Nicotine matters in predicting subsequent smoking after e-cigarette experimentation: A longitudinal study among Finnish adolescents

Sex differences in nicotine intake and relapse behavior in nicotine-dependent adult wistar rats

Introduction

Tobacco use is highly addictive and the leading cause of premature mortality in the world. Long-access nicotine self-administration procedures in rats closely model human smoking behavior. However, significant gaps remain in our understanding of sex differences in the development of dependence and relapse in adult rats.

Methods

In the present study, we investigated operant responding for both nicotine and saline and the development of dependence in adult rats of both sexes. The rats had daily access to nicotine or saline for 6 h per day, 7 days per week. Dependence was assessed by evaluating precipitated and spontaneous somatic withdrawal signs, measuring locomotor activity in the small open field test, and assessing anxiety-like behavior in the large open field and elevated plus maze test. The sucrose preference test was used to determine if cessation of nicotine intake leads to anhedonia. It was also investigated if a period of forced abstinence affects nicotine-seeking behavior.

Results

This study showed that nicotine intake is higher in females than in males when given daily long access to nicotine. Daily nicotine self-administration led to more precipitated and spontaneous somatic withdrawal signs compared to saline self-administration, with no sex differences observed. In addition, cessation of nicotine intake led to a similar increase in activity in both males and females in the small open field test. However, cessation of nicotine intake did not increase anxiety-like behavior or cause anhedonia in either males or females. A time course analysis revealed that the nicotinic acetylcholine receptor antagonist mecamylamine affected nicotine intake differently in males and females, increasing intake in males and decreasing intake in females. Three weeks of forced abstinence led to an increase in nicotine and saline-seeking behavior. The rats exhibited more nicotine than saline seeking, and the females displayed more nicotine seeking than the males.

Discussion

The present findings demonstrate that females self-administer more nicotine and display more nicotine-seeking behavior than males. Furthermore, there were no sex differences in somatic withdrawal signs or activity during abstinence from nicotine. This work underscores the importance of considering sex differences across various aspects of addiction, including intake and relapse, when developing novel treatments for tobacco use disorder.

The Effect of New Trend Electronic Cigarettes on Dental Caries in Relation to Glucosyltransferase B and Secretory Immunoglobulin A (A Case-control Study)

Electronic cigarettes (vapes) are actively used, and their use is growing globally, especially among young people. Its spread is rapid due to the presence of unproven rumors that it is used to treat smoking addiction as it aids in smoking cessation. However, E.C has a negative impact on dental health by affecting the oral microbiome and salivary components. The goal of this study was to evaluate the impact of electronic cigarettes on dental caries in relation to glucosyltransferase B and secretory immunoglobulin in the saliva of electronic cigarette users. Ninety active males were divided into two groups: 45 electronic-cigarette smokers in addition to 45 non-electronic-cigarette smokers as a control group. An oral examination was performed on the studied groups, and decayed missing filling tooth surfaces (DMFS) were documented. Additionally, unstimulated saliva was collected to evaluate salivary glucosyltransferase B and secretory immunoglobulin A by using a sandwich enzyme-linked immune-sorbent assay (ELISA). The obtained outcomes showed that decayed, missing, and filled Surfaces values(DMFS), salivary glucosyltransferase B, and salivary secretory immunoglobulin A were greater in the study group than in control group. Additionally, a correlation between glucosyltransferase B, secretory immunoglobulin A, and DMFS was positive and significant. It was concluded that e-cigarettes may have an effect on saliva components and dental caries.

Association of Electronic Cigarette Usage with the Subsequent Initiation of Combustible Cigarette Smoking among Dental Students in Riyadh, Saudi Arabia: A Longitudinal Study

The use of electronic cigarettes, or "e-cigarettes", among youths has sparked worries about the possibility of nicotine dependence as a serious public health issue. Dental practitioners play a critical role in helping their patients quit smoking. Dental schools across the globe have policies encouraging their students to help patients quit smoking. Current research, however, indicates that a significant portion of dental students smoke combustible cigarettes and use e-cigarettes. According to studies, using e-cigarettes has resulted in the subsequent initiation of combustible cigarette smoking among its users. The aim of this study was to determine the association between the use of electronic cigarettes and the subsequent initiation of combustible cigarette smoking among dental students who were not attitudinally susceptible to smoking combustible cigarettes. A longitudinal cohort study was conducted among 121 study participants who were never combustible cigarette users and were attitudinally non-susceptible to smoking at baseline. At baseline, 66 (54.6%) study participants were categorized as e-cigarette users who were attitudinally non-susceptible to combustible cigarette smoking, and 55 (45.4%) study participants were categorized as non-users who were attitudinally non-susceptible to combustible cigarette smoking. The initiation of combustible cigarette smoking was assessed at 6- and 12-month intervals. Binomial regression analysis of the outcome at the end of one-year follow-up, when analyzed with independent variables, revealed a significant influence of e-cigarette use on taking up combustible cigarette smoking [Relative Risk: 9.395; 95% CI: 3.03-29.04]. Chi-squared analysis of independent variables revealed e-cigarette use to be significantly associated with fathers' education level (p = 0.00), parental cigarette smoking status (p = 0.00), cigarette smoking among friends (p = 0.00), and family income (p = 0.00). E-cigarette users are more likely to believe it to be healthier (p = 0.00) than combustible smoking. In the present study, e-cigarette usage demonstrated a significant influence on taking up combustible cigarette smoking among its users. Educational institutions should implement stringent policies and regulations to prevent health professionals from using these products.

Longitudinal bidirectional association between youth electronic cigarette use and tobacco cigarette smoking initiation in Thailand

INTRODUCTION

This study quantifies the longitudinal association between e-cigarette use and subsequent conventional cigarette initiation and vice versa among Thai youths.

METHODS

Data from a longitudinal survey of 6045 Thai seventh grade students with baseline in 2019 and the 12-month follow-up in 2020 were analysed using complex survey multivariate logistic regressions to assess whether e-cigarette use was associated with subsequent cigarette smoking (ever, current and dual product users at follow-up) among baseline never smokers.

RESULTS

Consistent with prior findings from other countries, among those who had never smoked cigarettes at baseline, ever e-cigarette users were more likely to try cigarette smoking (adjusted OR 4.44; 95% CI 2.23 to 8.86; p<0.001), or become dual users (adjusted OR 5.31; 95% CI 2.63 to 10.74; p<0.001) 1 year later. Baseline current e-cigarette users were more likely to become ever smokers (adjusted OR 5.37; 95% CI 1.82 to 15.90; p=0.005), current smokers (OR 3.92; 95% CI 1.69 to 9.14; p=0.003) and dual product users (adjusted OR 6.96; 95% CI 1.54 to 31.38; p=0.015) at the 12-month follow-up than non-e-cigarette users. Similarly, among never e-cigarette users at baseline, ever cigarette smoking were more likely to try e-cigarettes (adjusted OR 3.38; 95% CI 1.66 to 6.88; p=0.002), currently use e-cigarettes (adjusted OR 2.75; 95% CI 1.47 to 5.13; p=0.003) and currently use both e-cigarettes and cigarettes (adjusted OR 4.87; 95% CI 2.92 to 8.13; p<0.001) at the follow-up than never smokers. Among never e-cigarette users at baseline, current-cigarette smoking were more likely to try e-cigarettes (adjusted OR 6.21; 95% CI 2.58 to 14.95; p<0.001), currently use e-cigarettes (adjusted OR 2.80; 95% CI 1.27 to 6.14; p=0.014) and currently use both e-cigarettes and cigarettes (adjusted OR 7.70; 95% CI 3.45 to 17.19; p<0.001) at the follow-up than never smokers.

CONCLUSIONS

This longitudinal study in Asian low-income and middle-income countries supports the prospective association of youth e-cigarette use with subsequent smoking initiation and youth cigarette use with subsequent e-cigarette initiation that is similar to that observed in high-income Western countries.

Association between e-cigarette use and susceptibility to tobacco product use: findings from the 2019 China National Youth Tobacco Survey

Background

There is an ongoing debate about whether e-cigarettes act as a gateway to tobacco smoking or contribute to smoking cessation, and relevant studies are limited among Chinese adolescents. This cross-sectional study therefore aimed to explore the relationship between e-cigarette use and susceptibility to tobacco product use among Chinese high school students.

Methods

The study population comprised 107,633 never smokers and 19,377 former smokers, generated from the 2019 China National Youth Tobacco Survey. The primary independent variables of interest were ever e-cigarette use, current e-cigarette use, and the frequency of current e-cigarette use. The main outcome was the susceptibility to tobacco product use. Multilevel logistic regression was used to estimate the association between the primary independent variables of interest and the outcome variable. Moreover, two additional multilevel logistic regression models were fitted using two alternative definitions of the outcome as the sensitivity analyses.

Results

Among never smokers, students who ever used e-cigarettes were more likely to be susceptible to tobacco product use compared to students who never used e-cigarettes (AOR = 2.83, 95%CI = 2.59-3.08). Students who currently used e-cigarettes were more likely to be susceptible to tobacco product use than those who did not currently use e-cigarettes (AOR = 3.89, 95%CI = 3.21-4.72). Among former smokers, with the same settings of modeling, the AORs were 1.76 (95%CI = 1.62-1.91) and 3.16 (95%CI = 2.52-3.97), respectively. Similar results were obtained from the two sensitivity analyses.

Conclusion

Among Chinese high school students, both never smokers and former smokers, e-cigarette use, especially current e-cigarette use, was positively associated with susceptibility to tobacco product use. It is recommended to strengthen the monitoring of e-cigarettes and to provide targeted health education to adolescents.

Experiences and Perceptions of E-Cigarette Cessation for Young Adults in Rural Communities

BACKGROUND

Electronic nicotine delivery systems (ENDS), also known as e-cigarettes, are the most commonly used tobacco products among young adults in the United States. Young adults in rural areas have a higher prevalence of ENDS use compared to their urban counterparts, yet there is limited evidence regarding the in-depth understanding of experiences and perspectives directly from young adults.

OBJECTIVES

The aim of this study was to explore individual experiences and perspectives about use and cessation of ENDS from young adults in rural areas.

METHODS

This was a qualitative study using interpretive description for analysis. Young adults (18-24 years) who used ENDS every day but not other tobacco products (cigarettes, smokeless, etc.) in the past month and had an address in a rural county of Wisconsin were eligible; there were nine participants interviewed using Zoom. Interview questions focused on initial use, maintenance of use, experiences of quitting, and social and rural environmental contexts regarding ENDS.

RESULTS

Three themes emerged with eight categories: (a) addiction to ENDS and health, (b) cessation and resources, and (c) rural environment and culture in ENDS addiction.

DISCUSSION

Findings have implications for ENDS cessation interventions targeting young adults in rural areas.

Recruitment of Young Adults: Lessons Learned From Research on Rural E-Cigarette Use and Cessation

Electronic nicotine delivery system (ENDS) use continues to grow in rural areas of the United States. In particular, young adults (18-24 years) in rural areas are a hard-to-reach population in regard to understanding the growing ENDS use trend. The purpose of this article was to describe recruitment strategies that were used for a series of ENDS-relevant projects for young adults in rural areas, report recruitment yields from these strategies, and provide methodological considerations to aid researchers in improving recruitment. We used descriptive statistical methods to characterize recruitment yields (responses to screening vs initial invites, and number of individuals who fully met eligibility criteria vs responses to screening) from 2 ENDS studies that focused on 3 main recruitment strategies, including student directories, leadership offices (eg, Student Affairs), and regional tobacco control support networks (eg, Area Health Education Centers) for reaching young adults in rural communities. The recruitment yield rates varied and ranged from 2% to 14% depending on strategy with leadership offices resulting in the highest recruitment yield. Methodological considerations by strategy are described in detail. Results of this study can be used to inform tailored recruitment strategies to increase the representation of rural young adults in ENDS or other tobacco research.

Systematic Review and Critical Analysis of Longitudinal Studies Assessing Effect of E-Cigarettes on Cigarette Initiation among Adolescent Never-Smokers

Prospective longitudinal studies mainly conclude on a causal role of e-cigarettes in the initiation of cigarettes in flagrant contradiction with conclusions drawn from epidemiology and other studies showing a sharp decline in cigarette use in parallel with the spread of e-cigarette use. This systematic review explores the reasons for this discrepancy.

METHODS

Among 84 publications on e-cigarette/cigarette association in adolescents identified in the Medline database from 2011 to 2022, 23 concern 22 never-smoker longitudinal sub-cohorts.

RESULTS

A link between e-cigarette experimentation at T1 and cigarette initiation at T2 is reported in sub-cohort analyses of never-smokers (AOR: 1.41 to 8.30). However, studies exclude 64.3% of T1 e-cigarette experimenters (because of dual-use) and 74.1% of T2 cigarette experimenters. With this study design, e-cigarettes contribute only to 5.3% of T2 cigarette experimentation, casting major doubt on the external validity of results and authors' conclusions that e-cigarettes have a significant effect on the initiation of cigarettes (Gateway effect) at the population level. This sub-cohort design prohibits highlighting any Diversion effect, which is the most likely mechanism accounting for the competition between these two products.

CONCLUSIONS

While nicotine abstinence remains the best medical option, over-regulation of e-cigarettes because of misinterpretation of longitudinal study results may be detrimental to public health and tobacco control.

Consequences of adolescent drug use

Substance use in adolescence is a known risk factor for the development of neuropsychiatric and substance use disorders in adulthood. This is in part due to the fact that critical aspects of brain development occur during adolescence, which can be altered by drug use. Despite concerted efforts to educate youth about the potential negative consequences of substance use, initiation remains common amongst adolescents world-wide. Additionally, though there has been substantial research on the topic, many questions remain about the predictors and the consequences of adolescent drug use. In the following review, we will highlight some of the most recent literature on the neurobiological and behavioral effects of adolescent drug use in rodents, non-human primates, and humans, with a specific focus on alcohol, cannabis, nicotine, and the interactions between these substances. Overall, consumption of these substances during adolescence can produce long-lasting changes across a variety of structures and networks which can have enduring effects on behavior, emotion, and cognition.

Regional French evolution of tobacco and e-cigarette experimentation and use among adolescents aged 15-16 years: A cross-sectional observational study conducted in the Loire department from 2018 to 2020

Background

We assessed/compared the evolution of tobacco and e-cigarette experimentation and use among French adolescents of the Loire department aged 15-16 years.

Methods

A descriptive, cross-sectional/observational study conducted in 2018-2020 among 7,950 Year 11 pupils attending 27 public secondary schools of the Loire department, France.

Results

From 2018 to 2020, 66.18% of adolescents were "non-vapers and non-smokers", 19.76% were "vapers and smokers", 7.90% were "non-vapers and smokers" and 6.15% were "vapers and non-smokers". E-cigarette experimentation was more prevalent than tobacco experimentation (44.92% vs 41.67%), and daily vaping was less prevalent than daily smoking (5.40% vs 10.24%). More boys than girls were daily vapers or daily smokers. A decrease was observed in tobacco experimentation (from 41.22% in 2018 to 39.73% in 2020) and e-cigarette experimentation (from 50.28% in 2018 to 41.25% in 2020). Current vaping remained stable, with an increase in daily vaping. French adolescent vapers frequently use e-liquids with little or no nicotine or with fruit or sweet flavours.

Conclusions

Adolescents used e-cigarettes mainly for experimental and/or recreational purposes, with no intention of progression to daily smoking. Although the design of this study is not longitudinal and caution must be exercised, from our cross-sectional observational study data, it appears that the proportion of "non-vapers and non-smokers" tended to increase. "Smokers" tended to progress to the dual use of vaping and smoked tobacco, with the likely intention to reduce or quit smoking.

Nicotine flux as a powerful tool for regulating nicotine delivery from e-cigarettes: Protocol of two complimentary randomized crossover clinical trials

INTRODUCTION

Electronic cigarette (EC) use has increased rapidly in the last decade, especially among youth. Regulating nicotine delivery from ECs could help curb youth uptake and leverage EC use in harm reduction yet is complicated by varying device and liquid variables that affect nicotine delivery. Nicotine flux, the nicotine emission rate, is a parameter that incorporates these variables and focuses on the performance rather than the design of an EC. Nicotine flux therefore could be a powerful regulatory tool if it is shown empirically to predict nicotine delivery and subjective effects related to dependence.

METHODS AND ANALYSIS

This project consists of two complementary clinical trials. In Trial I, we will examine the relationship between nicotine flux and the rate and dose of nicotine delivery from ECs, hence, impacting abuse liability. It will also examine the extent to which this relationship is mediated by nicotine form (i.e., freebase versus protonated). At Yale School of Medicine (YSM), study participants will puff EC devices under conditions that differ by flux and form, while arterial blood is sampled in high time resolution. In Trial II, we will assess the relationship between nicotine flux, form, and subjective effects. At the American University of Beirut (AUB), participants will use EC devices with varying nicotine fluxes and forms, while dependency measures, such as the urge to use ECs, nicotine craving, and withdrawal symptoms, will be assessed. We will also monitor puffing intensity and real-time exposure to toxicants.

ETHICS AND DISSEMINATION

The protocol of Trial I and Trial II was approved by YSM and AUB IRBs, respectively. We will disseminate study results through peer-reviewed publications and conference presentations.

TRIAL REGISTRATION

NCT05706701 for Trial I and NCT05430334 for Trial II.

Knowledge, Attitudes and Behaviours of Adolescents and Young Adult Population on the Use of E-Cigarettes or Personal Vaporizer

The use of electronic cigarettes (e-cig) or personal vaporizers (PV) has increased in recent years, especially among adolescents and adults, increasing risk factors for their health or being a starting point for other risk behaviours. The aim of our study is to learn the knowledge, attitudes and behaviours of the adolescent and young adult population on the use of e-cigarettes or PVs. A cross-sectional descriptive study was carried out among 375 subjects. The use of e-cigs or PVs was measured using a self-administered questionnaire. Overall, 13.33% of the respondents used e-cigarettes or PVs. A correlation could be established between vape use and age, with 14-18-year-olds being the highest users (25.9%). Additionally, 90.13% of the respondents answered that e-cig or PV use was harmful to health. Other behaviours, such as consumption of energy drinks (ED), increases the probability of vaping by 3.08 times (CI = 1.55-6.29; p = 0.001). Subjects aged 23-26 years and 27-34 years are less likely to vape than subjects aged 14-18 years (OR = 0.31: CI = 0.09-0.96; p = 0.044; OR = 0.07: CI = 0.00-0.63; p = 0.037). The same applies to subjects with secondary education (OR = 0.17: CI = 0.04-0.66; p = 0.011) and postgraduate education (OR = 0.07: CI = 0.06-1.19; p = 0.043), than subjects with primary education. The use of e-cigs and PVs starts at an early age, despite the known harmful effects of e-cigs and PVs. Their use may occur mainly in recreational situations and in association with other substances such as ED.

E-cigarette use in global digital youth culture. A qualitative study of the social practices and meaning of vaping among 15-20-year-olds in Denmark, Finland, and Norway

BACKGROUND

The introduction of e-cigarettes on the tobacco market has brought new regulatory challenges, and particular concerns relate to e-cigarette uptake among young people. The aim of this study was to explore the use and social meaning of e-cigarettes among Nordic young people and to discuss this in the context of current legislation.

METHODS

Thirteen focus groups were conducted with 46 Danish, Finnish, and Norwegian young people (24 boys) with vaping experience aged 15-20 years (mean age 17 years).

RESULTS

Young people's vaping stood out as an inherently social practice that was commonly interlinked with experimental use patterns. Relative to smoking, vaping was seen as socially acceptable and less harmful to health. Product innovations like flavour additives and nicotine-free liquid options added to perceptions of low harm, and innovative device design features facilitated new and playful user practices. Finally, digital markets eased the young people's access to e-cigarettes, and the digital world also represented an arena for e-cigarette exposure and self-presentation. They commonly viewed vaping-related content in their social media feeds and also produced such content themselves.

CONCLUSION

Young people's vaping is a social practice interwoven in contemporary digital and global youth culture. Transnational regulations are needed to support individual countries in preventing e-cigarette use and exposure among young people.

The Influence of COVID-19 Pandemic on the Frequent Use of E-Cigarettes and Its Association with Substance Use and Mental Health Symptoms

BACKGROUND

Although several studies examined the association between e-cigarettes, substance use, and mental health conditions, there is limited research on whether COVID-19-related stress and health outcomes, mental health symptoms, and substance use differ by the frequency of e-cigarette use during the COVID-19 pandemic. We assessed the association of past 30-day frequent use of e-cigarettes with alcohol, cannabis, anxiety/depression, and COVID-19 impact.

METHODS

We conducted a national online cross-sectional survey among a random sample of US adults aged 18 years or older (N = 5065) between 13 May 2021, and 9 January 2022. A multinomial logistic regression analysis was performed to assess the study aims.

RESULTS

Of the participants, 7.17% reported once to several times per month (OSTPM), 6.95% reported once to several times per week (OSTPW), and 6.57% reported every day to several times per day (ESTPD) use of e-cigarettes in the past month. Alcohol and cannabis use ESTPD and once to several times per week/month (OSTPW/M) were associated with a higher likelihood of e-cigarette use ESTPD and OSTPW/M, respectively. Anxiety/depression was associated with e-cigarette use ESTPD and OSTPW. Individuals who considered social distancing to be stressful were more likely to use e-cigarettes ESTPD and OSTPW/M compared to those that considered social distancing as not stressful.

CONCLUSION

Individuals who engaged in the frequent use of alcohol or cannabis, had depression/anxiety, and considered social distancing to be stressful were more likely to engage in frequent e-cigarette use. Improving efforts geared toward reducing the use of substances may help decrease the health risks associated with e-cigarette use.

Opinions and Practices Regarding Electronic Cigarette Use among Middle School Students from Rural Areas of Romania

Background: The objectives of the study were to assess awareness, opinions, and practices regarding electronic cigarette (e-cigarette) use, as well as factors associated with their use, among middle-school aged students from rural areas of Romania. Methods: The study sample included 748 middle-school students aged 13–14 years from 24 schools from rural areas situated in two counties from Romania, after receiving parental consent. A cross-sectional study using confidential questionnaires which assessed smoking-related behaviors, and also opinions and practices related to e-cigarettes use, was performed in 2019 among the participating middle-schoolers. Results: 96.3% of the middle schoolers have heard about e-cigarettes. A percentage of 72.7% of the smokers, 50.8% of the ex-smokers, and 15.4% of the non-smokers had tried e-cigarettes at least once in their life; 20.3% of the smokers, 4.8% of the ex-smokers, and 4.5% of the non-smokers reported using e-cigarettes in the last month. The results of multivariate logistic regression analysis pointed out that e-cigarette use at least once during lifetime was associated with having friends who tried e-cigarettes, having stronger beliefs that they can help quit smoking and that they are less dangerous than traditional cigarettes. The intention to use e-cigarettes in the next year and smoking behavior were also correlated with e-cigarettes experimentation, while no gender differences were found. Conclusions: The results underline the importance of having prevention programs and interventions concerning e-cigarettes consumption, since e-cigarettes consumption is spread among Romanian adolescents from rural areas.

Smoking Susceptibility in Canadian Adolescent Electronic-Cigarette Users

Background: E-cigarette use is increasing among Canadian youth, with experimentation especially prevalent among never-smoking youth. Among this group, there is concern e-cigarette use contributes to future initiation of smoking through a gateway effect. However, e-cigarette use and smoking share many common risk factors; a postulated mechanism to explain the apparent causal pathway from e-cigarette use to smoking initiation in previously smoking-naïve youth. A better understanding of the relationships between smoking susceptibility and e-cigarette use among never-smoking youth is needed. Purpose/objectives: The primary aim of this study was to gain a deeper understanding of the risk factors associated with smoking susceptibility in youth who have recently used e-cigarettes. Methods: This study used data (n = 40,363) from the 2018/2019 Canadian Student Tobacco Alcohol and Drug Use Survey (CSTADS) to compare the risk factor profiles of susceptible and non-susceptible never-smoking e-cigarette users, as well as susceptible and non-susceptible never-smoking youth who have never used an e-cigarette. Results: E-cigarette use, independent of susceptibility status, was associated with a sociodemographic and behavioral risk factor profile likely to confer a higher risk of initiating smoking. Among e-cigarette users, smoking susceptibility was associated with more smoking risk factors. Conclusions/importance: Study findings support a common risk-factor model, rather than e-cigarette use itself, to explain differences in the likelihood of smoking initiation among e-cigarette users. E-cigarette use and smoking initiation may be interchangeable outcomes amongst those with smoking risk factors. The risks of e-cigarette use, and their regulatory status, need to be balanced with their potential as harm reduction tools.

Dual use of e-cigarettes with conventional tobacco is associated with increased sleep latency in cross-sectional Study

The health effects of e-cigarettes remain relatively unknown, including their impact on sleep quality. We previously showed in a pilot study that females who smoke both conventional tobacco and vape e-cigarettes (dual users) had decreased sleep quality (measurement of how well an individual is sleeping) and increased sleep latency (amount of time to fall asleep), suggesting an influence by gender. Cough is also known to adversely impact sleep quality and may be caused by inhalant use. As a result, we undertook this study to assess the impact of e-cigarette, conventional tobacco, and dual use on sleep quality, sleep latency, cough, and drug use. Participants (n = 1198) were recruited through online surveys posted to social media sites with a monetary incentive. Participants were grouped by inhalant use, with 8% e-cigarette users, 12% conventional tobacco users, 30% dual users, and 51% non-smokers/non-vapers. Dual use of e-cigarettes and conventional tobacco was associated with increased sleep latency relative to non-smokers/non-vapers by multivariable linear regression (mean difference of 4.08; 95% CI: 1.12 to 7.05, raw p = 0.007, adjusted p = 0.042); however, dual usage was not significantly associated with sleep quality relative to non-smokers/non-vapers (mean difference 0.22, 95%CI: (−0.36, 0.80), raw p = 0.452, adjust p = 0.542). Dual use was also associated with a higher reporting of cough (p = 0.038), as well as increased marijuana (p < 0.001) and cocaine (p < 0.001) usage. This study demonstrates that  dual use is associated with longer sleep latency, and suggests that the shared component of nicotine may be a driver. Because sleep broadly impacts multiple aspects of human health, defining the associations of e-cigarettes and vaping devices on sleep is critical to furthering our understanding of their influence on the body.

Adolescents' Use of Nicotine-Free and Nicotine E-Cigarettes: A Longitudinal Study of Vaping Transitions and Vaper Characteristics

INTRODUCTION

Although adolescents' nicotine addiction from e-cigarettes is a concern, few studies differentiate between vaping with and without nicotine. This study examines the prevalence of nicotine and nicotine-free vaping, maps transitions between vaping behaviors, and assesses differences in the personal characteristics of vapers in a sample of Norwegian adolescents.

AIMS AND METHODS

Data came from a nationwide longitudinal study of adolescents (n = 2018) conducted in 2017 (T1), 2018 (T2), and 2019 (T3) (mean age: 14.2, 15.0, and 16.2). Using an online questionnaire, we measured vaping with and without nicotine, snus use, smoking, sensation-seeking, conduct problems, and levels of depression.

RESULTS

Past 12-month vaping prevalence was stable (12%, 13%, and 15%). Among adolescents reporting vaping at T1, 66% had used e-cigarettes without nicotine, 22% with nicotine, and 12% were unsure of nicotine content. Individual vaping trajectories were unstable: of nicotine-free vapers, 54% became non-users, while 14% became nicotine vapers from T1 to T2. From T2 to T3, 50% became non-users, while 17% became nicotine vapers. Of nicotine vapers, 39% became non-users from T1 to T2, while 46% became non-users from T2 to T3. Compared to nicotine-free vapers, nicotine vapers had more conduct problems (mean = 3.67 vs 2.17), had more symptoms of depression (mean = 11.38 vs 6.95), and comprised more past 30-day snus users (33% vs 14%) and cigarette users (33% vs 9%).

CONCLUSIONS

Adolescent vapers most commonly used e-cigarettes without nicotine, few of these transitioned into nicotine vaping, and a majority became non-users. Nicotine vapers were more likely to use other tobacco products and have more conduct problems and symptoms of depression compared to nicotine-free vapers.

IMPLICATIONS

Reporting the prevalence of nicotine-free vaping is critical for assessing nicotine exposure and subsequent risks of nicotine addiction. This multi-cohort longitudinal study showed that use of nicotine-free e-cigarettes is common among young vapers in Norway. Adolescents' vaping patterns-both with and without nicotine-are generally temporal and experimental. Despite the majority of nicotine vapers becoming non-users, they are characterized by having more conduct problems and poorer mental health, and they more often used other tobacco products.

Adolescents' Perceptions of Harmfulness of Tobacco and Tobacco-like Products in Finland

During the recent years, new tobacco and tobacco-like products, e.g., e-cigarettes, have emerged on the market. Adolescents often underestimate health risks in general, including those concerning tobacco. Little is known of adolescents' perceptions of health risks of the newer products. Our paper compares adolescents' perceptions of harmfulness of cigarettes, e-cigarettes, snus, water pipes, and nicotine in Finland, a country with a long history of strict tobacco control policy. Online surveys to nationally representative samples of 12-18-year-olds were conducted in 2017 and 2019, with 7578 answering the surveys. Only 3% of boys and 2% of girls did not agree that cigarettes are harmful to health. The percentages were slightly higher for snus (6% and 3%, respectively) and nicotine (12%, 8%) but much higher for e-cigarettes (30%, 22%) and water pipes (36%, 38%). Those who used the product, whose parents were smokers or had lower education, and whose school performance was lower, less often agreed with the harmful health effects of the products. Our results showed that adolescents understood the harmfulness of older tobacco products better than the harmfulness of the newer ones. Our results also showed the need to strengthen health education and fix adolescents' misperceptions of the health effects of the newer products.

Single, Dual, and Triple Use of Cigarettes, e-Cigarettes, and Snus among Adolescents in the Nordic Countries

New tobacco and nicotine products have emerged on the market in recent years. Most research has concerned only one product at a time, usually e-cigarettes, while little is known about the multiple use of tobacco and nicotine products among adolescents. We examined single, dual, and triple use of cigarettes, e-cigarettes, and snus among Nordic adolescents, using data of 15-16-year-olds (n = 16,125) from the European School Survey Project on Alcohol and other Drugs (ESPAD) collected in 2015 and 2019 from Denmark, Finland, Iceland, Norway, Sweden, and the Faroe Islands. Country-specific lifetime use of any of these products ranged between 40% and 50%, and current use between 17% and 31%. Cigarettes were the most common product in all countries except for Iceland, where e-cigarettes were remarkably more common. The proportion of dual and triple users was unexpectedly high among both experimental (24%-49%) and current users (31-42%). Triple use was less common than dual use. The users' patterns varied somewhat between the countries, and Iceland differed substantially from the other countries, with a high proportion of single e-cigarette users. More knowledge on the patterns of multiple use of tobacco and nicotine products and on the potential risk and protective factors is needed for targeted intervention and prevention efforts.

[Risk of initiation to smoking with the use of electronic cigarettes: systematic review and meta-analysis]

This article aims to evaluate the association between the use of electronic cigarettes and initiation to smoking, through a systematic review with meta-analysis of longitudinal studies. A bibliographic search was performed on the MEDLINE, Embase, LILACS and PsycInfo databases. Reference selection, data extraction and risk of bias assessment of the studies were independently carried out in pairs, and the disagreements were discussed with a third researcher to reach a consensus. Meta-analysis was performed using the Mantel-Haenszel random effects model. Among the 25 studies included, 22 evaluated the outcome of conventional cigarette experimentation and nine assessed the outcome of current smoking (in the last 30 days). The meta-analysis showed that the use of electronic cigarettes increased the risk of conventional cigarette experimentation by almost three and a half times (RR=3.42; 95%CI 2.81-4.15), and by more than four times the risk of current smoking (RR=4.32; 95%CI 3.13-5.94). The risk of smoking initiation is significantly higher among electronic cigarette users. The marketing authorization of such devices may represent a threat to public health policies in Brazil.

Association between electronic nicotine delivery systems and electronic non-nicotine delivery systems with initiation of tobacco use in individuals aged < 20 years. A systematic review and meta-analysis

BACKGROUND

This systematic review described the association between electronic nicotine delivery systems and electronic non-nicotine delivery systems (ENDS/ENNDS) use among non-smoking children and adolescents aged <20 years with subsequent tobacco use.

METHODS

We searched five electronic databases and the grey literature up to end of September 2020. Prospective longitudinal studies that described the association between ENDS/ENNDS use, and subsequent tobacco use in those aged < 20 years who were non-smokers at baseline were included. The Joanna Briggs Institute Critical Appraisal Checklist was used to assess risk of bias. Data were extracted by two reviewers and pooled using a random-effects meta-analysis. We generated unadjusted and adjusted risk ratios (ARRs) describing associations between ENDS/ENNDS and tobacco use.

FINDINGS

A total of 36 publications met the eligibility criteria, of which 25 were included in the systematic review (23 in the meta-analysis) after exclusion of overlapping studies. Sixteen studies had high to moderate risk of bias. Ever users of ENDS/ENNDS had over three times the risk of ever cigarette use (ARR 3·01 (95% CI: 2·37, 3·82; p<0·001, I2: 82·3%), and current cigarette use had over two times the risk (ARR 2·56 (95% CI: 1·61, 4·07; p<0·001, I2: 77·3%) at follow up. Among current ENDS/ENNDS users, there was a significant association with ever (ARR 2·63 (95% CI: 1·94, 3·57; p<0·001, I2: 21·2%)), but not current cigarette use (ARR 1·88 (95% CI: 0·34, 10·30; p = 0·47, I2: 0%)) at follow up. For other tobacco use, ARR ranged between 1·55 (95% CI 1·07, 2·23) and 8·32 (95% CI: 1·20, 57·04) for waterpipe and pipes, respectively. Additionally, two studies examined the use of ENNDS (non-nicotine devices) and found a pooled adjusted RR of 2·56 (95% CI: 0·47, 13·94, p = 0.035).

CONCLUSION

There is an urgent need for policies that regulate the availability, accessibility, and marketing of ENDS/ENNDS to children and adolescents. Governments should also consider adopting policies to prevent ENDS/ENNDS uptake and use in children and adolescents, up to and including a ban for this group.

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

Objective

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

Data sources

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

Study selection

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

Data synthesis

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

Conclusions

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

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

Electronic cigarette use among 14- to 17-year-olds in Europe

BACKGROUND

Studies comparing adolescent e-cigarette use in different countries are scarce. We study students' e-cigarette and conventional cigarette ever-use, their social correlates and e-liquid use in seven EU countries.

METHODS

SILNE-R data (N=12 167, response rate 79.4%) of 14-17-year-olds from Amersfoort (NL), Coimbra (PT), Dublin (IR), Hanover (GE), Latina (IT), Namur (BE) and Tampere (FI) were used. E-cigarette and conventional cigarette ever-use, dual-use, type of e-liquid and social correlates were measured with a school survey and analyzed with cross-tabulations and multinomial logistic regression.

RESULTS

About 34% had tried e-cigarettes, but the variation was large between the cities (Latina 50%; Hanover 23%). Of e-cigarette ever-users, 37% had used nicotine e-liquid, 43% exclusively non-nicotine liquid and 20% did not know the content. Nicotine e-liquid was more prevalent among monthly e-cigarette users and weekly smoking e-cigarette users. The social correlates were mainly the same for exclusive e-cigarette ever-use, exclusive conventional cigarette ever-use and dual-use. Boys had greater odds for exclusive e-cigarette and dual-use compared to girls. Of social correlates, low academic achievement and parental smoking were positively associated with all categories of use, but parental education and immigrant background were not. The strongest association was found between peer smoking (most/all best friends smoke) and dual-use (OR 34.29).

CONCLUSIONS

Students' e-cigarette ever-use varies greatly between EU countries. E-cigarettes seem not to be a substitute for conventional cigarettes but more a complementary product. Tobacco control policies might also prevent e-cigarette use but specific regulations on e-cigarettes are needed to prevent nicotine addiction originating from them.

Nicotine Inhalation and Suicide: Clinical Correlates and Behavioral Mechanisms

BACKGROUND AND OBJECTIVES

Extensive evidence links smoking and suicide independently of psychiatric diagnoses, but there are questions about the pathophysiology and specificity of this relationship. We examined characteristics of this linkage to identify potential transdiagnostic mechanisms in suicide and its prevention.

METHODS

We reviewed literature that associated suicide with smoking and e-cigarettes, including the temporal sequence of smoking and suicide risk and their shared behavioral risk factors of sensitization and impulsivity.

RESULTS

Smoking is associated with increased suicide across psychiatric diagnoses and in the general population, proportionately to the number of cigarettes smoked per day. Rapid nicotine uptake into the brain through inhalation of conventional cigarettes, electronic cigarettes (e-cigarette), or even second-hand smoke can facilitate long-term sensitization and short-term impulsivity. Both impair action regulation and predispose to negative affect, continued smoking, and suicidal behavior. Intermittent hypoxia, induced by cigarettes or e-cigarettes, synergistically promotes impulsivity and sensitization, exacerbating suicidality. Two other shared behavioral risks also develop negative urgency (combined impulsivity and negative affect) and cross-sensitization to stressors or to other addictive stimuli. Finally, early smoking onset, promoted by e-cigarettes in never-smokers, increases subsequent suicide risk.

CONCLUSION AND SCIENTIFIC SIGNIFICANCE

Prevention or cessation of nicotine inhalation can strategically prevent suicidality and other potentially lethal behavior regardless of psychiatric diagnoses. Medications for reducing smoking and suicidality, especially in younger smokers, should consider the neurobehavioral mechanisms for acute impulsivity and longer-term sensitization, potentially modulated more effectively through glutamate antagonism rather than nicotine substitution. (Am J Addict 2021;30:316-329).

Association between electronic cigarette use and tobacco cigarette smoking initiation in adolescents: a systematic review and meta-analysis

BACKGROUND

This systematic review of prospective longitudinal primary studies sought to determine whether electronic cigarette (e-cigarette) use by teenagers who had never smoked conventional tobacco cigarettes (tobacco cigarettes) at baseline was associated with subsequently commencing tobacco cigarette smoking.

METHODS

The review followed the principles of a systematic review and meta-analysis. A key word search identified peer-reviewed articles published between 1 January 2005 and 2 October 2019 from seven bibliographic databases and one search engine. Using pre-prepared inclusion/exclusion criteria two researchers independently screened abstracts, and subsequently, full text papers. Selected articles were quality assessed in duplicate. Data on study participants characteristics, exposure and outcome measures were recorded in an adapted Cochrane Data Extraction Form. Feasibility assessment was done to detect clinical heterogeneity and choose an approach to meta-analysis. Analysis comprised pairwise random effects meta-analyses, and sensitivity and subgroup analyses.

RESULTS

From the 6619 studies identified, 14 one-off primary studies in 21 articles were suitable for inclusion. The participants ages ranged from 13 to 19 years and comprised teenagers based in Europe and North America. Nine of the 14 one-off studies, with follow-up periods between 4 and 24 months, met the criteria for inclusion in a meta-analysis of the association between ever use of e-cigarettes and subsequent initiation of tobacco cigarette use. Based on primary study adjusted odds ratios, our meta-analysis calculated a 4.06 (95% confidence interval (CI): 3.00-5.48, I2 68%, 9 primary studies) times higher odds of commencing tobacco cigarette smoking for teenagers who had ever used e-cigarettes at baseline, though the odds ratio were marginally lower (to 3.71 times odds, 95%CI: 2.83-4. 86, I2 35%, 4 primary studies) when only the four high-quality studies were analysed.

CONCLUSION

The systematic review found that e-cigarette use was associated with commencement of tobacco cigarette smoking among teenagers in Europe and North America, identifying an important health-related harm. Given the availability and usage of e-cigarettes, this study provides added support for urgent response by policymakers to stop their use by teenagers to decrease direct harms in this susceptible population group, as well as to conserve achievements in diminishing tobacco cigarette initiation.

E-cigarette use and combustible tobacco cigarette smoking uptake among non-smokers, including relapse in former smokers: umbrella review, systematic review and meta-analysis

OBJECTIVE

To review and summarise the current evidence on the uptake of combustible cigarette smoking following e-cigarette use in non-smokers-including never-smokers, people not currently smoking and past smokers-through an umbrella review, systematic review and meta-analysis.

DESIGN

Umbrella review, systematic review and meta-analysis.

DATA SOURCES

PubMed, Scopus, Web of Science, PsychINFO (Ovid), Medline (Ovid) and Wiley Cochrane Library up to April 2020.

RESULTS

Of 6225 results, 25 studies of non-smokers-never, not current and former smokers-with a baseline measure of e-cigarette use and an outcome measure of combustible smoking uptake were included. All 25 studies found increased risk of smoking uptake with e-cigarette exposure, although magnitude varied substantially. Using a random-effects model, comparing e-cigarette users versus non-e-cigarette users, among never-smokers at baseline the OR for smoking initiation was 3.25 (95% CI 2.61 to 4.05, I2 85.7%) and among non-smokers at baseline the OR for current smoking was 2.87 (95% CI 1.97 to 4.19, I2 90.1%). Among former smokers, smoking relapse was higher in e-cigarette users versus non-users (OR=2.40, 95% CI 1.50 to 3.83, I2 12.3%).

CONCLUSIONS

Across multiple settings, non-smokers who use e-cigarettes are consistently more likely than those avoiding e-cigarettes to initiate combustible cigarette smoking and become current smokers. The magnitude of this risk varied, with an average of around three times the odds. Former smokers using e-cigarettes have over twice the odds of relapse as non-e-cigarettes users. This study is the first to our knowledge to review and pool data on the latter topic.

PROSPERO REGISTRATION NUMBER

CRD42020168596.

Critical appraisal of the European Union Scientific Committee on Health, Environmental and Emerging Risks (SCHEER) Preliminary Opinion on electronic cigarettes

BACKGROUND

In preparation for the 2021 revision of the European Union Tobacco Products Directive, the Scientific Committee on Health, Environmental and Emerging Risks (SCHEER) has posted its Preliminary Opinion on Electronic Cigarettes. They concluded that e-cigarettes only achieve a sub-optimal level of protection of human health. In this paper, we provide evidence that the Opinion's conclusions are not adequately backed up by scientific evidence and did not discuss the potential health benefits of using alternative combustion-free nicotine-containing products as substitute for tobacco cigarettes.

METHODS

Searches for articles were conducted in PubMed and by citation chasing in Google Scholar. Articles were also retrieved with a review of references in major publications. Primary data from World Health Organization surveys, the conclusions of reviews, and peer-reviewed non-industry studies were cited to address errors and omissions identified in the Opinion.

RESULTS

The Opinion omitted reporting on the individual and population health benefits of the substitution of e-cigarettes (ENDS) for cigarette smoking. Alternative hypotheses to the gateway theory were not evaluated. Its assessment of cardiovascular risk is contradicted by numerous reviews. It cites ever-use data that do not represent current patterns of use. It did not report non-nicotine use. It presented erroneous statements on trends in ENDS prevalence. It over-emphasized the role of flavours in youth ENDS initiation. It did not discuss cessation in sufficient length.

CONCLUSIONS

For the delivery of a robust and comprehensive final report, the members of the Working Group of the Scientific Committee on Health, Environmental and Emerging Risks will need to consider (1) the potential health benefits of ENDS substitution for cigarette smoking, (2) alternative hypotheses and contradictory studies on the gateway effect, (3) its assessment of cardiovascular risk, (4) the measurements of frequency of use, (5) non-nicotine use, (6) the role of flavours, and (7) a fulsome discussion of cessation.

Association of initial e-cigarette and other tobacco product use with subsequent cigarette smoking in adolescents: a cross-sectional, matched control study

INTRODUCTION

This study assessed whether initiating e-cigarette use increases the uptake of cigarette smoking in US adolescents compared with behavioural and synthetic controls.

METHODS

Data come from 78 265 adolescents in the National Youth Tobacco Survey (2014-2017) of whom 38 630 provided information about the first tobacco product they had used in 2014/15. Ever, past 30 day and established (30 day use and 100+ lifetime cigarettes) cigarette smoking was compared in adolescents who first used an e-cigarette (exposure group), a non-cigarette combustible (CT) or other non-combustible tobacco (NT) product (behavioural controls), and propensity score matched adolescents without initial e-cigarette use (synthetic controls).

RESULTS

Relative to behavioural controls, adolescents who tried e-cigarettes first were less likely to have ever smoked cigarettes (26% vs CT (42.4%; OR 0.48, 95% CI 0.40 to 0.57), or NT initiators (52.7%; OR 0.32, 95% CI 0.26 to 0.39)), to be past 30 day (6% vs CT (11.9%; OR 0.48, 95% CI 0.36 to 0.62), or NT initiators (20.0%; OR 0.26, 95% CI 0.19 to 0.35)) or be established cigarette smokers (0.7% vs CT (3.9%; OR 0.17, 95% CI 0.10 to 0.30), or NT initiators (8.4%; OR 0.08, 95% CI 0.04 to 0.13)). E-cigarette initiators were also less likely than synthetic controls (without initial e-cigarette use) to have ever smoked cigarettes (OR 0.76, 95% CI 0.62 to 0.93), be past 30 day (OR 0.71, 95% CI 0.55 to 0.91) or be established cigarette smokers (OR 0.26, 95% CI 0.13 to 0.51).

CONCLUSION

Less than 1% of US adolescents who use e-cigarettes first were established cigarette smokers. They were less likely to be smokers than adolescents who tried other combustible or non-combustible tobacco products first and propensity score matched adolescents without initial e-cigarette use.

Electronic Cigarette Use and Its Relationship with Smoking and Alcohol and Illicit Drug Consumption among Romanian University Students

Background and objectives: This study assesses electronic cigarette (e-cigarette) use and its relationship with smoking and alcohol and illicit drug consumption among Romanian university students. Materials and methods: A cross sectional study using anonymous questionnaire was performed in 2017 among 400 university students from Cluj-Napoca, Romania. Results: 95.5% of the participants had heard about e-cigarettes and 43.7% of these had tried e-cigarettes during their lifetime, while 8.9% declared using cigarettes in the previous month (one out of five students who had tried them during their lifetime). Half of the students had smoked during their lifetime and one third had smoked in the previous month. Eighty-five percent of participants had experimented alcohol intoxication during their lifetime and 45% had done so in the previous month, while illicit drug use during their lifetime and the previous month was 34% and 9.5%, respectively. The results of the linear regression analyses show a positive correlation between e-cigarette use, smoking, experimentation with alcohol intoxication, and the use of illicit drugs. Conclusions: Future studies as well as educational activities should address the complex relationship between e-cigarette and other substance use among Romanian youth.

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

INTRODUCTION

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Further investigation of gateway effects using the PATH study

Background: Interest exists in whether youth e-cigarette use (“vaping”) increases risk of initiating cigarette smoking. Using Waves 1 and 2 of the US PATH study we previously reported adjustment for vaping propensity using Wave 1 variables explained about 80% of the unadjusted relationship. Here data from Waves 1 to 3 are used to avoid over-adjustment if Wave 1 vaping affected variables recorded then.

Methods: Main analyses M1 and M2 concerned Wave 2 never smokers who never vaped by Wave 1, linking Wave 2 vaping to Wave 3 smoking initiation, adjusting for predictors of vaping based on Wave 1 data using differing  propensity indices.  M3 was similar but derived the index from Wave 2 data.  Sensitivity analyses excluded Wave 1 other tobacco product users, included other product use as another predictor, or considered propensity for smoking or any tobacco use, not vaping. Alternative analyses used exact age (not previously available) as a confounder not grouped age, attempted residual confounding adjustment by modifying predictor values using data recorded later, or considered interactions with age.

Results: In M1, adjustment removed about half the excess OR (i.e. OR–1), the unadjusted OR, 5.60 (95% CI 4.52-6.93), becoming 3.37 (2.65-4.28), 3.11 (2.47-3.92) or 3.27 (2.57-4.16), depending whether adjustment was for propensity as a continuous variable, as quintiles, or the variables making up the propensity score. Many factors had little effect: using grouped or exact age; considering other products; including interactions; or using predictors of smoking or tobacco use rather than vaping. The clearest conclusion was that analyses avoiding over-adjustment explained about half the excess OR, whereas analyses subject to over-adjustment explained about 80%.

Conclusions: Although much of the unadjusted gateway effect results from confounding, we provide stronger evidence than previously of some causal effect of vaping, though doubts still remain about the completeness of adjustment.

Unique, long-term effects of nicotine on adolescent brain

Adolescence is a time of major plasticity of brain systems that regulate motivated behavior and cognition, and is also the age of peak onset of nicotine use. Although there has been a decline in teen use of cigarettes in recent years, there has been a huge increase in nicotine vaping. It is therefore critically important to understand the impact of nicotine on this critical phase of brain development. Animal studies have shown that nicotine has unique effects on adolescent brain. The goal of this review is therefore to systematically evaluate age- and sex-differences in the effects of nicotine on brain and behavior. Both acute and chronic effects of nicotine on brain biochemistry and behavior, particularly drug reward, aversion, cognition and emotion, are evaluated. Gaps in our current knowledge that need to be addressed are also highlighted. This review compares and integrates human and animals findings. Although there can be no experimental studies in humans to confirm similar behavioral effects of teen nicotine exposure, an emerging observational literature suggests similarities across species. Given the substantial evidence for long-term negative impact of adolescent nicotine exposure on brain and behavior, further longitudinal assessment of health outcomes in teen and young adult e-cigarette users is warranted.

The Effects of Nicotine on Development

Recently, there has been a significant increase in the use of noncombustible nicotine-containing products, including electronic cigarettes (e-cigarettes). Of increasing popularity are e-cigarettes that can deliver high doses of nicotine over short periods of time. These devices have led to a rise in nicotine addiction in adolescent users who were nonsmokers. Use of noncombustible nicotine products by pregnant mothers is also increasing and can expose the developing fetus to nicotine, a known teratogen. In addition, young children are frequently exposed to secondhand and thirdhand nicotine aerosols generated by e-cigarettes, with little understanding of the effects these exposures can have on health. With the advent of these new nicotine-delivery systems, many concerns have arisen regarding the short- and long-term health effects of nicotine on childhood health during all stages of development. Although health studies on nicotine exposure alone are limited, educating policy makers and health care providers on the potential health effects of noncombustible nicotine is needed because public acceptance of these products has become so widespread. Most studies evaluating the effects of nicotine on health have been undertaken in the context of smoke exposure. Nevertheless, in vitro and in vivo preclinical studies strongly indicate that nicotine exposure alone can adversely affect the nervous, respiratory, immune, and cardiovascular systems, particularly when exposure occurs during critical developmental periods. In this review, we have included both preclinical and clinical studies to identify age-related health effects of nicotine exposure alone, examining the mechanisms underlying these effects.

Investigating gateway effects using the PATH study

BACKGROUND

A recent meta-analysis of nine cohort studies in youths reported that baseline ever e-cigarette use strongly predicted cigarette smoking initiation in the next 6-18 months, with an adjusted odds ratio of 3.62 (95% confidence interval 2.42-5.41).  A recent review of e-cigarettes agreed there was substantial evidence for this "gateway effect".  However, the number of confounders considered in the studies was limited, so we investigated whether the effect might have resulted from inadequate adjustment, using Waves 1 and 2 of the Population Assessment of Tobacco and Health study.

METHODS

Our main analyses considered Wave 1 never cigarette smokers who, at Wave 2, had information available on smoking initiation.  We constructed a propensity score for ever e-cigarette use from Wave 1 variables, using this to predict ever cigarette smoking.  Sensitivity analyses accounted for use of other tobacco products, linked current e-cigarette use to subsequent current smoking, or used propensity scores for ever smoking or ever tobacco product use as predictors.  We also considered predictors using data from both waves to attempt to control for residual confounding from misclassified responses.

RESULTS

Adjustment for propensity dramatically reduced the unadjusted odds ratio (OR) of 5.70 (4.33-7.50) to 2.48 (1.85-3.31), 2.47 (1.79-3.42) or 1.85 (1.35-2.53), whether adjustment was made as quintiles, as a continuous variable or for the individual variables.  Additional adjustment for other tobacco products reduced this last OR to 1.59 (1.14-2.20).  Sensitivity analyses confirmed adjustment removed most of the gateway effect.  Control for residual confounding also reduced the association.

CONCLUSIONS

We found that confounding is a major factor, explaining most of the observed gateway effect.  However, our analyses are limited by small numbers of new smokers considered and the possibility of over-adjustment if taking up e-cigarettes affects some predictor variables.  Further analyses are intended using Wave 3 data which should avoid these problems.

Investigating gateway effects using the PATH study

BACKGROUND

A recent meta-analysis of nine cohort studies in youths reported that baseline ever e-cigarette use strongly predicted cigarette smoking initiation in the next 6-18 months, with an adjusted odds ratio of 3.62 (95% confidence interval 2.42-5.41).  A recent review of e-cigarettes agreed there was substantial evidence for this "gateway effect".  However, the number of confounders considered in the studies was limited, so we investigated whether the effect might have resulted from inadequate adjustment, using Waves 1 and 2 of the Population Assessment of Tobacco and Health study.

METHODS

Our main analyses considered Wave 1 never cigarette smokers who, at Wave 2, had information available on smoking initiation.  We constructed a propensity score for ever e-cigarette use from Wave 1 variables, using this to predict ever cigarette smoking.  Sensitivity analyses accounted for use of other tobacco products, linked current e-cigarette use to subsequent current smoking, or used propensity scores for ever smoking or ever tobacco product use as predictors.  We also considered predictors using data from both waves to attempt to control for residual confounding from misclassified responses.

RESULTS

Adjustment for propensity dramatically reduced the unadjusted odds ratio (OR) of 5.70 (4.33-7.50) to 2.48 (1.85-3.31), 2.47 (1.79-3.42) or 1.85 (1.35-2.53), whether adjustment was made as quintiles, as a continuous variable or for the individual variables.  Additional adjustment for other tobacco products reduced this last OR to 1.59 (1.14-2.20).  Sensitivity analyses confirmed adjustment removed most of the gateway effect.  Control for residual confounding also reduced the association.

CONCLUSIONS

We found that confounding is a major factor, explaining most of the observed gateway effect.  However, our analyses are limited by small numbers of new smokers considered and the possibility of over-adjustment if taking up e-cigarettes affects some predictor variables.  Further analyses are intended using Wave 3 data which should avoid these problems.