Is Adolescent E-Cigarette Use Associated With Subsequent Smoking? A New Look

Increased e-cigarette use prevalence is associated with decreased smoking prevalence among US adults

BACKGROUND

If US adults who smoke cigarettes are switching to e-cigarettes, the effect may be observable at the population level: smoking prevalence should decline as e-cigarette prevalence increases, especially in sub-populations with highest e-cigarette use. This study aimed to assess such effects in recent nationally-representative data.

METHODS

We updated a prior analysis with the latest available National Health Interview Survey data through 2022. Data were cross-sectional estimates of the yearly prevalence of smoking and e-cigarette use, respectively, among US adults and among specific age, race/ethnicity, and sex subpopulations. Non-linear models were fitted to observed smoking prevalence in the pre-e-cigarette era, with a range of 'cut-off' years explored (i.e., between when e-cigarettes were first introduced to when they became widely available). These trends were projected forward to predict what smoking prevalence would have been if pre-e-cigarette era trends had continued uninterrupted. The difference between actual and predicted smoking prevalence ('discrepancy') was compared to e-cigarette use prevalence in each year in the e-cigarette era to investigate whether the observed decline in smoking was statistically associated with e-cigarette use.

RESULTS

Observed smoking prevalence in the e-cigarette era was significantly lower than expected based on pre-e-cigarette era trends; these discrepancies in smoking prevalence grew as e-cigarette use prevalence increased, and were larger in subpopulations with higher e-cigarette use, especially younger adults aged 18-34. Results were robust to sensitivity tests varying the analysis design.

CONCLUSIONS

Population-level data continue to suggest that smoking prevalence has declined at an accelerated rate in the last decade in ways correlated with increased uptake of e-cigarette use.

The "Gateway" hypothesis: evaluation of evidence and alternative explanations

BACKGROUND

Electronic nicotine delivery systems (ENDS) offer a substantial harm reduction opportunity for adults who smoke and are unlikely to quit. However, a major concern about ENDS is their use by non-smoking youth, and particularly whether ENDS are acting as a "gateway" that leads youth to later start smoking cigarettes. However, evidence for the gateway hypothesis can be interpreted in alternative ways, e.g. that youth who have certain characteristics were already predisposed to use both ENDS and cigarettes ("common liability" explanation).

AIMS

This commentary provides an evaluation of the gateway hypothesis that is accessible by a lay audience. This paper first reviews and evaluates the evidence interpreted as supporting the gateway hypothesis. Important alternative explanations (i.e., common liability) are discussed, as are different types of evidence (i.e., population-level trends) that can help differentiate between these competing explanations.

OVERVIEW

Evidence for the gateway hypothesis is based on the finding that youth who use ENDS are more likely to also smoke cigarettes. However, this evidence suffers from an important flaw: these studies fail to fully account for some youths' pre-existing tendency to use products containing nicotine, and inappropriately interpret the results as ENDS use causing some youth to smoke. Common liability studies suggest that ENDS use does not, in and of itself, directly cause youth to later smoke cigarettes, beyond their pre-existing tendency to use products containing nicotine. Population-level trends show that youth cigarette smoking declined faster after ENDS use became common, which contradicts the central prediction of the gateway hypothesis (i.e. that youth smoking would be more common following ENDS uptake, than otherwise be expected).

CONCLUSION

Evidence offered in support of the gateway hypothesis does not establish that ENDS use causes youth to also smoke cigarettes. Instead, this evidence is better interpreted as resulting from a common liability to use both ENDS and cigarettes. Population-level trends are inconsistent with the gateway hypothesis, and instead are consistent with (but do not prove) ENDS displacing cigarettes. Policies based on misinterpreting a causal gateway effect may be ineffective at best, and risk the negative unintended consequence of increased cigarette smoking.

A systematic review and meta-analysis of the association between e-cigarette use among non-tobacco users and initiating smoking of combustible cigarettes

INTRODUCTION

The rapid increase in e-cigarette use over the past decade has triggered an important public health question on the potential association between e-cigarette use and combustible cigarette smoking. Following AMSTAR 2 and PRISMA guidelines, this evidence synthesis sought to identify and characterize any associations between e-cigarette use among individuals not smoking cigarettes and initiation of cigarette smoking.

METHODS

The protocol was registered on September 24, 2018 (PROSPERO 2018 CRD42018108540). Three databases were queried from January 01, 2007 to April 26, 2023. Search results were screened using the PICOS review method.

RESULTS

Among 55 included studies (40 "good" and 15 "fair"; evidence grade: "high") that adjusted for gender, age, and race/ethnicity between groups, generally, there was a significant association between non-regular e-cigarette use and initiation of cigarette smoking, further supported by the meta-analytic results (AOR 3.71; 95% CI 2.86-4.81). However, smoking initiation was most often measured as ever/current cigarette smoking. Two studies (quality: 2 "good") evaluated progression to regular cigarette smoking among individuals with regular use of e-cigarettes, and generally found no significant associations. One study ("good") evaluated smoking initiation among individuals with regular use of e-cigarettes, finding an increasing probability of ever smoking cigarettes with increased e-cigarette use. Twelve studies (10 "good" and two "fair") examining progression to regular smoking among individuals with non-regular use of e-cigarettes reported inconsistent findings.

CONCLUSIONS

Numerous methodological flaws in the body of literature limit the generalizability of these results to all individuals who are not smoking cigarettes with few studies measuring established/regular use/smoking of e-cigarettes and cigarettes. Further, studies did not control adequately for specific confounding variables representing common liabilities between e-cigarette use and cigarette smoking, nor did they account for sufficient follow-up durations. Collectively, these flaws limit the generalizability of findings to the question of an association between e-cigarette use and cigarette smoking initiation.

Vaping: Public Health, Social Media, and Toxicity

This viewpoint aims to provide a comprehensive understanding of vaping from various perspectives that contribute to the invention, development, spread, and consequences of e-cigarette products and vaping. Our analysis showed that the specific characteristics of e-cigarette products as well as marketing strategies, especially social media marketing, fostered the spread of vaping and the subsequent effects on human health and toxicity. We analyzed the components of e-cigarette devices and e-liquids, including the latest variants whose impacts were often overlooked. The different forms of nicotine, including salts and freebase nicotine, tobacco-derived nicotine, tobacco-free nicotine, and cooling agents (WS3 and WS23), have brought more choices for vapers along with more ways for e-cigarette manufacturers to advertise false understandings and present a greater threat to vapers' health. Our work emphasized the products of brands that have gained significant influence recently, which are contributing to severe public health issues. On the other hand, we also discussed in detail the toxicity of e-liquid components and proposed a toxicity mechanism. We also noticed that nicotine and other chemicals in e-liquids promote each other's negative effects through the oxidative stress and inflammatory nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) pathway, a mechanism leading to pulmonary symptoms and addiction. The impact of government regulations on the products themselves, including flavor bans or regulations, has been limited. Therefore, we proposed further interventions or harm reduction strategies from a public health perspective.

Vuse Solo e-cigarettes do not provide net benefits to public health: a scientific analysis of FDA's marketing authorisation

In October 2021, the US Food and Drug Administration (FDA) authorised marketing of RJ Reynolds Vapor Company's (RJR) Vuse Solo e-cigarette through FDA's Premarket Tobacco Product Application (PMTA) pathway. FDA concluded that RJR demonstrated Vuse products met the statutory standard of providing a net benefit to public health. A review of FDA's scientific justification reveals deficiencies: (1) not adequately considering Vuse's popularity with youth and evidence that e-cigarettes expanded the nicotine market and stimulate cigarette smoking; (2) trading youth addiction for unproven adult benefit without quantifying these risks and benefits; (3) not considering design factors that appeal to youth; (4) not addressing evidence that e-cigarettes used as consumer products do not help smokers quit and promote relapse in former smokers; (5) not discussing evidence that dual use is more dangerous than smoking; (6) narrowly focusing on the fact that e-cigarettes deliver lower levels of some toxicants without addressing direct evidence on adverse health effects; (7) downplaying significant evidence of other substantial harms; (8) not acting on FDA's own study showing no all-cause mortality benefit of reducing (but not stopping) cigarette use; and (9) improperly considering e-cigarettes' high abuse liability and potential for high youth addiction and undermining tobacco cessation. Because marketing these products is not appropriate for the protection of the public health, FDA should reconsider its Vuse marketing order as statutorily required and not use it as a template for other e-cigarette PMTAs. Policymakers outside the USA should anticipate that tobacco companies will use FDA's decision to try to weaken tobacco control regulation of e-cigarettes and promote their products.

What Substances Are Adolescents Vaping? Estimating Nicotine-Specific and Cannabis-Specific Vaping from US National Youth Surveys

BACKGROUND

Youth use of electronic cigarettes ("e-cigarettes") is an ongoing concern. Vaping is usually assumed to be of nicotine, but survey responses may also include vaping of non-nicotine substances (particularly cannabis), which can impose different risks. The current study quantifies the proportions of nicotine-specific and cannabis-specific vaping among adolescents.

METHODS

Data from the Monitoring the Future (MTF) 2021 survey were analyzed with respect to the substance vaped: nicotine, cannabis, or flavoring only. Past-30-day (P30D) nicotine-specific vaping (exclusively, or also having vaped other substances) and cannabis-specific vaping were calculated. Results were also broken down by grade level, cigarette smoking history (current, former, or never), and frequency of e-cigarette use (<20 vs. 20+ days in P30D).

RESULTS

Among 4706 P30D e-cigarette users, 84.2% vaped nicotine; the remaining 15.8% reported not vaping any nicotine in P30D. Cannabis vaping was reported by 48.4% of P30D vapers. Vaping both nicotine and cannabis in P30D was more common in current and former smokers than in never-smokers, and in frequent vapers (of any substance). Conversely, never-smokers were more commonly vaping cannabis but not nicotine, compared to current and former smokers. Supplementary NYTS 2022 analyses were consistent with these findings.

CONCLUSIONS

A notable proportion of self-reported P30D vapers reported not vaping nicotine; nearly half vaped cannabis. Capturing the variety of substances used in vaping devices is imperative for accurate public health surveillance of both nicotine and cannabis vaping among US adolescents, considering their different respective harms and regulatory frameworks.

The interaction of e-cigarette use and mental health symptoms on risk of cigarette smoking initiation among young adults in the United States

BACKGROUND AND AIMS

It is unknown whether young adults who vape nicotine and have poor mental health have greater risk of smoking initiation than expected based on individual risks of vaping and mental health alone. This study aimed to estimate the joint association of vaping and mental health symptoms with smoking initiation among young adults, and test for additive interaction between vaping and mental health in smoking initiation risk.

DESIGN

Using five waves of the Population Assessment of Tobacco and Health (wave 1, 2013-2014; wave 2, 2014-2015; wave 3, 2015-2016; wave 4, 2016-2018; wave 5, 2018-2019), we estimated risk differences (RD) for the association of time-varying and time-lagged vaping and internalizing (e.g., anxiety, depressive) and externalizing (e.g., inattention/hyperactivity) mental health symptoms with cigarette smoking initiation at follow-up, over four 1-year intervals. We calculated interaction contrasts (IC) to estimate the excess risk of smoking initiation attributable to the interaction of vaping and mental health symptoms.

SETTING

United States.

PARTICIPANTS

A total of 6908 cigarette-naïve individuals aged 18-24 years.

MEASUREMENTS

Exposures included current (past-30 day) vaping and internalizing and externalizing mental health symptoms (high vs moderate/low symptoms). The outcome was smoking initiation (ever cigarette use) after 1 year.

FINDINGS

The per-interval risk of smoking initiation was 7.6% (1039 cases/13 712 person-intervals). Compared with noncurrent vaping and moderate/low mental health symptoms, adjusted RDs for current vaping and high mental health symptoms were 17.2% (95% confidence interval [CI]: 7.2% to 27.3%) for internalizing and 18.7% (95%CI: 8.1% to 29.2%) for externalizing symptoms. The excess risk attributed to interaction of current vaping and high externalizing symptoms was IC = 11.3% (95%CI: 1.3% to 21.2%; P = 0.018), with inconclusive findings for internalizing symptoms (IC = 7.7% [95%CI: -2.2% to 17.7%; P = 0.097]).

CONCLUSIONS

There is possible, but inconclusive, superadditivity between vaping and mental health in risk of smoking initiation among young adults in the United States.

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.

Implications of nicotine vaping products for tobacco control in ASEAN low-income and middle-income countries: in-depth interviews with experts from the region

OBJECTIVES

The use of nicotine vaping products (NVPs) has increased in low-income and middle-income countries (LMICs) in the Association of Southeast Asian Nations (ASEAN) region; however, it is uncertain what implications the presence and use of NVPs have for tobacco control.

DESIGN

In-depth interviews were conducted to explore ASEAN tobacco control experts' (n=11) views on the rise of NVP use in ASEAN LMICs, current NVP policies, the potential harm reduction and smoking cessation utilities of these devices, and what implications they may have for tobacco control. Data were analysed using inductive, reflexive thematic analysis.

RESULTS

Five themes emerged: (1) NVPs threaten tobacco control in ASEAN LMICs; (2) commercial factors influence youth appeal and access: product attributes, marketing, supply chains; (3) opposition to the smoking cessation and harm reduction utilities of NVPs; (4) policies are inconsistent and fragmented in the region; and (5) tobacco industry power and tactics have been used to capture NVP markets.

CONCLUSIONS

ASEAN tobacco control experts believe that NVPs pose a threat to youth and non-smokers in LMICs in the region, largely because of tobacco industry NVP marketing activities. They do not support the use of NVPs for smoking cessation or harm reduction and call for more restrictions and consistent policy enforcement across the region to protect young people, while also cautiously recognising that use of NVPs may have some benefits for smokers.

Are the Relevant Risk Factors Being Adequately Captured in Empirical Studies of Smoking Initiation? A Machine Learning Analysis Based on the Population Assessment of Tobacco and Health Study

INTRODUCTION

Cigarette smoking continues to pose a threat to public health. Identifying individual risk factors for smoking initiation is essential to further mitigate this epidemic. To the best of our knowledge, no study today has used machine learning (ML) techniques to automatically uncover informative predictors of smoking onset among adults using the Population Assessment of Tobacco and Health (PATH) study.

AIMS AND METHODS

In this work, we employed random forest paired with Recursive Feature Elimination to identify relevant PATH variables that predict smoking initiation among adults who have never smoked at baseline between two consecutive PATH waves. We included all potentially informative baseline variables in wave 1 (wave 4) to predict past 30-day smoking status in wave 2 (wave 5). Using the first and most recent pairs of PATH waves was found sufficient to identify the key risk factors of smoking initiation and test their robustness over time. The eXtreme Gradient Boosting method was employed to test the quality of these selected variables.

RESULTS

As a result, classification models suggested about 60 informative PATH variables among many candidate variables in each baseline wave. With these selected predictors, the resulting models have a high discriminatory power with the area under the specificity-sensitivity curves of around 80%. We examined the chosen variables and discovered important features. Across the considered waves, two factors, (1) BMI, and (2) dental and oral health status, robustly appeared as important predictors of smoking initiation, besides other well-established predictors.

CONCLUSIONS

Our work demonstrates that ML methods are useful to predict smoking initiation with high accuracy, identifying novel smoking initiation predictors, and to enhance our understanding of tobacco use behaviors.

IMPLICATIONS

Understanding individual risk factors for smoking initiation is essential to prevent smoking initiation. With this methodology, a set of the most informative predictors of smoking onset in the PATH data were identified. Besides reconfirming well-known risk factors, the findings suggested additional predictors of smoking initiation that have been overlooked in previous work. More studies that focus on the newly discovered factors (BMI and dental and oral health status,) are needed to confirm their predictive power against the onset of smoking as well as determine the underlying mechanisms.

The Association Between Cannabis Use and Subsequent Nicotine Electronic Cigarette Use Among US Adolescents

PURPOSE

The current study assessed the association between cannabis use among youth never e-cigarette users and subsequent e-cigarette use.

METHODS

The Population Assessment of Tobacco and Health Study is a nationally representative cohort study. Participants aged 12 years and older were selected using a 4-stage, stratified probability sample design from the US civilian, noninstitutionalized population. We included adolescents who participated in both wave 4.5 (2017-2018) and wave 5 (2018-2019) of Population Assessment of Tobacco and Health, and were never e-cigarette users at baseline (N = 9,925). Through multivariable logistic regressions, we examined the prospective association between cannabis use and subsequent e-cigarette use.

RESULTS

E-cigarette use at wave five was significantly more common among youth cannabis users at wave 4.5. The adjusted relative risks between ever cannabis use and subsequent past 12-month, past 30-day, and frequent e-cigarette use (≥20 days per month) were 1.53 (95% CI, 1.26-1.81), 1.70 (95% CI, 1.25-2.15), and 2.10 (95% CI, 1.17-3.03), respectively. The adjusted relative risks between past 30-day cannabis use and subsequent past 12-month, past 30-day, and frequent e-cigarette use were 1.54 (95% CI, 1.04-2.28), 2.01 (95% CI, 1.23-3.29), and 2.87 (95% CI, 1.44-5.71), respectively. We also found significant associations between ever cannabis vaping with subsequent e-cigarette use.

DISCUSSION

While previous research associates e-cigarette use with subsequent onset of cannabis use, we identify a reverse directional effect, where adolescent cannabis use is associated with increased likelihood of future e-cigarette use.

Impacts of EU Tobacco Products Directive regulations on use of e-cigarettes in adolescents in Great Britain: a natural experiment evaluation

Background

E-cigarettes are a popular smoking-cessation tool. Although less harmful than tobacco, use of e-cigarettes by non-smokers should be prevented. There is concern about the use of e-cigarettes by young people and that e-cigarettes may renormalise smoking. In May 2016, Tobacco Products Directive regulations aimed to reduce e-cigarettes' appeal to young people.

Aims

To examine the effects of the Tobacco Products Directive regulations on young people's use of e-cigarettes, and the role of e-cigarettes in renormalising smoking.

Design

A mixed-method natural experimental evaluation combining secondary analyses of survey data, with process evaluation, including interviews with young people, policy stakeholders, retailers and trading standards observers, and observations of retail settings.

Settings

Wales, Scotland and England.

Participants

Survey participants were aged 13-15 years, living in England, Scotland or Wales and participated in routinely conducted surveys from 1998 to 2019. Process evaluation participants included 14- to 15-year-olds in England, Scotland and Wales, policy stakeholders, trading standards offices and retailers.

Intervention

Regulation of e-cigarettes, including bans on cross-border advertising, health warnings and restrictions on product strength.

Comparison group

Interrupted time series design, with baseline trends as the comparator.

Main outcome measures

The primary outcome was ever e-cigarette use. Secondary outcomes included regular use, ever and regular smoking, smoking attitudes, alcohol and cannabis use.

Data capture and analysis

Our primary statistical analysis used data from Wales, including 91,687 young people from the 2013-19 Health Behaviour in School-aged Children and School Health Research Network surveys. In Scotland, we used the Scottish Schools Adolescent Lifestyle and Substance Use Survey and in England we used the Smoking Drinking and Drug Use surveys. The process evaluation included interviews with 73 young people in 2017 and 148 young people in 2018, 12 policy stakeholders, 13 trading standards officers and 27 retailers. We observed 30 retail premises before and after implementation. Data were integrated using the Medical Research Council's process evaluation framework.

Results

Ever smoking continued to decline alongside the emergence of e-cigarettes, with a slight slowing in decline for regular use. Tobacco Products Directive regulations were described by stakeholders as well implemented, and observations indicated good compliance. Young people described e-cigarettes as a fad and indicated limited interaction with the components of the Tobacco Products Directive regulations. In primary statistical analyses in Wales [i.e. short (to 2017) and long term (to 2019)], growth in ever use of e-cigarettes prior to Tobacco Products Directive regulations did not continue after implementation. Change in trend was significant in long-term analysis, although of similar magnitude at both time points (odds ratio 0.96). Data from England and Scotland exhibited a similar pattern. Smoking followed the opposite pattern, declining prior to the Tobacco Products Directive regulations, but plateauing as growth in e-cigarette use stalled.

Limitations

Alternative causal explanations for changes cannot be ruled out because of the observational design.

Conclusions

Young people's ever and regular use of e-cigarettes appears to have peaked around the time of the Tobacco Products Directive regulations and may be declining. Although caution is needed in causal attributions, findings are consistent with an effect of regulations. Our analysis provides little evidence that e-cigarettes renormalise smoking. More recent data indicate that declines in smoking are plateauing.

Future work

International comparative work to understand differences in use of e-cigarettes, and tobacco, within varying regulatory frameworks is a priority.

Study registration

This study is registered as ResearchRegistry4336.

Funding

This project was funded by the National Institute for Health and Care Research (NIHR) Public Health Research programme and will be published in full in Public Health Research; Vol. 11, No. 5. See the NIHR Journals Library website for further project information.

A critique of the Australian National Health and Medical Research Council CEO statement on electronic cigarettes

This paper critically analyses a statement by Australia's National Health and Medical Research Council (NHMRC) on e-cigarettes in May 2022 that will be used to guide national policy. We reviewed the evidence and the conclusions drawn in the NHMRC Statement. In our view, the Statement is not a balanced reflection of the benefits and risks of vaping because it exaggerates the risks of vaping and fails to compare them to the far greater risks of smoking; it uncritically accepts evidence of harms from e-cigarettes while adopting a highly sceptical attitude towards evidence of their benefits; it incorrectly claims that the association between adolescent vaping and subsequent smoking is causal; and it understates the evidence of the benefits of e-cigarettes in assisting smokers to quit. The Statement dismisses the evidence that vaping is probably already having a positive net public health effect and misapplies the precautionary principle. Several sources of evidence supporting our assessment were published after the NHMRC Statement's publication and are also referenced. The NHMRC Statement on e-cigarettes does not present a balanced assessment of the available scientific literature and fails to meet the standard expected of a leading national scientific body.

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.

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

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

Electronic Cigarettes: A Pro-Con Review of the Current Literature

Electronic cigarettes (e-cigarettes, e-cigs, or electronic nicotine delivery systems) are battery-operated devices typically containing glycerol and/or propylene glycol-based solutions with varying nicotine content, known as e-liquids. Although e-cigarettes were originally developed as a potentially less harmful alternative to traditional combustible tobacco cigarette smokers, several factors have driven their popularity among smokers and nonsmokers alike, including their sleek product designs, innumerable appealing flavors, lack of combustible smoke and odor, and high potential nicotine concentrations. Furthermore, many advocates have promoted the idea that e-cigarettes are safe to use, or at least safer than conventional tobacco, despite limited longitudinal data to support these claims. Here, we examine what is known about the impacts of e-cigarette use on traditional cigarette smoking cessation, lung health, and youth and young adult tobacco product exposure. Upon review of the currently available literature, the negative effects of e-cigarette use seem to outweigh any potential benefit, because the available evidence does not confirm the use of e-cigarettes as an effective strategy for supporting traditional combustible tobacco cigarette smoking cessation, particularly given the emerging adverse effects on lung health and the potential future public health effects of e-cigarette adoption among a burgeoning new generation of tobacco product users.

Population-level counterfactual trend modelling to examine the relationship between smoking prevalence and e-cigarette use among US adults

BACKGROUND

Studies have suggested that some US adult smokers are switching away from smoking to e-cigarette use. Nationally representative data may reflect such changes in smoking by assessing trends in cigarette and e-cigarette prevalence. The objective of this study is to assess whether and how much smoking prevalence differs from expectations since the introduction of e-cigarettes.

METHODS

Annual estimates of smoking and e-cigarette use in US adults varying in age, race/ethnicity, and sex were derived from the National Health Interview Survey. Regression models were fitted to smoking prevalence trends before e-cigarettes became widely available (1999-2009) and trends were extrapolated to 2019 (counterfactual model). Smoking prevalence discrepancies, defined as the difference between projected and actual smoking prevalence from 2010 to 2019, were calculated, to evaluate whether actual smoking prevalence differed from those expected from counterfactual projections. The correlation between smoking discrepancies and e-cigarette use prevalence was investigated.

RESULTS

Actual overall smoking prevalence from 2010 to 2019 was significantly lower than counterfactual predictions. The discrepancy was significantly larger as e-cigarette use prevalence increased. In subgroup analyses, discrepancies in smoking prevalence were more pronounced for cohorts with greater e-cigarette use prevalence, namely adults ages 18-34, adult males, and non-Hispanic White adults.

CONCLUSION

Population-level data suggest that smoking prevalence has dropped faster than expected, in ways correlated with increased e-cigarette use. This population movement has potential public health implications.

Use of Electronic Cigarettes Among Cannabis-Naive Adolescents and Its Association With Future Cannabis Use

IMPORTANCE

Electronic cigarette (e-cigarette) use has been reported to increase the likelihood of future cigarette smoking among adolescents. The prospective association between e-cigarette use and cannabis use has been less clear, especially in recent years.

OBJECTIVE

To examine the association between e-cigarette use among cannabis-naive adolescents and cannabis use 1 year later.

DESIGN, SETTING, AND PARTICIPANTS

The Population Assessment of Tobacco and Health (PATH) Study, a nationally representative cohort study, uses a 4-stage, stratified probability sample design to select participants aged 12 years or older from the US civilian, noninstitutionalized population. This study sample included 9828 cannabis-naive adolescents at the baseline survey who participated in both wave 4.5 (2017-2018) and wave 5 (2018-2019) of PATH.

EXPOSURES

e-Cigarette use, assessed by ever use, past 12-month use, and past 30-day use.

MAIN OUTCOMES AND MEASURES

Cannabis use in wave 5, assessed by past 12-month and past 30-day use. Multivariable logistic regressions assessed the association between e-cigarette use and cannabis use 1 year later. Results were weighted to produce nationally representative findings.

RESULTS

Of the 9828 adolescents included in the analysis, 5361 (57.3%) were aged 12 to 14 years, 5056 (50.7%) were male, and 4481 (53.0%) were non-Hispanic White. After adjustment for sociodemographic characteristics, environmental factors, other substance use, and sensation seeking, e-cigarette use among cannabis-naive adolescents was associated with increased likelihoods of both self-reported past 12-month and past 30-day cannabis use 1 year later. The adjusted relative risks (aRRs) of subsequent past 12-month cannabis use with ever use of e-cigarettes was 2.57 (95% CI, 2.04-3.09), with past 12-month use of e-cigarettes was 2.62 (95% CI, 2.10-3.15), and with past 30-day use of e-cigarettes was 2.18 (95% CI, 1.50-2.85). The aRRs of subsequent past 30-day cannabis use with ever use of e-cigarettes was 3.20 (95% CI, 2.10-4.31), with past 12-month use of e-cigarettes was 3.40 (95% CI, 2.17-4.63), and with past 30-day use of e-cigarettes was 2.96 (95% CI, 1.52-4.40).

CONCLUSIONS AND RELEVANCE

This cohort study's findings suggest a strong association between adolescent e-cigarette use and subsequent cannabis use. However, despite the strong association at the individual level, e-cigarette use seems to have had a minimal association with the prevalence of youth cannabis use at the population level.