Effects of Electronic Cigarette Liquid Nicotine Concentration on Plasma Nicotine and Puff Topography in Tobacco Cigarette Smokers: A Preliminary Report

What is the nicotine delivery profile of electronic cigarettes?

Introduction: Electronic cigarettes (e-cigarettes) are a rapidly evolving class of tobacco products intended to deliver nicotine to users. There are many types of e-cigarettes available and the most popular type today in the United States are 'pod' based devices that use high nicotine concentration liquids. Understanding the nicotine delivery capabilities of e-cigarettes is imperative for understanding their addictive potential and safety profile, informing regulation, and revealing their potential use as smoking cessation aids. Areas covered: This review discusses nicotine content of e-cigarettes, effectiveness of nicotine aerosolization by devices, delivery of nicotine to users, and user and device characteristics that impact each of these. Expert opinion: Modern e-cigarettes have the potential to deliver equal or more nicotine compared to a tobacco cigarette. Future research needs to identify the nicotine delivery profiles likely to benefit public health and the means to regulate them appropriately while also identifying those that are likely to cause harm. Public health benefit accrues if e-cigarettes help smokers quit combustible cigarettes completely. Harm is possible if inadequate nicotine delivery undermines cessation attempts, e-cigarettes facilitate continued combustible cigarette use, long-term e-cigarette use is associated with substantial morbidity/mortality, and/or e-cigarettes increase the initiation of combustible cigarette use among never smokers.

Changes in Puffing Topography and Nicotine Consumption Depending on the Power Setting of Electronic Cigarettes

Introduction

The study purpose was to evaluate changes in puffing topography of experienced electronic cigarette users (vapers) when changing power settings in electronic cigarette battery devices.

Methods

Experienced adult vapers (n = 21) were recruited. Participants used their own liquids and an atomizer and battery provided by the researchers. Two 30-minute sessions were performed, with the device power set at 6 W and 10 W, in a randomized, crossover, participant-blinded design. Puff number and duration (mean [SD]) were recorded in the provided electronic cigarette battery device, whereas the atomizers were weighted before and after use to determine liquid and nicotine consumption.

Results

Puff number and puff duration were lower at 10 W (46 [16] puffs and 3.8 [0.8] s) compared with 6 W (57 [20] puffs and 4.6 [1.0] s). Liquid and nicotine consumption was higher at 10 W (373 [176] mg and 4.2 [2.4] mg, respectively) compared with 6 W (308 [165] mg and 3.5 [2.3] mg, respectively). Vapers reported more aerosol volume and ease of use at 10 W compared with 6 W.

Conclusions

The study identified an attempt for compensatory puffing patterns and nicotine self-titration, with a change in puffing patterns (puff number and duration) observed when changing the power settings of an e-cigarette device.

Implications

Compensatory smoking behavior and nicotine self-titration is a well-established phenomenon. In electronic cigarettes, changing nicotine concentration in the liquid has been shown to trigger a compensatory puffing pattern. Herein, power setting of the electronic cigarette device was found to be a parameter associated with changes in puffing behavior, whereas higher power was preferable for the participants. These findings could contribute to the understanding of patterns of electronic cigarette use and could explain the preference of dedicated vapers to higher power devices. Additionally, laboratory studies evaluating aerosol emissions should consider using different puffing patterns according to the power settings tested.

Use of Flavored E-Cigarettes and the Type of E-Cigarette Devices Used among Adults and Youth in the US-Results from Wave 3 of the Population Assessment of Tobacco and Health Study (2015-2016)

The United States (U.S.) Food and Drug Administration has expressed concern about flavored e-cigarettes (e.g., JUUL brand) because they are appealing to youth who may be unaware that the product is addictive. The Population Assessment of Tobacco and Health Study Wave 3 provided data on flavor categories, type of e-cigarette product, and smoking status among past 30-day youth and adult e-cigarette users in the US. Most past 30-day youth and adult users reported using only one flavor category, with fruit (53% youth, 31% adult) being the most commonly reported category. Adults were far more likely to report using tobacco flavor alone, compared to any other individual flavor category or flavor category combinations (OR: 21.08, 95%CI: 5.92, 75.12). Whereas, youth were more likely to report using multiple flavor categories (OR: 2.03, 95%CI: 1.55, 2.65), with the most reported pairing being fruit and candy (36%). The variety of flavors on the market appeals to consumers of all ages. Although most past 30-day e-cigarette users reported only one flavor category, non-tobacco flavors were far more common among youth. Differences in flavor preferences among adult versus youth vapers may have implications for the role of flavors in both the initiation of youth vaping and adult vaping for smoking cessation.

A mouse model for chronic intermittent electronic cigarette exposure exhibits nicotine pharmacokinetics resembling human vapers

Electronic cigarettes (E-cig) use is increasing rapidly, particularly among youths. Animal models for E-cig exposure with pharmacokinetics resembling human E-cig users are lacking. We developed an E-cig aerosol exposure system for rodents and a chronic intermittent delivery method that simulates E-cig users who vape episodically during wakefulness and abstain during sleep. Mice were exposed to E-cig in a programmed schedule at very low, low, medium, or high doses defined by duration of each puff, number of puffs per delivery episode and frequency of episodes in the dark phase of a 12/12-h circadian cycle for 9 consecutive days. The plasma nicotine/cotinine levels and their time courses were determined using LC/MS-MS. We assessed the body weight, food intake and locomotor activity of Apolipoprotein E null (ApoE-/-) mice exposed to chronic intermittent E-cig aerosol. Plasma nicotine and cotinine levels were positively correlated with exposure doses. Nicotine and cotinine levels showed a circadian variation as they increased with time up to the maximum nicotine level of 21.8 ± 7.1 ng/mL during the daily intermittent E-cig exposure in the 12-h dark phase and then declined during the light phase when there was no E-cig delivery. Chronic E-cig exposure to ApoE-/- mice decreased body weight, food intake and increased locomotion. Our rodent E-cig exposure system and chronic intermittent exposure method yield clinically relevant nicotine pharmacokinetics associated with behavioral and metabolic changes. The methodologies are essential tools for in vivo studies of the health impacts of E-cig exposure on CNS, cardiovascular, pulmonary, hepatic systems, metabolism and carcinogenesis.

Use of social media to establish vapers puffing behaviour: Findings and implications for laboratory evaluation of e-cigarette emissions

The recent growth in e-cigarette use has presented many challenges to Public Health research, including understanding the potential for e-cigarettes to generate toxic aerosol constituents during use. Recent research has established that the way e-cigarettes are puffed influences the magnitude of emissions from these devices, with puff duration the dominant driving force. Standardised puffing machine methods are being developed to harmonise testing approaches across laboratories, but critical to their success is the degree with which they accurately reflect vapers real-world puffing behaviours (topography). Relatively limited data is available examining the way vapers puff, with significant inconsistencies between studies. Here we report the creation and analysis of a large database of public-domain vaping videos to establish e-cigarettes puffing behaviour in near natural settings. Over 300 videos containing 1200 puffing events from 252 vapers were obtained from social media sources, divided approximately equally amongst cigalike, Ego and Advanced Personal Vapouriser ("APV", also referred to as "boxmod") types of e-cigarettes. Analysis showed that similar mean puff durations were found for all three categories of vaping devices. This includes direct-to-lung as well as mouth-to-lung puffing behaviours. A 3 s puff duration, as used in the recently published ISO puffing standard ISO 20,768:2018, appears appropriate for average behaviours. However, the wide diversity of puffing durations observed amongst vapers means it may be challenging to identify a simple yet comprehensively representative single machine-puffing regimen for laboratory studies. A puff duration of around 5.6 s appears to represent 95th percentile puffing behaviours amongst vapers and may be an appropriate choice for scientists and regulators seeking an additional more intense puffing regime. A range of new behavioural patterns have been identified whose impact on aerosol exposure need to be considered. Public-domain video records of vapers provides valuable and accessible insights into real-world use behaviours. It is freely available, and constantly updated with new material, and therefore provides a valuable resource for scientists seeking to understand real-world vaping behaviours.

Tobacco and bone fractures: A review of the facts and issues that every orthopaedic surgeon should know

Objectives

The aim of this study was to review the impact of smoking tobacco on the musculoskeletal system, and on bone fractures in particular.

Methods

English-language publications of human and animal studies categorizing subjects into smokers and nonsmokers were sourced from MEDLINE, The Cochrane Library, and SCOPUS. This review specifically focused on the risk, surgical treatment, and prevention of fracture complications in smokers.

Results

Smokers have an increased risk of fracture and experience more complications with delayed bone healing, even if they have already stopped smoking, because some adverse effects persist for a prolonged period. Some risks can be reduced during and after surgery by local and general prevention, and smoking cessation is an important factor in lessening this risk. However, if a patient wants to stop smoking at the time of a fracture, the cessation strategies in reducing tobacco use are not easy to implement. The patient should also be warned that using e-cigarettes or other tobaccos does not appear to reduce adverse effects on health.

Conclusion

The evidence reviewed in this study shows that smoking has a negative effect in terms of the risk and treatment of fractures.

Cite this article: J. Hernigou, F. Schuind. Tobacco and bone fractures: A review of the facts and issues that every orthopaedic surgeon should know. Bone Joint Res 2019;8:255–265. DOI: 10.1302/2046-3758.86.BJR-2018-0344.R1.

Cigarettes, E-cigarettes, and Adolescents' Oral Health: Findings from the Population Assessment of Tobacco and Health (PATH) Study

INTRODUCTION

Adolescents are a population group that actively uses tobacco products; however, limited reports are available on the effects of tobacco products on adolescents' oral health.

OBJECTIVES

This study investigated associations between self-reported use of cigarettes and e-cigarettes on the oral health status of a representative sample of US adolescents.

METHODS

Data came from 13,650 adolescents aged 12 to 17 y who participated in the 2013-2014 wave of the Population Assessment of Tobacco and Health study. Participants self-reported current use (i.e., past 30 d) and ever use of cigarettes and e-cigarettes, as well as past-year diagnoses with dental problems by a doctor, dentist, or other health professional (self-reported by parent or emancipated youth). Survey-adjusted logistic regression was used to estimate prevalence odds ratios (PORs) and 95% CIs.

RESULTS

The proportion of adolescents who self-reported current use of only cigarettes was 3.2%, while 1.7% reported current use of only e-cigarettes. Similarly, 1.4% reported current use of both cigarettes and e-cigarettes, while 7.1% reported ever use of both. About 22% self-reported a provider diagnosis with dental problems in the past year. The covariate-adjusted associations between current cigarette and e-cigarette use on self-reported provider-diagnosed dental problems in the past year were, respectively, POR = 1.50 (95% CI, 1.18 to 1.90) and POR = 1.11 (95% CI, 0.79 to 1.55), while self-reported current use of both was associated with POR = 1.72 (95% CI, 1.24 to 2.38). Ever use of cigarettes and e-cigarettes was likewise associated with increased prevalence odds of self-reported past-year diagnosis with dental problems, although to a lesser magnitude.

CONCLUSION

Findings suggest that dual use of e-cigarettes and conventional cigarettes is associated with poor oral health outcomes among adolescents. However, studies of a longitudinal nature are needed to confirm these findings.

KNOWLEDGE TRANSFER STATEMENT

The results of this study are relevant to public health and oral health practitioners seeking to intervene during developmental periods in which adolescents may have access to tobacco products in the home and in social settings.

Mitochondrial Stress Response in Neural Stem Cells Exposed to Electronic Cigarettes

Stem cells provide a sensitive model to study exposure to toxicants, such as cigarette smoke. Electronic cigarettes (ECs) are popular nicotine delivery devices, often targeted to youth and pregnant mothers. However, little is known about how chemicals in ECs might affect neural stem cells, and in particular their mitochondria, organelles that maintain cell functionality and health. Here we show that the mechanism underlying EC-induced stem cell toxicity is stress-induced mitochondrial hyperfusion (SIMH), a transient survival response accompanied by increased mitochondrial oxidative stress. We identify SIMH as a survival response to nicotine, now widely available in EC refill fluids and in pure form for do-it-yourself EC products. These observed mitochondrial alterations combined with autophagy dysfunction to clear damaged mitochondria could lead to faulty stem cell populations, accelerate cellular aging, and lead to acquired mitochondriopathies. Any nicotine-containing product may likewise stress stem cells with long-term repercussions for users and passively exposed individuals. VIDEO ABSTRACT.

Influence of Electronic Cigarette Characteristics on Susceptibility, Perceptions, and Abuse Liability Indices among Combustible Tobacco Cigarette Smokers and Non-Smokers

This study assessed how electronic cigarette (ECIG) characteristics amenable to regulation-namely nicotine content, flavor, and modified risk messages-impact ECIG use susceptibility, harm/addiction perceptions, and abuse liability indices among combustible tobacco cigarette (CTC) smokers and non-smokers. CTC smokers and non-smokers varying in ECIG use recruited via Amazon Mechanical Turk (MTurk) completed an online survey in 2016 (analytic n = 706). Participants were randomly assigned to one of eight conditions differing in ECIG characteristics: nicotine content (no, low, high), flavor (menthol, tobacco, fruit), or modified risk message (reduced harm, reduced carcinogen exposure). Regressions assessed ECIG susceptibility, harm/addiction perceptions, and abuse liability indices (purchase task measures of breakpoint/intensity) within each regulatory domain (nicotine content, flavor, message) and their interactions with CTC/ECIG status. Differential effects on ECIG susceptibility, harm/addiction perceptions, and abuse liability indices were observed by regulatory domain with many effects moderated by CTC/ECIG status. ECIG nicotine content and flavor conditions were the most influential across outcomes. Greater nicotine content, tobacco-flavored and reduced carcinogen exposure ECIGs were more highly preferred by CTC smokers with some differing preferences for non-users. Findings reinforce consideration of discrete ECIG preferences across tobacco use status to improve regulatory efficacy.

A Pilot Study of E-Cigarette Naïve Cigarette Smokers and the Effects on Craving After Acute Exposure to E-Cigarettes in the Laboratory

BACKGROUND AND OBJECTIVES

Recent surveys confirm continued increases in the use of electronic-cigarettes (e-cigarettes) in adolescents and adults. Users often state that e-cigarettes reduce tobacco craving and withdrawal symptoms in addition to their smoking. Data from laboratory studies and clinical trials have confirmed these statements, though there are inconsistencies in the outcomes. In this pilot study, we set out to evaluate the effects of e-cigarettes, as compared to the participants' own cigarettes, on baseline craving and smoking severity.

METHODS

Using a within-subjects, placebo-controlled study design, 15 tobacco-dependent, e-cigarette naïve participants sustained abstinence overnight. They completed distinct phases of this protocol during four separate study sessions. Participants were randomized to an e-cigarette device containing one of three doses of nicotine (0, 18, or 36 mg/ml) or their own cigarette. Each study visit was ~3 hours long and separated by at least 7 days. Visits included assessments of craving and smoking severity.

RESULTS

The data showed that after 10 puffs in both the Own cigarette and e-cigarette conditions, breath carbon monoxide levels increased significantly in the former but not the latter. Questionnaire of Smoking Urges and Choices to Smoke scores were not statistically different across groups after two distinct bouts of 10 puffs each. Additionally, E-cigarette Perceptions Questionnaire responses were not significantly different according to dose.

CONCLUSION AND SCIENTIFIC SIGNIFICANCE

This experiment provides data demonstrating that e-cigarettes did not reduce craving or smoking severity in e-cigarette naïve users. However, since this was a pilot study, the conclusions that can be drawn are limited. (Am J Addict 2019;28:361-366).

Discrimination of nicotine content in electronic cigarettes

INTRODUCTION

Behavioral discrimination of nicotine has only recently been assessed in humans, administered mostly by nasal spray before the newly available Spectrum research cigarettes differing in nicotine content. Here we wanted to explore applicability of these procedures to assess discrimination of nicotine administered by e-cigarettes.

METHODS

In this feasibility study, 16 adult smokers were tested on ability to discriminate e-cigarettes with nicotine concentrations of 36, 24, and 12 mg/ml, one per session (in that order), from a placebo (0 mg/ml), each identified only by letter code. Reliable discrimination was defined by accurately identifying which was which (i.e. nicotine vs placebo) on >85% of trials (i.e. ≥7 of 8; p < .05). Subjective perceptions were also assessed.

RESULTS

Discrimination from placebo was shown with 36 mg/ml and with 24 mg/ml nicotine in 15 of 16 subjects, but only 10 discriminated placebo from 12 mg/ml nicotine. Subjective items previously related to acute nicotine exposure ("how much nicotine", "head rush/buzzed" on 0-100 VAS) generally showed nicotine concentration-dependent effects, as expected, but so did "throat irritation".

CONCLUSIONS

Preliminary results confirm feasibility of using our behavioral procedure to assess ability to discriminate nicotine administered via these e-cigarettes, broadening generalizability of this procedure beyond nicotine via nasal spray and smoked tobacco cigarettes. Findings also suggest its applicability with testing discrimination of nicotine via other methods of rapid dosing (e.g., hookah, novel products), including the newer e-cigarette products. Further study with larger samples may identify individual difference and other factors influencing nicotine discrimination administered via e-cigarettes and other products.

Electronic Cigarettes: Trends, Health Effects and Advising Patients Amid Uncertainty

Dental professionals can be effective tobacco prevention and cessation partners. Electronic cigarettes (e-cigarettes), which deliver aerosolized nicotine but fewer toxicants than found in cigarette smoke, present new and contentious questions for clinicians, patients, and researchers. Evidence suggests e-cigarettes are not harmless but are less dangerous than cigarettes. Smoking cessation effectiveness is unproven and oral and systemic health effects remain under study. Dental professionals must stay informed to provide patients truthful information as new data emerge.

Young adult dual combusted cigarette and e-cigarette users' anticipated responses to hypothetical e-cigarette market restrictions

Introduction: The aim of this exploratory study was to assess young adult dual e-cigarette (EC) and combusted cigarette (CC) users' anticipated responses to hypothetical market restrictions regarding key EC characteristics. Methods: Data came from 240 young adult dual EC and CC users recruited via Amazon Mechanical Turk in June 2017. Descriptive statistics were used to report sociodemographic, CC smoking, and EC use characteristics. McNemar's chi-square tests and chi-square tests were used to assess differences between groups in terms of anticipated responses to hypothetical EC market restrictions. Results: Hypothetical regulations resulted in reported intentions to reduce EC use and increase CC use; the greatest impact was found for restrictions regarding e-liquid nicotine content, followed by flavor and ability to modify EC devices. Moreover, individuals reporting use of flavored e-liquid, high nicotine content e-liquid, and customizable EC were most likely to report intentions to reduce EC use and increase CC use. Conclusions: This work provides preliminary evidence that restrictive regulations regarding key EC characteristics may increase intentions to increase CC use among young adult dual EC and CC users.

Emissions of Free Radicals, Carbonyls, and Nicotine from the NIDA Standardized Research Electronic Cigarette and Comparison to Similar Commercial Devices

E-cigarettes (e-cigs) are a diverse and continuously evolving group of products with four generations currently in the market. The National Institute on Drug Abuse (NIDA) standardized research e-cigarette (SREC) is intended to provide researchers with a consistent e-cig device with known characteristics. Thus, we conducted laboratory-based characterizations of oxidants and nicotine in aerosols produced from SREC and other closed-system, breath-activated, commercially available e-cigs (Blu and Vuse). We hypothesized that oxidant and nicotine production will be significantly affected in all devices by changes in puffing parameters. All e-cigs were machine vaped and the aerosols generated were examined for nicotine, carbonyls, and free-radicals while varying the puff-volumes and puff-durations to reflect typical human usage. The data were normalized on a per puff, per gram aerosol, and per milligram nicotine basis. We found that aerosol production generally increased with increasing puff-duration and puff-volume in all e-cigs tested. Increased puff-duration and puff-volume increased nicotine delivery for Blu and Vuse but not the SREC. We report, for the first time, reactive free-radicals in aerosols from all closed-system e-cigs tested, albeit at levels lower than cigarette smoke. Formaldehyde, acetaldehyde, acetone, and propionaldehyde were detected in the aerosols of all tested e-cigs. Carbonyl and free radical production is affected by puff-duration and puff volume. Overall, SREC was more efficient at aerosol and nicotine production than both Blu and Vuse. In terms of carbonyl and free radical levels, SREC delivered lower or similar levels to both other devices.

JUUL: Spreading Online and Offline

PURPOSE

The increasing popularity of the JUUL electronic nicotine delivery system among youth poses several potential public health concerns. Social media can be used to better understand the spread of information related to JUUL. This study examined whether adolescents (age < 18) are following JUUL's official Twitter account and subsequently sharing (retweeting) JUUL's posts to their followers. We also assessed various patterns in which adolescents share information on JUUL with each other.

METHODS

We collected 3,239 tweets from JUUL's official Twitter account (@JUULVapor) for one full year from February 2017 to January 2018. These tweets were shared by Twitter users to their followers 1,124times by 721 unique users. Users were determined to be either adolescent (age <18) or adult (≥18) based on a systematic procedure involving double coding. We used social network analysis to explore the relationships between users retweeting JUUL.

RESULTS

One-quarter (25%) of users were determined to be adolescents. Social network analysis revealed a maximum path length of 4 and a positive assortativity (r = .29). There were 25 (9%) instances of an adolescent retweeting content from another adolescent, 35 (12%) of an adolescent retweeting from an adult, and 30 (11%) of an adult retweeting from an adolescent.

CONCLUSIONS

JUUL's official Twitter account is being followed-and its messages are being shared-by adolescents. Rigorous policies and prevention programs are needed to curb adolescent exposure to JUUL content and discussions online.

Electronic Cigarettes: Impact on Lung Function and Fractional Exhaled Nitric Oxide Among Healthy Adults

Electronic cigarettes (e-cigarettes) are rapidly becoming an alternative form of nicotine consumption worldwide and a disruptive element in the global health diplomacy. This study aimed to investigate the impact of e-cigarettes on lung function and fractional exhaled nitric oxide (FeNO) among young healthy male adults. Sixty apparently healthy male volunteers were recruited and divided into two groups. Group 1 (e-cigarette-exposed group) consisted of 30 males who were daily e-cigarette users (age 27.07 ± 6.00 [mean ± SD] years). Group 2 (control group) consisted of 30 males who were not e-cigarette users (age 25.90 ± 7.72 [mean ± SD] years). Both groups were neither current nor former traditional tobacco users. Age, ethnicity, height, weight, and socioeconomic status were considered using a matched design to investigate the impact of e-cigarette use on lung function and FeNO. The lung function test parameters that were found to be significantly decreased in e-cigarette users compared to their control group were forced expiratory volume in the first second (FEV₁), forced expiratory ratio (FEV₁/FVC), forced expiratory flow—25% (FEF_25%), forced expiratory flow—50% (FEF_50%), forced expiratory flow—75% (FEF_75%), forced expiratory flow—25%–75% (FEF_25%–75%), and forced expiratory flow—75%–85% (FEF_75%–85%). FeNO was also decreased in e-cigarette users, but it did not reach the level of significance. The use of e-cigarettes significantly impaired various lung function parameters and the pattern of impairment exhibited a peripheral obstructive airway involvement. These findings have a general message for the global health community on the potential harm of e-cigarettes on lung function.

Triangulating abuse liability assessment for flavoured cigar products using physiological, behavioural economic and subjective assessments: a within-subjects clinical laboratory protocol

INTRODUCTION

In the USA, Food and Drug Administration regulations prohibit the sale of flavoured cigarettes, with menthol being the exception. However, the manufacture, advertisement and sale of flavoured cigar products are permitted. Such flavourings influence positive perceptions of tobacco products and are linked to increased use. Flavourings may mask the taste of tobacco and enhance smoke inhalation, influencing toxicant exposure and abuse liability among novice tobacco users. Using clinical laboratory methods, this study investigates how flavour availability affects measures of abuse liability in young adult cigarette smokers. The specific aims are to evaluate the effect of cigar flavours on nicotine exposure, and behavioural and subjective measures of abuse liability.

METHODS AND ANALYSES

Participants (projected n=25) are healthy smokers of five or more cigarettes per day over the past 3 months, 18-25 years old, naive to cigar use (lifetime use of 50 or fewer cigar products and no more than 10 cigars smoked in the past 30 days) and without a desire to quit cigarette smoking in the next 30 days. Participants complete five laboratory sessions in a Latin square design with either their own brand cigarette or a session-specific Black & Mild cigar differing in flavour (apple, cream, original and wine). Participants are single-blinded to cigar flavours. Each session consists of two 10-puff smoking bouts (30 s interpuff interval) separated by 1 hour. Primary outcomes include saliva nicotine concentration, behavioural economic task performance and response to various questionnaire items assessing subjective effects predictive of abuse liability. Differences in outcomes across own brand cigarette and flavoured cigar conditions will be tested using linear mixed models.

ETHICS AND DISSEMINATION

The Virginia Commonwealth University Institutional Review Board approved the study (VCU IRB: HM20007848). Dissemination channels for study findings include scientific journals, scientific meetings, and policy briefs.

TRIAL REGISTRATION NUMBER

NCT02937051.

'Real-world' compensatory behaviour with low nicotine concentration e-liquid: subjective effects and nicotine, acrolein and formaldehyde exposure

AIMS

To compare the effects of (i) high versus low nicotine concentration e-liquid, (ii) fixed versus adjustable power and (iii) the interaction between the two on: (a) vaping behaviour, (b) subjective effects, (c) nicotine intake and (d) exposure to acrolein and formaldehyde in e-cigarette users vaping in their everyday setting.

DESIGN

Counterbalanced, repeated measures with four conditions: (i) low nicotine (6 mg/ml)/fixed power; (ii) low nicotine/adjustable power; (iii) high nicotine (18 mg/ml)/fixed power; and (iv) high nicotine/adjustable power.

SETTING

London and the South East, England.

PARTICIPANTS

Twenty experienced e-cigarette users (recruited between September 2016 and February 2017) vaped ad libitum using an eVic Supreme™ with a 'Nautilus Aspire' tank over 4 weeks (1 week per condition).

MEASUREMENTS

Puffing patterns [daily puff number (PN), puff duration (PD), interpuff interval (IPI)], ml of e-liquid consumed, changes to power (where permitted) and subjective effects (urge to vape, nicotine withdrawal symptoms) were measured in each condition. Nicotine intake was measured via salivary cotinine. 3-Hydroxypropylmercapturic acid (3-HPMA), a metabolite of the toxicant acrolein, and formate, a metabolite of the carcinogen formaldehyde, were measured in urine.

FINDINGS

There was a significant nicotine concentration × power interaction for PD (P < 0.01). PD was longer with low nicotine/fixed power compared with (i) high nicotine/fixed power (P < 0.001) and (ii) low nicotine/adjustable power (P < 0.01). PN and liquid consumed were higher in the low versus high nicotine condition (main effect of nicotine, P < 0.05). Urge to vape and withdrawal symptoms were lower, and nicotine intake was higher, in the high nicotine condition (main effects of nicotine: P < 0.01). While acrolein levels did not differ, there was a significant nicotine × power interaction for formaldehyde (P < 0.05).

CONCLUSIONS

Use of a lower nicotine concentration e-liquid may be associated with compensatory behaviour (e.g. higher number and duration of puffs) and increases in negative affect, urge to vape and formaldehyde exposure.

Nicotine pharmacokinetics of electronic cigarettes: A review of the literature

E-cigarettes are battery-powered electronic devices from which users can inhale nicotine following its aerosolisation from a liquid solution. Some regulators and public health bodies consider e-cigarettes as potentially playing a major role in tobacco harm reduction. Their ability to provide nicotine to smokers in both amount and in a manner and form generally similar to cigarette smoking have been proposed as key components to help smokers reduce or cease the use of combustible cigarettes. Nicotine pharmacokinetic studies of e-cigarettes have been performed for a number of years and are beginning to show how nicotine delivery is evolving as the products themselves evolve. In this review, we provide a critical overview of the literature to describe what is known about nicotine delivery from e-cigarettes. We will discuss how the progression of e-cigarette design, development, and user familiarity has allowed increases in nicotine availability to the user, in the context of how much and how rapidly nicotine is delivered during acute-use periods. This review will also provide insight into current research gaps and highlight the potential utility of modelling and the standardisation of methodologies used to assess nicotine delivery to facilitate identification of products that are best suited to displace cigarette smoking among adult smokers.

Electronic cigarette liquid and device parameters and aerosol characteristics: A survey of regular users

INTRODUCTION

Electronic cigarettes are widely variable devices, typically with user definable liquid and device parameters. Yet, little is known about how regular users manipulate these parameters. There is also limited understanding of what factors drive electronic cigarette use and liquid purchasing, and whether two common ingredients, propylene glycol and vegetable glycerin, alter the subjective effects of these devices.

METHODS

During the spring of 2016 522 adults, who reported daily use of electronic cigarettes containing nicotine, completed a survey on electronic cigarettes. Survey questions included an electronic cigarette dependence questionnaire, questions on tobacco and electronic cigarette use, and device and liquid preferences.

RESULTS

Fifty-nine percent of respondents reported using another tobacco product, which was positively associated with level of nicotine dependence. On average, devices were set to 28.3 (SD = 24.2) watts. Ability to change device voltage, and level of resistance typically used, was significantly associated with level of nicotine dependence. Amount of liquid consumed, nicotine concentration, and milligrams of nicotine used per week, were positively associated with nicotine dependence. Participants rated 'good taste' as the most important consideration when using and purchasing liquids, and propylene glycol is associated with undesirable effects and vegetable glycerin with desirable effects.

CONCLUSIONS

These data indicate that electronic cigarette users utilize a wide range device parameter settings and liquid variables, and that individuals with greater nicotine dependence favor voltage control devices, and lower resistance heating elements. Taste is a key factor for electronic cigarette selection, and concentrations of propylene glycol and vegetable glycerin may have a significant impact on the reinforcing effects of liquids.

Impact of e-liquid flavors on e-cigarette vaping behavior

OBJECTIVE

The primary objective of this pilot study was to describe the impact of e-cigarette liquid flavors on experienced e-cigarette users' vaping behavior.

METHODS

11 males and 3 females participated in a 3-day inpatient crossover study using e-cigarettes with strawberry, tobacco, and their usual brand e-liquid. Nicotine levels were nominally 18 mg/mL in the strawberry and tobacco e-liquids and ranged between 3-18 mg/mL in the usual brands. On each day, participants had access to the study e-cigarette (KangerTech mini ProTank 3, 1.5 Ohms, 3.7 V) and the assigned e-liquid during a 90-minute videotaped ad libitum session.

RESULTS

Average puff duration was significantly longer when using the strawberry e-liquid (3.2 ± 1.3 s, mean ± SD) compared to the tobacco e-liquid (2.8 ± 1.1 s) but the average number of puffs was not significantly different (strawberry, 73 ± 35; tobacco, 69 ± 46). Compared to the strawberry- and tobacco-flavored e-liquids, average puff duration was significantly longer (4.3 ± 1.6 s) and the average number of puffs was significantly higher (106 ± 67 puffs) when participants used their usual brand of e-liquid. Participants generally puffed more frequently in small groups of puffs (1-5 puffs) with the strawberry compared to the tobacco e-liquid and more frequently in larger groups (>10 puffs) with their usual brand. The strength of the relationship between vaping topography and nicotine intake and exposure were not consistent across e-liquids.

CONCLUSION

Vaping behavior changes across e-liquids and influences nicotine intake. Research is needed to understand the mechanisms that underlie these behavioral changes, including e-liquid pH and related sensory effects, subjective liking, and nicotine effects.

Characterization of puff topography of a prototype electronic cigarette in adult exclusive cigarette smokers and adult exclusive electronic cigarette users

Puff topography is an important measure of how consumers use e-vapor products. The purpose of this study was to evaluate the feasibility of using SODIM Smoking Puff Analyzer Mobile Device (SPA/M) to measure puff topography during use of a prototype e-cigarette (e-cig) in exclusive cigarette smokers (CS) and e-cig users (EC) under ad lib conditions in a clinic. Adult CS (n = 13) and EC (EC; n = 10) completed a 7-hr use session with the e-cig (2% tobacco-derived nicotine by weight, cartridge based system approximately the size of a king size cigarette). E-liquid usage was determined from cartridge weight. CS also smoked a single cigarette with the SPA/M. The SPA/M reliably recorded puff parameters throughout the study period, with CS puffs averaging 47.9 ± 18.2 ml volume, 2.3 ± 0.8 s duration, and 21.5 ± 4.6 ml/s flow rate. EC puffs averaged 53.4 ± 19.2 ml volume, 3.0 ± 1.3 s duration, and 19.6 ± 5.0 flow rate. CS average e-liquid use was 292 ± 214 mg and EC averaged 415 ± 305 mg over 7 h. When compared to a single use of their own brand cigarettes, CS took longer (2.3 ± 0.8 vs.1.7 ± 0.4 s) puffs with similar puff volume (47.9 ± 18.2 vs. 44.1 ± 10.5 ml) from the e-cig prototype. The puff duration, flow rate and peak flow were significantly lower (p < 0.05) with the e-cigs compared to cigarettes. Experienced EC and CS appeared to use the e-cig prototype differently, which is consistent with the literature. The SPA/M could be a useful tool in assessing e-cig use behavior for regulatory purposes.

Effect of e-liquid flavor on electronic cigarette topography and consumption behavior in a 2-week natural environment switching study

Electronic Nicotine Delivery Systems (ENDS) offer an alternate means to consume nicotine in a variety of flavored aerosols. Data are needed to better understand the impact of flavors on use behavior. A natural environment observational study was conducted on experienced ENDS users to measure the effect of e-liquid flavor on topography and consumption behavior. The RIT wPUMTM monitor was used to record to record the date and time and puff topography (flow rate, volume, duration) for every puff taken by N = 34 participants over the course of two weeks. All participants used tobacco flavor for one week, and either berry or menthol flavor for one week. Results provide strong evidence that flavor affects the topography behaviors of mean puff flow rate and mean puff volume, and there is insufficient evidence to support an influence of flavor on mean puff duration and mean puff interval. There was insufficient evidence, due to the low power associated with the limited number of observation days, to establish a relationship between flavor and cumulative consumption behavior. While the results indicate that an effect may be evident, additional observation days are required to establish significance.

Recommended core items to assess e-cigarette use in population-based surveys

A consistent approach using standardised items to assess e-cigarette use in both youth and adult populations will aid cross-survey and cross-national comparisons of the effect of e-cigarette (and tobacco) policies and improve our understanding of the population health impact of e-cigarette use. Focusing on adult behaviour, we propose a set of e-cigarette use items, discuss their utility and potential adaptation, and highlight e-cigarette constructs that researchers should avoid without further item development. Reliable and valid items will strengthen the emerging science and inform knowledge synthesis for policy-making. Building on informal discussions at a series of international meetings of 65 experts from 15 countries, the authors provide recommendations for assessing e-cigarette use behaviour, relative perceived harm, device type, presence of nicotine, flavours and reasons for use. We recommend items assessing eight core constructs: e-cigarette ever use, frequency of use and former daily use; relative perceived harm; device type; primary flavour preference; presence of nicotine; and primary reason for use. These items should be standardised or minimally adapted for the policy context and target population. Researchers should be prepared to update items as e-cigarette device characteristics change. A minimum set of e-cigarette items is proposed to encourage consensus around items to allow for cross-survey and cross-jurisdictional comparisons of e-cigarette use behaviour. These proposed items are a starting point. We recognise room for continued improvement, and welcome input from e-cigarette users and scientific colleagues.

Effects of six weeks of electronic cigarette use on smoking rate, CO, cigarette dependence, and motivation to quit smoking: A pilot study

OBJECTIVES

Switching from combustible tobacco cigarettes to electronic cigarettes (e-cigs) may or may not help smokers to reduce cigarette consumption and toxicant exposure. This pilot study investigated the effects of asking smokers to switch to e-cigs for 6weeks on smoking, exhaled carbon monoxide (CO) concentration, dependence, and motivation to quit smoking.

METHODS

Non-treatment seeking daily smokers (n=18) were given free e-cigs and instructed to use them instead of smoking cigarettes for 6weeks. Smokers were assessed at baseline, weekly for 6weeks, and at 8 and 10weeks for cigarettes/day, e-cig use, CO, cigarette dependence, and Contemplation Ladder.

RESULTS

All participants completed 6weeks; 17 completed 10weeks. At Week 6, cigarettes/day were reduced by two-thirds and CO by 45% from baseline (p's<.001), with reductions maintained at Week 10 (p's<.005). Cigarette dependence scores were a third lower at Weeks 6 (p<.002) and 10 (p<.001) than at baseline. Contemplation Ladder scores were higher at Weeks 6 and 10 (p's<.001) than at baseline. All these statistical effect sizes were large. At Week 6, number of reasons not to use e-cigs increased (p<.011).

CONCLUSIONS

Results show preliminary evidence for beneficial effects of short-term switching to e-cigs by non-treatment seeking smokers in terms of reduced smoke toxicant exposure and cigarette dependence, and increased motivation to quit, all maintained at least 4weeks after free e-cigs were no longer provided.

Differences in vaping topography in relation to adherence to exclusive electronic cigarette use in veterans

Background

Understanding vaping patterns of electronic cigarette (EC) use is important to understand the real-life exposure to EC vapor. Long term information on vaping topography in relation to tobacco cigarette (TC) smoking cessation success has not been explored.

Methods

Observational non-blinded study where active TC smokers were asked to replace TC with EC over 4 weeks (replacement phase, RP) followed by exclusive EC use for an additional 12 weeks (maintenance phase, MP). TC use and EC compliance was monitored weekly. Subjects were classified as success or failure whether or not they completed the protocol. Vaping information was stored and downloaded directly from the EC device and averaged per calendar day for analysis.

Results

From 25 subjects that followed the protocol, sixteen succeeded in completing the RP and 8 the MP (32%). No significant differences in baseline characteristics were noted between subjects in the success and failure groups including markers of nicotine addiction, plasma cotinine levels or smoking history. Success subjects showed significantly longer puff duration (seconds per vape) and total overall vapor exposure (number of vapes x average vape duration or vape-seconds) in both study phases. Furthermore, subjects in the success group continued to increase the number of vapes, device voltage and wattage significantly as they transitioned into the MP. After an initial drop, subjects in the success group were able to regain plasma cotinine levels comparable to their TC use while subjects in the failure group could not. Cotinine levels significantly correlated with the average number of daily vapes and vapes-seconds, but not with other vaping parameters.

Conclusion

The topography of smokers who adhere to exclusive EC use reflects a progressive and dynamic device adaptation over weeks to maintain baseline cotinine levels. The higher inhaled volume over time should be considered when addressing the potential toxic effects of EC and the variable EC adherence when addressing public health policies regarding their use.

Evaluation of e-liquid toxicity using an open-source high-throughput screening assay

The e-liquids used in electronic cigarettes (E-cigs) consist of propylene glycol (PG), vegetable glycerin (VG), nicotine, and chemical additives for flavoring. There are currently over 7,700 e-liquid flavors available, and while some have been tested for toxicity in the laboratory, most have not. Here, we developed a 3-phase, 384-well, plate-based, high-throughput screening (HTS) assay to rapidly triage and validate the toxicity of multiple e-liquids. Our data demonstrated that the PG/VG vehicle adversely affected cell viability and that a large number of e-liquids were more toxic than PG/VG. We also performed gas chromatography-mass spectrometry (GC-MS) analysis on all tested e-liquids. Subsequent nonmetric multidimensional scaling (NMDS) analysis revealed that e-liquids are an extremely heterogeneous group. Furthermore, these data indicated that (i) the more chemicals contained in an e-liquid, the more toxic it was likely to be and (ii) the presence of vanillin was associated with higher toxicity values. Further analysis of common constituents by electron ionization revealed that the concentration of cinnamaldehyde and vanillin, but not triacetin, correlated with toxicity. We have also developed a publicly available searchable website (www.eliquidinfo.org). Given the large numbers of available e-liquids, this website will serve as a resource to facilitate dissemination of this information. Our data suggest that an HTS approach to evaluate the toxicity of multiple e-liquids is feasible. Such an approach may serve as a roadmap to enable bodies such as the Food and Drug Administration (FDA) to better regulate e-liquid composition.

Use of Electronic Cigarettes Leads to Significant Beta2-Nicotinic Acetylcholine Receptor Occupancy: Evidence From a PET Imaging Study

Background

Electronic cigarettes (ECs) can influence nicotine addiction by delivering aerosolized nicotine. We investigated if nicotine from ECs is delivered to the brain β2*-nicotinic acetylcholine receptors (β2*-nAChR) and how this relates to the behavioral effects and nicotine delivery from cigarettes.

Methods

Seven nicotine users participated in positron emission tomography (PET) studies with (-)-[18F]Flubatine before and after nicotine challenge with 0, 8, and 36 mg/ml nicotine in a 3.3 Volt, 1.5 Ohm EC or a standard tobacco cigarette. Craving was evaluated before and after product use.

Results

Average β2*-nAChR occupancy was higher after 36 mg/ml EC challenge compared to 8 mg/ml EC at trend level. Average β2*-nAChR occupancy after tobacco cigarette smoking was 68 ± 18% and was not different compared with 8 mg/ml (64 ± 17%,) or 36 mg/ml (84 ± 3%) nicotine in EC users. Area under the curve (AUC) of blood nicotine level was higher in the cigarette smoking group compared with the 8mg/ml group (p = 0.03), but similar compared with the 36 mg/ml EC (p = 0.29). Drug craving was reduced after use of the tobacco cigarette, 8 mg/ml EC, and 36 mg/ml EC.

Conclusions

In this novel investigation of EC effects at β2*-nAChRs, we show that average β2*-nAChR occupancy was higher after 36 mg/ml EC challenge compared with 8 mg/ml EC. Receptor occupancy and arterial blood nicotine levels after cigarette smoking were similar to 36 mg/ml EC use under controlled conditions. These findings suggest that the ECs studied here have abuse liability and may provide an adequate alternative nicotine delivery system for cigarette smokers.

Implications

This is the first study to directly determine the neurologic effects of electronic cigarettes on human brain beta-2 nicotinic acetylcholine receptors using PET neuroimaging with (-)-[18F]Flubatine, a novel radiotracer. Our findings suggest that the e-cigarettes studied here have abuse liability and may provide an adequate alternative nicotine delivery system for cigarette smokers.

Adolescent brain cognitive development (ABCD) study: Overview of substance use assessment methods

One of the objectives of the Adolescent Brain Cognitive Development (ABCD) Study (https://abcdstudy.org/) is to establish a national longitudinal cohort of 9 and 10 year olds that will be followed for 10 years in order to prospectively study the risk and protective factors influencing substance use and its consequences, examine the impact of substance use on neurocognitive, health and psychosocial outcomes, and to understand the relationship between substance use and psychopathology. This article provides an overview of the ABCD Study Substance Use Workgroup, provides the goals for the workgroup, rationale for the substance use battery, and includes details on the substance use module methods and measurement tools used during baseline, 6-month and 1-year follow-up assessment time-points. Prospective, longitudinal assessment of these substance use domains over a period of ten years in a nationwide sample of youth presents an unprecedented opportunity to further understand the timing and interactive relationships between substance use and neurocognitive, health, and psychopathology outcomes in youth living in the United States.

In vitro RNA-seq-based toxicogenomics assessment shows reduced biological effect of tobacco heating products when compared to cigarette smoke

The battery of regulatory tests used to evaluate the risk of novel tobacco products such as heated tobacco products (THPs) presents some limitations including a bias towards the apical endpoint tested, and limited information on the mode of action. This is driving a paradigm shift to more holistic systems biology approaches. In this study, we used RNA-sequencing to compare the transcriptomic perturbations following acute exposure of a 3D airway tissue to the aerosols from two commercial THPs and a reference 3R4F cigarette. 2809 RNAs were differentially expressed for the 3R4F treatment and 115 and 2 RNAs for the two THPs (pFDR < 0.05, FC > 1.5), respectively. The relationship between the identified RNA features and gene ontologies were mapped showing a strong association with stress response, xenobiotics metabolism, and COPD-related terms for 3R4F. In contrast, fewer ontologies were found enriched for the THPs aerosols. "Response to wounding" was a common COPD-related term over-represented for the two THPs but at a reduced significance. Quantification of a cytokine panel post-exposure confirmed a pro-inflammatory effect of cigarette smoke but not for THPs. In conclusion, THPs have a reduced impact on gene expression compared to 3R4F.

Carbonyl Emissions in E-cigarette Aerosol: A Systematic Review and Methodological Considerations

Carbonyl emissions from tobacco cigarettes represent a substantial health risk contributing to smoking-related morbidity and mortality. As expected, this is an important research topic for tobacco harm reduction products, in an attempt to compare the relative risk of these products compared to tobacco cigarettes. In this study, a systematic review of the literature available on PubMed was performed analyzing the studies evaluating carbonyl emissions from e-cigarettes. A total of 32 studies were identified and presented. We identified a large diversity of methodologies, with substantial discrepancies in puffing patterns, aerosol collection and analytical methods as well as reported units of measurements. Such discrepancies make comparisons difficult, and in some cases the accuracy of the findings cannot be determined. Importantly, control for the generation of dry puffs was not performed in the vast majority of studies, particularly in studies using variable power devices, which could result in testing conditions and reported carbonyl levels that have no clinical relevance or context. Some studies have been replicated, verifying the presence of dry puff conditions. Whenever realistic use conditions were ensured, carbonyl emissions from e-cigarettes were substantially lower than tobacco cigarette smoke, while newer generation (bottom-coil, cotton wick) atomizers appeared to emit minimal levels of carbonyls with questionable clinical significance in terms of health risk. However, extremely high levels of carbonyl emissions were reported in some studies, and all these studies need to be replicated because of potentially important health implications.

Impact of E-cigarettes on Smoking and Related Outcomes in Veteran Smokers With Psychiatric Comorbidity

OBJECTIVE

Compared to the general U.S. population, smokers with comorbid psychiatric and/or substance use disorders have lower quit rates after evidence-based treatments and disproportionately high smoking-related deaths. Improved modalities for reducing tobacco-related harm in this subpopulation are needed. Because electronic cigarettes (e-cigarettes) can now deliver physiologically relevant levels of nicotine to consumers, they represent an additional nicotine delivery system that could be used in cessation interventions. While current data suggest that the use of e-cigarettes by smokers promotes a reduction in combustible cigarette use, smoking quit rates through use of e-cigarettes appears to be low. The goal of this study was to examine impact of e-cigarette use on combustible tobacco use as well as on the readiness to quit smoking and changes in nicotine dependence in a multimorbid population.

METHODS

We conducted a 4-week, open-label study in 43 military veteran smokers who had no immediate intention to stop smoking and were currently receiving psychiatric services from the Department of Veterans Affairs health care system. Participants were provided with a study e-cigarette they could use ad libitum along with other tobacco products and were encouraged to attend weekly laboratory visits and a one-month follow-up visit. Main outcome measures were number of cigarettes smoked per day (CPD), the frequency of e-cigarette use, the amount of money spent on combustible cigarettes (U.S. dollars/week), alveolar carbon monoxide (CO) levels, and urine cotinine levels.

RESULTS

Mean e-cigarette use was 5.7 days per week and only 9% of participants used the e-cigarette for fewer than 4 days per week. Significant reductions in breath CO (9.3 ppm to 7.3 ppm, p < .02) and CPD (from 16.6 to 5.7, p < .001) were observed across study weeks, and no serious adverse events were reported. Three participants (10% of completers) reported smoking cessation that was corroborated biochemically. At one-month follow-up, motivation to quit smoking remained significantly higher and the level of nicotine dependence was significantly lower than at baseline.

CONCLUSIONS

E-cigarettes are acceptable to smokers with psychiatric comorbidities, as indicated by sustained and frequent e-cigarette use by 90% of participants, and may promote reduction and/or cessation of combustible cigarette use. E-cigarettes appear to be a viable harm reduction modality in smokers with psychiatric comorbidities.

E-cigarettes: Impact of E-Liquid Components and Device Characteristics on Nicotine Exposure

BACKGROUND

Electronic cigarette (e-cigarette) use has increased substantially in recent years. While e-cigarettes have been proposed as a potentially effective smoking cessation tool, dualuse in smokers is common and e-cigarettes are widely used by non-smokers, including youth and young-adult non-smokers. Nicotine, the primary addictive component in cigarettes, is present at varying levels in many e-liquids. E-cigarettes may lead to initiation of nicotine use in adult and youth non-smokers, re-initiation of nicotine dependence in ex-smokers or increased severity of nicotine dependence in dual-users of cigarettes and e-cigarettes. As such, there are important clinical and policy implications to understanding factors impacting nicotine exposure from e-cigarettes. However, the broad and rapidly changing range of e-liquid constituents and e-cigarette hardware which could impact nicotine exposure presents a challenge. Recent changes in regulatory oversight of e-cigarettes underscore the importance of synthesizing current knowledge on common factors which may impact nicotine exposure.

METHODS

This review focuses on factors which may impact nicotine exposure by changing e-cigarette use behavior, puff topography, altering the nicotine yield (amount of nicotine exiting the e-cigarette mouth piece including nicotine exhaled as vapor) or more directly by altering nicotine absorption and bioavailability.

RESULTS

Topics reviewed include e-liquid components or characteristics including flavor additives (e.g., menthol), base e-liquid ingredients (propylene glycol, vegetable glycerin), components commonly used to dissolve flavorants (e.g., ethanol), and resulting properties of the e-liquid (e.g., pH), e-cigarette device characteristics (e.g., wattage, temperature, model) and user behavior (e.g., puff topography) which may impact nicotine exposure.

CONCLUSION

E-liquid characteristics and components, e-cigarette hardware and settings, and user behavior can all contribute substantially to nicotine exposure from e-cigarettes.

Associations of Electronic Cigarette Nicotine Concentration With Subsequent Cigarette Smoking and Vaping Levels in Adolescents

IMPORTANCE

Research indicates that electronic cigarette (e-cigarette) use (vaping) among adolescents is associated with the initiation and progression of combustible cigarette smoking. The reasons for this association are unknown.

OBJECTIVE

To evaluate whether use of e-cigarettes with higher nicotine concentrations is associated with subsequent increases in the frequency and intensity of combustible cigarette smoking and vaping.

DESIGN, SETTING, AND PARTICIPANTS

In this prospective cohort study involving students from 10 high schools in the Los Angeles, California, metropolitan area, surveys were administered during 10th grade in the spring (baseline) and 11th grade in the fall (6-month follow-up) of 2015 to students who reported using e-cigarettes within the past 30 days and the nicotine concentration level they used at baseline.

EXPOSURES

Self-report of baseline e-cigarette nicotine concentration of none (0 mg/mL), low (1-5 mg/mL), medium (6-17 mg/mL), or high (≥18 mg/mL) typically used during the past 30 days.

MAIN OUTCOMES AND MEASURES

Frequency of combustible cigarette smoking and e-cigarette use within the past 30 days (0 days [none], 1-2 days [infrequent], or ≥3 days [frequent]) and daily intensity of smoking and vaping (number of cigarettes smoked per day, number of vaping episodes per day, and number of puffs per vaping episode) at the 6-month follow-up.

RESULTS

The analytic sample included 181 students (96 boys [53.0%] and 85 girls [47.0%]; mean [SD] age, 16.1 [0.4] years). Each successive increase in nicotine concentration (none to low, low to medium, and medium to high) vaped was associated with a 2.26 (95% CI, 1.28-3.98) increase in the odds of frequent (vs no) smoking and a 1.65 (95% CI, 1.09-2.51) increase in the odds of frequent (vs no) vaping at follow-up after adjustment for baseline frequency of smoking and vaping and other relevant covariates. Use of e-cigarettes with high (vs no) nicotine concentration was associated with a greater number of cigarettes smoked per day at follow-up (adjusted rate ratio [RR], 7.03; 95% CI, 6.11-7.95). An association with a significantly greater number of vaping episodes per day was found with use of low (adjusted RR, 3.32; 95% CI, 2.61-4.03), medium (adjusted RR, 3.32; 95% CI, 2.54-4.10), and high (adjusted RR, 2.44; 95% CI, 1.63-3.24) nicotine concentrations (vs no nicotine) at baseline. Similar results were found for the number of puffs per vaping episode for low (adjusted RR, 2.05; 95% CI, 1.41-2.70), medium (adjusted RR, 3.39; 95% CI, 2.66-4.11), and high (adjusted RR, 2.23; 95% CI, 1.42-3.03) nicotine concentrations.

CONCLUSIONS AND RELEVANCE

The results of this study provide preliminary evidence that use of e-cigarettes with higher nicotine concentrations by youths may increase subsequent frequency and intensity of smoking and vaping.

E-cigarette Use and Cigarette Smoking Cessation among Texas College Students

OBJECTIVES

We examined the relationships between e-cigarette use and subsequent cigarette smoking behaviors at 6- and 12-month follow-ups among young adults.

METHODS

Participants were 18-29 year-old current and former cigarette smokers (N = 627) at 24 Texas colleges, participating in a 3-wave study. Multi-level, multivariable logistic regression models, accounting for school clustering, examined the impact of self-reported use of e-cigarettes on cigarette smoking status at 6- and 12-month follow-ups. Two mutually-exclusive groups of e-cigarette users were examined: those that used for cigarette smoking cessation and those that used for reasons other than cessation. Baseline covariates included socio-demographics, past quit attempts, nicotine dependence, cigarettes per day, and other tobacco use.

RESULTS

Use of e-cigarettes for cigarette smoking cessation was associated with increased odds of cigarette smoking cessation at 6- and 12-month follow-ups, while using e-cigarettes for other reasons was not, when adjusting for covariates.

CONCLUSIONS

Use of e-cigarettes for cigarette smoking cessation may reduce cigarette smoking rates in young adult college students. Additional research is needed examining e-cigarettes as a complement to evidence-based cessation resources that are associated with cigarette smoking cessation among young adults.

E-cigarettes in patients with COPD: current perspectives

Conventional cigarette smoking is known to result in significant COPD morbidity and mortality. Strategies to reduce and/or stop smoking in this highly vulnerable patient group are key public health priorities to reduce COPD morbidity and mortality. Unfortunately, smoking cessation efforts in patients with COPD are poor and there is a compelling need for more efficient approaches to cessation for patients with COPD. Electronic cigarettes (ECs) are devices that use batteries to vaporize nicotine. They may facilitate quit attempts and cessation in many smokers. Although they are not risk free, ECs are much less harmful than tobacco smoking. Hence, the use of ECs in vulnerable groups and in patients with challenges to abstain or multiple relapses to this habit may be promising. To date, little is known about health consequences of EC use among COPD smokers and whether their regular use has any effects on subjective and objective COPD outcomes. In the current review, we discuss the current perspectives and literature on the role of ECs in abstaining from conventional smoking and the effects of ECs on the respiratory tract in patients with COPD.

Electronic cigarette user plasma nicotine concentration, puff topography, heart rate, and subjective effects: Influence of liquid nicotine concentration and user experience

Electronic cigarette (ECIG) nicotine delivery and other effects may depend on liquid nicotine concentration and user experience. This study is the first to systematically examine the influence of ECIG liquid nicotine concentration and user experience on nicotine delivery, heart rate, puff topography, and subjective effects. Thirty-three ECIG-experienced individuals and 31 ECIG-naïve cigarette smokers completed 4 laboratory conditions consisting of 2, 10-puff bouts (30-sec interpuff interval) with a 3.3-V ECIG battery attached to a 1.5-Ω "cartomizer" (7.3 W) filled with 1 ml ECIG liquid. Conditions differed by liquid nicotine concentration: 0, 8, 18, or 36 mg/ml. Participants' plasma nicotine concentration was directly related to liquid nicotine concentration and dependent on user experience, with significantly higher mean plasma nicotine increases observed in ECIG-experienced individuals relative to ECIG-naïve smokers in each active nicotine condition. When using 36 mg/ml, mean plasma nicotine increase for ECIG-experienced individuals was 17.9 ng/ml (SD = 17.2) and 6.9 (SD = 7.1; p < .05) for ECIG-naïve individuals. Between-group differences were likely due to longer puffs taken by experienced ECIG users: collapsed across condition, mean puff duration was 5.6 sec (SD = 3.0) for ECIG-experienced and 2.9 (SD = 1.5) for ECIG-naïve individuals. ECIG use also suppressed nicotine/tobacco abstinence symptoms in both groups; the magnitude of abstinence symptom suppression depended on liquid nicotine concentration and user experience. These and other recent results suggest that policies intended to limit ECIG nicotine delivery will need to account for factors in addition to liquid nicotine concentration (e.g., device power and user behavior). (PsycINFO Database Record

Effect of Flavors and Modified Risk Messages on E-cigarette Abuse Liability

Objectives

To measure e-cigarettes' abuse liability compared to conventional tobacco cigarettes under flavor and message conditions amenable to regulation.

Methods

Two studies used 2×2 within-subjects designs with factors of e-cigarette flavor (Study 1: tobacco vs. menthol; Study 2: cherry vs. unflavored) and message (Study 1: reduced harm vs. no message; Study 2: reduced exposure to carcinogens vs. no message) with cigarette smokers (N(total) = 36). Linear mixed effects models assessed abuse liability for tobacco products. Outcomes included the price after which consumption is zero (the maximum amount participants would pay for a tobacco product) from the multiple choice procedure (MCP) and cigarette purchase task (CPT) and demand elasticity (price sensitivity) from the CPT.

Results

In the MCP, the price where consumption reached zero was significantly lower in all e-cigarette conditions except tobacco flavor (message or no message) compared to cigarettes (p < .05 each). Demand elasticity was significantly higher for menthol/no message and unflavored/reduced exposure message conditions relative to cigarettes (p < .05 each).

Conclusions

Flavors and modified risk messages included with e-cigarettes may affect e-cigarette abuse liability among smokers, suggesting regulatory pathways to influence demand for conventional and alternative tobacco products.

"Juice Monsters": Sub-Ohm Vaping and Toxic Volatile Aldehyde Emissions

An emerging category of electronic cigarettes (ECIGs) is sub-Ohm devices (SODs) that operate at ten or more times the power of conventional ECIGs. Because carcinogenic volatile aldehyde (VA) emissions increase sharply with power, SODs may expose users to greater VAs. In this study, we compared VA emissions from several SODs and found that across device, VAs and power were uncorrelated unless power was normalized by coil surface area. VA emissions and liquid consumed were correlated highly. Analyzed in light of EU regulations limiting ECIG liquid nicotine concentration, these findings suggest potential regulatory levers and pitfalls for protecting public health.

A critique of the US Surgeon General's conclusions regarding e-cigarette use among youth and young adults in the United States of America

BACKGROUND

In December 2016, the Surgeon General published a report that concluded e-cigarette use among youth and young adults is becoming a major public health concern in the United States of America.

METHODS

Re-analysis of key data sources on nicotine toxicity and prevalence of youth use of e-cigarettes cited in the Surgeon General report as the basis for its conclusions.

RESULTS

Multiple years of nationally representative surveys indicate the majority of e-cigarette use among US youth is either infrequent or experimental, and negligible among never-smoking youth. The majority of the very small proportion of US youth who use e-cigarettes on a regular basis, consume nicotine-free products. The sharpest declines in US youth smoking rates have occurred as e-cigarettes have become increasingly available. Most of the evidence presented in the Surgeon General's discussion of nicotine harm is not applicable to e-cigarette use, because it relies almost exclusively on exposure to nicotine in the cigarette smoke and not to nicotine present in e-cigarette aerosol emissions. Moreover, the referenced literature describes effects in adults, not youth, and in animal models that have little relevance to real-world e-cigarette use by youth. The Surgeon General's report is an excellent reference document for the adverse outcomes due to nicotine in combination with several other toxicants present in tobacco smoke, but fails to address the risks of nicotine decoupled from tobacco smoke constituents. The report exaggerates the toxicity of propylene glycol (PG) and vegetable glycerin (VG) by focusing on experimental conditions that do not reflect use in the real-world and provides little discussion of emerging evidence that e-cigarettes may significantly reduce harm to smokers who have completely switched.

CONCLUSIONS

The U.S. Surgeon General's claim that e-cigarette use among U.S. youth and young adults is an emerging public health concern does not appear to be supported by the best available evidence on the health risks of nicotine use and population survey data on prevalence of frequent e-cigarette use. Nonetheless, patterns of e-cigarettes use in youth must be constantly monitored for early detection of significant changes. The next US Surgeon General should consider the possibility that future generations of young Americans will be less likely to start smoking tobacco because of, not in spite of, the availability of e-cigarettes.

E-Liquid Autofluorescence can be used as a Marker of Vaping Deposition and Third-Hand Vape Exposure

In the past 5 years, e-cigarette use has been increasing rapidly, particularly in youth and young adults. Due to the novelty of e-cigarettes (e-cigs) and e-cigarette liquids (e-liquids), research on their chemo-physical properties is still in its infancy. Here, we describe a previously unknown and potentially useful property of e-liquids, namely their autofluorescence. We performed an emission scan at 9 excitation wavelengths common to fluorescent microscopy and found (i) that autofluorescence differs widely between e-liquids, (ii) that e-liquids are most fluorescent in the UV range (between 350 and 405 nm) and (iii) fluorescence intensity wanes as the emission wavelength increases. Furthermore, we used the autofluorescence of e-liquids as a marker for tracking e-cig aerosol deposition in the laboratory. Using linear regression analysis, we were able to quantify the deposition of a “vaped” e-liquid onto hard surfaces. Using this technique, we found that every 70 mL puff of an e-cigarette deposited 0.019% e-liquid (v/v) in a controlled environment. Finally, we vaped a surface in the laboratory and used our method to detect e-cig aerosol third-hand exposure. In conclusion, our data suggest that e-cigarette autofluorescence can be used as a marker of e-cigarette deposition.

Effects of nicotine versus placebo e-cigarette use on symptom relief during initial tobacco abstinence

Because electronic cigarettes (e-cigs) containing nicotine may relieve smoking abstinence symptoms similar to nicotine replacement therapy medication, we used within-subjects designs to test these effects with a first-generation e-cig in nonquitting and quitting smokers. In Study 1, 28 nontreatment-seeking smokers abstained overnight prior to each of 3 sessions. Minnesota Nicotine Withdrawal Scale (MNWS) withdrawal (and craving item) relief was assessed following 4 exposures (each 10 puffs) over 2 hr to e-cigs that either did (36 mg/ml) or did not (i.e., placebo, 0 mg/ml) contain nicotine or after no e-cig. Relief was greater after nicotine versus placebo e-cig (p < .05) but not after placebo versus no e-cig, showing relief was due to nicotine per se and not simple e-cig use behavior. Using a crossover design in Study 2, smokers preparing to quit soon engaged in 2 experimental 4-day quit periods on separate weeks. In weeks 1 and 3, all received a nicotine or placebo e-cig on Monday to use ad libitum while trying to abstain from smoking on Tuesday through Friday. (Week 2 involved resumption of ad libitum smoking.) MNWS and Questionnaire of Smoking Urges (QSU) craving were assessed at daily visits following 24-hr abstinence. Of 17 enrolled, 12 quit for ≥24 hr at least once, allowing test of relief because of e-cig use on quit days. Withdrawal and craving were reduced because of nicotine versus placebo e-cig use (both p < .05). In sum, compared with placebo e-cigs, nicotine e-cigs can relieve smoking abstinence symptoms, perhaps in a manner similar to Food and Drug Administration-approved nicotine replacement therapy products, although much more research with larger samples is needed. (PsycINFO Database Record

The association between electronic-cigarette use and self-reported oral symptoms including cracked or broken teeth and tongue and/or inside-cheek pain among adolescents: A cross-sectional study

Background

Little is known about oral health related to electronic-cigarette (EC) use, even though EC use is increasing rapidly. The aim of this study is to assess the relationship between EC use and oral health, including ‘gingival pain and/or bleeding’, ‘tongue and/or inside-cheek pain’, and ‘cracked or broken teeth’ among adolescents.

Methods

A total of 65,528 students in 2016 were included in this cross-sectional study.

Results

For EC use, 0.5% (n = 297) students were daily users, 1.9% (n = 1259) were ‘1 to 29 days past month users’, and 5.9% (n = 3848) were former users. Overall, 18.5% students reported they had experienced ‘gingival pain and/or bleeding’, 11.0% reported ‘tongue and/or inside-cheek pain’, and 11.4% reported a ‘cracked or broken tooth’ within the past 12 months. When comparing ‘daily EC users’, ‘1 to 29 days past month EC users’, and ‘former EC users’ with ‘never EC users’, the adjusted ORs for ‘cracked or broken tooth’ were 1.65 (95% CI: 1.19–2.27), 1.26 (95% CI: 1.06–1.51), and 1.16 (95% CI: 1.04–1.30), respectively. Comparing ‘daily EC users’ with ‘never EC users’, the adjusted OR for ‘tongue and/or inside-cheek pain’ was 1.54 (1.05–2.26). However, EC use among adolescents was not associated with ‘gingival pain and/or bleeding’ when adjusted for the potential confounders.

Conclusions

Based on the results, the odds of cracked or broken teeth among daily, ‘1 to 29 days past month’, and former EC users were significantly higher than those among never EC users. The odds of tongue and/or inside-cheek pain among daily EC users were significantly higher than those among never EC users. In conclusion, the results suggest that daily EC use among adolescents may be a risk factor for cracked or broken teeth and tongue and/or inside-cheek pain.

Reduced biological effect of e-cigarette aerosol compared to cigarette smoke evaluated in vitro using normalized nicotine dose and RNA-seq-based toxicogenomics

Electronic cigarettes (e-cigarettes) use has increased globally and could potentially offer a lower risk alternative to cigarette smoking. Here, we assessed the transcriptional response of a primary 3D airway model acutely exposed to e-cigarette aerosol and cigarette (3R4F) smoke. Aerosols were generated with standard intense smoking regimens with careful consideration for dose by normalizing the exposures to nicotine. Two e-cigarette aerosol dilutions were tested for equivalent and higher nicotine delivery compared to 3R4F. RNA was extracted at 24 hrs and 48 hrs post exposure for RNA-seq. 873 and 205 RNAs were differentially expressed for 3R4F smoke at 24 hrs and 48 hrs using a pFDR < 0.01 and a [fold change] > 2 threshold. 113 RNAs were differentially expressed at the highest dose of e-cigarette aerosol using a looser threshold of pFDR < 0.05, 3 RNAs exceeded a fold change of 2. Geneset enrichment analysis revealed a clear response from lung cancer, inflammation, and fibrosis associated genes after 3R4F smoke exposure. Metabolic/biosynthetic processes, extracellular membrane, apoptosis, and hypoxia were identified for e-cigarette exposures, albeit with a lower confidence score. Based on equivalent or higher nicotine delivery, an acute exposure to e-cigarette aerosol had a reduced impact on gene expression compared to 3R4F smoke exposure in vitro.

Subjective experiences at first use of cigarette, e-cigarettes, hookah, and cigar products among Texas adolescents

INTRODUCTION

Subjective experiences ("SEs") at first cigarette use have been thoroughly examined; however, limited research has examined SEs at first use of non-cigarette products. This study addresses this gap in the literature.

METHODS

Cross-sectional data from 6th, 8th and 10th grade students in four metropolitan areas of Texas (n=3907/N=461,069). Nausea, coughing, relaxation, rush/buzz, and dizziness at first use were assessed for cigarettes, e-cigarettes, hookah, and cigar products. Chi-square analyses examined differences in the prevalence of first use SEs by product. Weighted multiple logistic regression analyses examined the association of SEs and current product use. Covariates were grade, gender, race/ethnicity, and current other tobacco product use.

RESULTS

Exploratory factor analysis of SEs determined differing factor structures across tobacco products. For example, the following items loaded onto the positive SE factor: 1) relaxation, rush, and dizziness for cigarettes, and 2) relaxation and rush for e-cigarettes, hookah, and cigar products. Prevalence of negative SEs (coughing and nausea) were higher for cigarette and cigar products compared to e-cigarettes and hookah. Positive SEs for cigarettes were associated with increased odds of current cigarette use (AOR=1.51); similarly positive SEs for cigars were associated with increased odds of current cigar use (AOR=2.11). Feeling nauseous at first use of cigars was associated with decreased odds of current cigar use (AOR=0.18). No SEs were associated with current e-cigarette or hookah use.

CONCLUSIONS

Subjective experiences at first use differ by tobacco product. Longitudinal studies are needed to examine temporal relationships between SEs at first use and sustained tobacco use.

The Influence of a Mouthpiece-Based Topography Measurement Device on Electronic Cigarette User's Plasma Nicotine Concentration, Heart Rate, and Subjective Effects Under Directed and Ad Libitum Use Conditions

INTRODUCTION

Electronic cigarettes e-cigarettes aerosolize a liquid solution often containing nicotine. e-cigarette nicotine delivery may be influenced by user puffing behaviors ("puff topography"). E-cigarette puff topography can be recorded using mouthpiece-based computerized systems. The present study sought to examine the extent to which these systems influence e-cigarette nicotine delivery and other e-cigarette associated acute effects under ad libitum use conditions.

METHODS

Plasma nicotine concentration, heart rate, and subjective effects were assessed in 29 experienced e-cigarette users using their preferred e-cigarette battery and liquid (≥12mg/mL nicotine) in two sessions differing only by the presence of a mouthpiece-based device. In both sessions, participants completed a directed e-cigarette use bout (10 puffs, 30-s interpuff interval) and a 90-min ad libitum bout. Puff topography was recorded in the session with the topography mouthpiece.

RESULTS

Plasma nicotine, heart rate, and subjective effects, aside from "Did the e-cigarette Taste Good?" were independent of topography measurement (higher mean taste ratings were observed in the no topography condition). Mean (SEM) plasma nicotine concentration following the ad libitum bout was 34.3ng/mL (4.9) in the no topography condition and 35.7ng/mL (4.3) in the topography condition. Longer puff durations, longer interpuff intervals, and larger puff volumes were observed in the ad libitum relative to the directed bout.

CONCLUSIONS

E-cigarette use significantly increased plasma nicotine concentration and heart rate while suppressing abstinence symptoms. These effects did not differ when a topography mouthpiece was present. Future studies using ad libitum e-cigarette use bouts would facilitate understanding of e-cigarette toxicant yield.

IMPLICATIONS

No prior study has examined whether mouthpiece-based topography recording devices influence e-cigarette associated nicotine delivery, heart rate, or subjective effects under ad libitum conditions or assessed ad libitum puff topography in experienced individuals using their preferred e-cigarette battery and liquid with a mouthpiece-based computerized device. E-cigarette use significantly increased plasma nicotine concentration and heart rate while suppressing abstinence symptoms. These effects did not differ when a topography mouthpiece was present. Ad libitum puff topography differed from puff topography recorded during directed puffing. These findings suggest that future studies using ad libitum use bouts would facilitate better understanding of e-cigarette toxicant yield.

Delivery of nicotine aerosol to mice via a modified electronic cigarette device

BACKGROUND

Although both men and women use e-cigarettes, most preclinical nicotine research has focused on its effects in male rodents following injection. The goals of the present study were to develop an effective e-cigarette nicotine delivery system, to compare results to those obtained after subcutaneous (s.c.) injection, and to examine sex differences in the model.

METHODS

Hypothermia and locomotor suppression were assessed following aerosol exposure or s.c. injection with nicotine in female and male mice. Subsequently, plasma and brain concentrations of nicotine and cotinine were measured.

RESULTS

Passive exposure to nicotine aerosol produced concentration-dependent and mecamylamine reversible hypothermic and locomotor suppressant effects in female and male mice, as did s.c. nicotine injection. In plasma and brain, nicotine and cotinine concentrations showed dose/concentration-dependent increases in both sexes following each route of administration. Sex differences in nicotine-induced hypothermia were dependent upon route of administration, with females showing greater hypothermia following aerosol exposure and males showing greater hypothermia following injection. In contrast, when they occurred, sex differences in nicotine and cotinine levels in brain and plasma consistently showed greater concentrations in females than males, regardless of route of administration.

DISCUSSION

In summary, the e-cigarette exposure device described herein was used successfully to deliver pharmacologically active doses of nicotine to female and male mice. Further, plasma nicotine concentrations following exposure were similar to those after s.c. injection with nicotine and within the range observed in human smokers. Future research on vaped products can be strengthened by inclusion of translationally relevant routes of administration.

The Importance of Conditioned Stimuli in Cigarette and E-Cigarette Craving Reduction by E-Cigarettes

This study examined the impact of four variables pertaining to the use of e-cigarettes (e-cigs) on cravings for tobacco cigarettes and for e-cigs after an overnight abstinence period. The four variables were the nicotine level, the sensorimotor component, the visual aspect, and the aroma of the e-cig. In an experimental study, 81 participants without prior vaping experience first got acquainted with using e-cigs in a one-week tryout period, after which they participated in a lab session assessing the effect of five minutes of vaping following an abstinence period of 12 h. A mixed-effects model clearly showed the importance of nicotine in craving reduction. However, also non-nicotine factors, in particular the sensorimotor component, were shown to contribute to craving reduction. Handling cues interacted with the level (presence/absence) of nicotine: it was only when the standard hand-to-mouth action cues were omitted that the craving reducing effects of nicotine were observed. Effects of aroma or visual cues were not observed, or weak and difficult to interpret, respectively.