigarette smoking.

The Time Course of Compensatory Puffing With an Electronic Cigarette: Secondary Analysis of Real-World Puffing Data With High and Low Nicotine Concentration Under Fixed and Adjustable Power Settings

INTRODUCTION

In a secondary analysis of our published data demonstrating compensatory vaping behavior (increased puff number, puff duration, and device power) with e-cigarettes refilled with low versus high nicotine concentration e-liquid, here we examine 5-day time course over which compensatory behavior occurs under fixed and adjustable power settings.

AIMS AND METHODS

Nineteen experienced vapers (37.90 ± 10.66 years, eight females) vaped ad libitum for 5 consecutive days under four counterbalanced conditions (ie, 20 days in total): (1) low nicotine (6 mg/mL)/fixed power (4.0 V/10 W); (2) low nicotine/adjustable power; (3) high nicotine (18 mg/mL)/fixed power; (4) high nicotine/adjustable power (at 1.6 Ohm). Puff number, puff duration, and power settings were recorded by the device. For each day, total daily puffing time was calculated by multiplying daily puff number by mean daily puff duration.

RESULTS

A significant day × setting interaction revealed that whilst puffing compensation (daily puffing time) continued to increase over 5 days under fixed power, it remained stable when power settings were adjustable. Separate analysis for puff number and puff duration suggested that the puffing compensatory behavior was largely maintained via longer puff duration.

CONCLUSIONS

Under fixed power conditions (4.0 V/10 W), vapers appear to compensate for poor nicotine delivery by taking longer puffs and this compensatory puffing appears to be maintained over time.

IMPLICATIONS

Studies in smokers suggest that when switching to lower nicotine levels, compensation for poorer nicotine delivery is transient. Our novel findings suggest that vapers show a different pattern of compensation which is influenced by both nicotine strength and device power settings. When power is fixed (4.0 V; 10 W), compensation (via more intensive puffing) appears prolonged, persisting up to 5 days. Under adjustable settings when power is increased, puffing patterns remain stable over time. Implications of such compensatory behaviors for product safety and user satisfaction need further exploration.

Understanding potential mechanisms of harm: the drivers of electronic cigarette-induced changes in alveolar macrophages, neutrophils, and lung epithelial cells

Electronic (e-) cigarettes are growing in popularity despite uncertainties regarding their long-term health implications. The link between cigarette smoking and initiation of chronic lung disease took decades to unpick so in vitro studies mimicking e-cigarette exposure aim to detect early indicators of harm. In response to e-cigarette exposure, alveolar macrophages adopt a proinflammatory phenotype of increased secretion of proinflammatory cytokines, reduction in phagocytosis, and efferocytosis and reactive oxygen species generation. These effects are largely driven by free radical exposure, changes in PI3K/Akt signaling pathways, nicotine-induced reduction in phagocytosis receptors, and impaired lipid homeostasis leading to a foam-like lipid-laden phenotype. Neutrophils exhibit disrupted chemotaxis and transmigration to chemokines, reduced phagocytosis and bacterial killing, and an increase in protease secretion without corresponding antiproteases in response to e-cigarette exposure. This is driven by an altered ability to respond and to polarize toward chemoattractants, an activation of the p38 MAPK signaling pathway and inability to assemble NADPH oxidase. E-cigarettes induce lung epithelial cells to display decreased ciliary beat frequency and ion channel conductance as well as changes in chemokine secretion and surface protein expression. Changes in gene expression, mitochondrial function, and signaling pathways have been demonstrated in lung epithelial cells to explain these changes. Many functional outputs of alveolar macrophages, neutrophils, and lung epithelial cells have not been fully explored in the context of e-cigarette exposure and the underlying driving mechanisms are poorly understood. This review discusses current evidence surrounding the effects of e-cigarettes on alveolar macrophages, neutrophils, and lung epithelial cells with particular focus on the cellular mechanisms of change.

Impact of e-Liquid Composition, Coil Temperature, and Puff Topography on the Aerosol Chemistry of Electronic Cigarettes

E-cigarette aerosol is a complex mixture of gases and particles with a composition that is dependent on the e-liquid formulation, puffing regimen, and device operational parameters. This work investigated mainstream aerosols from a third generation device, as a function of coil temperature (315-510 °F, or 157-266 °C), puff duration (2-4 s), and the ratio of propylene glycol (PG) to vegetable glycerin (VG) in e-liquid (100:0-0:100). Targeted and untargeted analyses using liquid chromatography high-resolution mass spectrometry, gas chromatography, in situ chemical ionization mass spectrometry, and gravimetry were used for chemical characterizations. PG and VG were found to be the major constituents (>99%) in both phases of the aerosol. Most e-cigarette components were observed to be volatile or semivolatile under the conditions tested. PG was found almost entirely in the gas phase, while VG had a sizable particle component. Nicotine was only observed in the particle phase. The production of aerosol mass and carbonyl degradation products dramatically increased with higher coil temperature and puff duration, but decreased with increasing VG fraction in the e-liquid. An exception is acrolein, which increased with increasing VG. The formation of carbonyls was dominated by the heat-induced dehydration mechanism in the temperature range studied, yet radical reactions also played an important role. The findings from this study identified open questions regarding both pathways. The vaping process consumed PG significantly faster than VG under all tested conditions, suggesting that e-liquids become more enriched in VG and the exposure to acrolein significantly increases as vaping continues. It can be estimated that a 30:70 initial ratio of PG:VG in the e-liquid becomes almost entirely VG when 60-70% of e-liquid remains during the vaping process at 375 °F (191 °C). This work underscores the need for further research on the puffing lifecycle of e-cigarettes.

The impact of E-cigarette vaping and vapour constituents on bone health

BACKGROUND

In contrast to cigarettes, electronic cigarette use (E-cigarettes) has grown substantially over the last decade. This is due to their promotion as both a safer alternative to cigarettes and as an aide to stop smoking. Critically, upon E-cigarette use, the user may be exposed to high doses of nicotine in addition to other compounds including flavouring chemicals, metal particulates and carbonyl compounds, particularly in highly vascularised tissues such as bone. However, there has been limited investigation into the impact of E-cigarette usage on bone physiology, particularly over extended time periods and there are no clinical recommendations regarding E-cigarette usage in relation to orthopaedic surgery. This literature review draws together data from studies that have investigated the impact of E-cigarette vapour and its major constituents on bone, detailing the models utilised and the relevant mechanistic and functional results.

MAIN BODY

Currently there is a lack of studies both in vivo and in vitro that have utilised E-cigarette vapour, necessary to account for changes in chemical composition of E-cigarette liquids upon vaping. There is however evidence that human bone and bone cells express nicotine receptors and exposure of both osteoblasts and osteoclasts to nicotine, in high concentrations may reduce their viability and impair function. Similarly, it appears that aldehydes and flavouring chemicals may also negatively impact osteoblast viability and their ability to form bone. However, such functional findings are predominantly the result of studies utilising bone cell lines such as MG-63 or Saos-2 cells, with limited use of human osteoblasts or osteoclasts. Additionally, there is limited consideration for a possible impact on mesenchymal stem cells, which can also play an import role in bone repair.

CONCLUSION

Understanding the function and mechanism of action of the various components of E-cigarette vapour in mediating human bone cell function, in addition to long term studies to determine the potential harm of chronic E-cigarette use on human bone will be important to inform users of potential risks, particularly regarding bone healing following orthopaedic surgery and injury.

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.

Vapers exhibit similar subjective nicotine dependence but lower nicotine reinforcing value compared to smokers

INTRODUCTION

E-cigarette use has increased rapidly over the last 10 years, mostly among smokers and ex-smokers. Although there may be some degree of dependency on nicotine via e-cigarette use, the nature of this dependency is poorly understood. The aim of this paper is to use tasks from behavioural economics to compare the value that smokers place on tobacco cigarettes to the value that vapers place on e-cigarettes.

METHOD

Exclusive current smokers (n = 25) and vapers (n = 20) attended one session where they completed the Cigarette/e-cigarette Dependence Scale, the Cigarette/e-cigarette Purchasing Task (CPT) and the Concurrent Choice Task (CCT). The CPT requires participants to indicate how many puffs of their chosen product they would purchase at increasing price points. The CCT requires participants to choose between earning a money point or a point towards a cigarette/e-cigarette after being presented with a neutral, money or cigarette/e-cigarette cue.

RESULTS

Overall scores on the self-report scales suggest a comparable level of dependency between smokers and vapers. The CPT revealed that vapers are more sensitive than smokers to escalating costs as consumption declined as costs increased. On the CCT, when primed with money, vapers showed a decrease in choosing e-cigarettes.

CONCLUSION

These findings suggest that, on behavioural economic tasks, tobacco cigarettes have a higher relative value than e-cigarettes. Vapers appear to place a lower limit on what they will spend to access e-cigarettes and more readily choose money over e-cigarette puffs when primed by money cues.

Associated Changes in E-cigarette Puff Duration and Cigarettes Smoked per Day

INTRODUCTION

To examine whether changes in select measures of e-cigarette puffing topography are associated with changes in smoking behavior.

METHODS

Sixteen current cigarette smokers were instructed to completely switch from smoking combustible cigarettes to using e-cigarettes over a 2-week period. The study was completed in the Southern Midwestern region of the United States. Measures included demographics, smoking history, and cigarette dependence, as well as baseline and 2-week follow-up self-reported cigarettes per day, cigarette craving and urges, exhaled carbon monoxide readings, and e-cigarette usage data (puff number, puffing time, and average puff duration) collected via the e-cigarette built-in puff counter.

RESULTS

Over the 2-week switching period, participants significantly reduced their cigarettes per day (~80% reduction, p < .0001). Although the number of e-cigarette puffs/day remained relatively stable (p > .05), the average total e-cigarette daily puffing time increased significantly (p = .001). Users' average puff duration increased by 91 ms/puff/d (p < .001). The percentage decrease in cigarettes smoked per day was significantly and directly related to the slope of subjects' average puff duration over time (r(13) = .62, p = .01), such that as cigarettes per day decreased, puff duration increased. Self-reported smoking urges remained relatively stable from baseline to the end of the 2-week period (p > .05).

CONCLUSIONS

Among smokers switching to an e-cigarette, greater increases in e-cigarette puff duration was associated with greater reductions in cigarette smoking.

IMPLICATIONS

The current study is one of the first to examine changes in smokers' e-cigarette puffing behavior and associated changes in cigarette consumption as they attempt to completely switch to e-cigarettes. During a 2-week switching period, participants reduced their cigarettes per day. Moreover, although e-cigarette puffs per day remained relatively stable, users' average puff duration increased significantly. Greater increases in e-cigarette puff duration were associated with greater reductions in cigarette smoking. Understanding how to effectively use an e-cigarette to best reduce and eventually quit smoking will be necessary as smokers increasingly turn to these products to facilitate possible cessation.

Informing the development of adolescent e-cigarette cessation interventions: A qualitative study

INTRODUCTION

Adolescents are using e-cigarettes at high rates and there is limited information on how to help them quit. We aimed to inform e-cigarette cessation interventions by understanding why adolescents use and dislike e-cigarettes and their quit experiences.

METHODS

Six focus groups with current users (i.e., past-month use) and 2 focus groups with past users (i.e., no past-month use) were conducted in Fall 2019 in Connecticut (N = 62). We used a focus group guide and an iterative approach to identify themes.

RESULTS

Adolescents used e-cigarettes because of social reasons and to relieve stress and reported disliking e-cigarettes due to the cost, negative health effects, and addiction. They reported both intentional and unintentional experiences with quitting e-cigarettes. Reasons for unintentional quitting included lack of access to e-cigarettes. Reasons for intentional quitting included short-term "tolerance breaks" and health concerns. Of those who tried to quit, common quitting methods were "cold turkey," giving away their device, and limiting interactions with peer users. The most common withdrawal symptom was negative mood. Notable barriers to quitting included exposure to social influences at school, easy access to e-cigarettes, and lack of motivation to quit.

DISCUSSION

Our qualitative evidence suggests that e-cigarette cessation interventions need to motivate youth to quit, and teach them to manage social influences, stress and other negative mood, and withdrawal symptoms. Interventions that address social norms related to use of e-cigarettes in school and reduce cues related to e-cigarette use may also be beneficial.

E-cigarettes compromise the gut barrier and trigger inflammation

E-cigarette usage continues to rise, yet the safety of e-cigarette aerosols is questioned. Using murine models of acute and chronic e-cigarette aerosol inhalation, murine colon transcriptomics, and murine and human gut-derived organoids in co-culture models, we assessed the effects of e-cigarette use on the gut barrier. Histologic and transcriptome analyses revealed that chronic, but not acute, nicotine-free e-cigarette use increased inflammation and reduced expression of tight junction (TJ) markers. Exposure of murine and human enteroid-derived monolayers (EDMs) to nicotine-free e-cigarette aerosols alone or in co-culture with bacteria also causes barrier disruption, downregulation of TJ protein, and enhanced inflammation in response to infection. These data highlight the harmful effects of "non-nicotine" component of e-cigarettes on the gut barrier. Considering the importance of an intact gut barrier for host fitness and the impact of gut mucosal inflammation on a multitude of chronic diseases, these findings are broadly relevant to both medicine and public health.