Abstract
Electronic cigarettes (e-cigarettes) and hookah smoking have gained tremendous popularity over the past decade. With the constantly evolving e-cigarette market and potential impact of the COVID-19 pandemic on users of these tobacco products, research is needed to assess the prevalence and safety of these devices as well as potential public health implications and cessation tools. For this year in review, PubMed was searched from January 2021–December 14, 2021, for articles related to e-cigarettes, vaping-related lung injury, and hookah smoking. Relevant articles addressing the objectives were included in this review. This review focused primarily on articles based on United States populations. Gray literature and nonpublished articles were not included in this review. The 2020 pandemic resulted in a decline in e-cigarette usage among youth (potentially due to the COVID-19 pandemic); however, recent research in 2021 suggests that e-cigarette usage is increasing again among youth. Conflicting evidence exists for e-cigarettes and the risk of COVID-19 infection, but biological plausibility suggests that e-cigarette users are more susceptible to COVID-19 infection and more severe COVID-19 infection compared to non–e-cigarette users. Hookah smoking has remained stable across the past several years and remains a primarily social activity among youth. New e-cigarette devices are constantly emerging, resulting in an increased demand to understand the safety of these devices. Additionally, hookah smoking continues to be a concerning public health issue with the increase in hookah bars and venues coupled with lack of policy regulations for hookah smoking
Introduction
Electronic cigarettes (e-cigarettes), vaping, and hookah have all gained tremendous attention in the past decade. E-cigarettes consist of cigarette-like devices that produce an aerosol mist, typically containing nicotine. E-cigarette usage is commonly referred to as vaping. Whereas e-cigarettes typically contain nicotine, vaping can refer to a broad category of liquids inserted in e-cigarette devices, including cannabinoids such as tetrahydrocannabinol. For the purpose of this paper, we are going to specifically focus on e-cigarettes and vaping related to nicotine. E-cigarettes are also commonly referred to as e-vaporizers, electronic nicotine delivery systems, and Juul.1
Hookah devices are water pipes used to smoke tobacco in various flavors. Hookah devices vary in size, shape, and style. Hookah smoking, sometimes referred to as waterpipe smoking, is typically done in social groups, usually sharing the same mouthpiece.2 Concerning trends have emerged for hookah smoking among young adults and college students alongside a surge of venues supporting indoor hookah smoking arriving around college campuses.
The purpose of this review is to (1) assess the literature in 2021 regarding e-cigarettes, vaping, and lung injuries, including the risk of COVID-19 infection in e-cigarette users; and (2) review the literature published in 2021 regarding hookah smoking as it relates to increased use among college-age students, lung injury, and long-term consequences.
Methods
PubMed was searched from January 2021–December 14, 2021, for articles related to e-cigarettes, vaping-related lung injury, and hookah smoking. E-cigarettes and vaping-related trends were searched using the terms “electronic cigarettes,” “e-cigarettes,” and “vaping.” Vaping-related lung injury papers were searched using the terms “vaping-related lung injury,” “vaping injury,” and “vaping pulmonary injury.” The research related to hookah smoking was searched using “hookah,” “waterpipe smoking,” and “hookah college.” Relevant articles addressing the objectives were included in this review. This review focused primarily on articles based on United States populations. Gray literature and nonpublished articles were not included in this review.
Brief History: E-Cigarettes
E-cigarettes were created in 2003 and internationally available in 2007.1 Whereas e-cigarettes were originally marketed as an alternative to traditional cigarettes, e-cigarettes quickly gained popularity among tobacco smokers and nonsmokers alike. Whereas adult usage of e-cigarettes has remained stable since 2010, the young adult population (ages 18–25) has experienced a surge in e-cigarette usage from 2012–2017.1 In 2012, the National Health Interview Survey reported that 2.4% of young adults used e-cigarettes in 2012, and 5.2% used e-cigarettes in 2015.1 Of particular concern, approximately 40% of e-cigarette users were never smokers before initiating e-cigarette use.1
Trends Among E-Cigarettes and Vaping in 2021
The prevalence of e-cigarettes has been steadily increasing among youth since e-cigarettes became widely available, specifically between years 2017–2019 (Fig. 1).3 However, e-cigarette usage declined among youth in 2020.4 This decline was likely a result of COVID-19 restrictions, as data from 2021 indicate usage is slightly increasing again with the relaxation of these restrictions.5 Approximately 11.3% of high school students and 2.8% of middle school students reported e-cigarette use in 2021.6 Additionally, nearly half of the high-school e-cigarette users reported using these e-cigarettes 20 or more days in the past 30 days (compared with 17.2% of middle-schooler e-cigarette users).6 Daily use was also prevalent among high-school (27.6%) and middle-school (8.3%) e-cigarette users. Among e-cigarette users, 85% reported using flavored e-cigarettes, which has implications for prevention and intervention strategies.6
Weighted percentages of past 30-day use of cigarette, electronic cigarette (e-cigarettes), and hookah devices among youth in the United States, Canada, and England from 2017–2019. Data from Reference 3.
Further evidence emerged over the last year linking e-cigarette use among youth with the initiation of marijuana and polysubstance use.7,8 Binge drinking and alcohol use were also strongly associated with e-cigarette use,9 with nondrinking e-cigarette users having a 3.5 times increased risk of initiating alcohol use in the following years compared to non–e-cigarette users.10 The co-occurrence of substance use associated with e-cigarette use is particularly concerning for the adolescent population because there is a lack of research on adverse health effects related to polysubstance use involving e-cigarettes.
Common misconceptions regarding e-cigarette use among youths continue to persist. For example, youths report that e-cigarettes are less harmful than traditional cigarettes.11 Additionally, disposable e-cigarettes have emerged on the market, complicating the public health battle to combat e-cigarette use.12 With the current e-cigarette market constantly evolving and changing, public health officials are faced with increasing barriers for preventing e-cigarette usage among youth. Whereas addressing the e-cigarette use epidemic among youth may seem daunting, individual-level and policy-level interventions have shown efficacy among preventing or decreasing e-cigarette use among youth. Specifically, statewide legislature restricting access to e-cigarettes among youths (or other regulations, including packaging restrictions, etc) has been associated with overall lower e-cigarette usage among youths.13 As of September 15, 2021, all 50 states have legislation restricting e-cigarette usage among youths (ranging from minimum age requirements for purchase from 18 years of age to 21 years of age).14 However, only 30 states (as of September 15, 2021) had legislation restricting product packaging for e-cigarettes.14
The FDA provided regulations on flavored e-cigarettes in 2020, banning flavored cartridges but allowing tobacco-flavored and menthol-flavored cartridges.15 Juul Labs also removed all mint-flavored products in 2019. Researchers found in 2021 that total e-cigarette sales declined following these regulations; however, mint-flavored e-cigarettes sales increased to 42.7% in the first 4-week period following the FDA guidance.15
The FDA approved marketing of 3 new devices from R.J. Reynolds Vapor Company in October 2021.16 These 3 e-cigarette products were cited by the FDA as reducing traditional cigarette usage among adults, allowing for a pathway to tobacco cessation altogether. However, the usage of e-cigarettes for tobacco and smoking cessation is heavily debated among researchers, public health experts, and medical professionals.17
E-Cigarettes: Successful Aid to Smoking Cessation?
Whereas e-cigarettes were traditionally created as an alternative to traditional cigarettes, the debate over whether e-cigarettes are a useful smoking cessation tool is ongoing. However, more researchers are concluding that e-cigarettes are not a helpful or useful smoking cessation tool, and e-cigarette usage alongside traditional cigarette usage inflicts more harm than good.17 Ibrahim and colleagues published a meta-analysis in 2021 concluding that very weak evidence supports e-cigarettes as a smoking cessation tool in the short term, but there lacks substantial evidence of the long-term effects of e-cigarettes.17 Among the 12 trials, e-cigarettes improved 1-month abstinence levels by 33% (ranging from 6–66%).17 However, there was not sufficient evidence to support abstinence levels at 3- and 6-month follow-up periods. Therefore, there is currently not enough evidence to recommend e-cigarettes as a safe and efficacious cessation tool, which has tremendous implications for current health care providers.17 The World Health Organization advises against using e-cigarettes as smoking cessation aids, citing that other pharmacologic and nonpharmacologic treatments are safer and efficacious alternatives.18
E-Cigarette Toxicity
Since the e-cigarette market is rapidly changing and evolving, researchers are constantly evaluating the new products to determine toxicity levels. In 2021, e-cigarette users produced similar amounts of cotinine, a metabolite of nicotine, as traditional cigarette users, emphasizing that nicotine concentrations in e-cigarettes are comparable to traditional cigarettes.19 E-cigarette users also exhibited the same toxins as traditional cigarette users, including lead levels, volatile organic compounds, benzene, cyanide, and other heavy metals.19 Another 2021 review showed vitamin E acetate toxicity as the primary cause of the e-cigarette or vaping product use-associated lung injury (EVALI) outbreak in 2019.20 However, more human studies are needed to determine the concentrations of vitamin E acetate that are toxic to humans and the toxicity impact of vitamin E acetate alongside other compounds.20
E-Cigarette-Related Adverse Health Effects
EVALI was a major public health epidemic in the United States in fall 2019. This outbreak was eventually linked to vitamin E acetate, implicated in homemade or e-cigarette liquids obtained from informal sources.20 There were approximately 2,800 cases of EVALI and 50 deaths among 50 states.20,21 Researchers have been studying the broad effects of e-cigarettes on the pulmonary system, including the systemic effects of e-cigarettes.
In 2021, Wills and colleagues published an integrative review of respiratory disorders associated with e-cigarette use.22 Epidemiological studies showed e-cigarette usage was associated with asthma (15 studies) and COPD (9 studies). Laboratory studies supported the biological plausibility of these findings, showing that e-cigarettes were more harmful than controls to the respiratory system.22 Self-reported respiratory symptoms are more prevalent among e-cigarette users compared to non-users.23,24 These symptoms included wheezing, phlegm production, and coughing.23,24 Dual users of e-cigarettes and traditional cigarettes had the highest prevalence of self-reported respiratory symptoms.23 E-cigarette use was also more prevalent among those with chronic lung disease in another study.9 Cardiovascular disease also remains a concern among e-cigarette users, similar to traditional cigarette users, due to the nicotine and particulate matter contained in e-cigarettes.25 The long-term effects of e-cigarettes are still to be determined, but recent research is clear that strong links that exist between e-cigarettes and adverse health effects.
The acute effects of e-cigarettes are also important to study. McClelland and colleagues published an article in Respiratory Care in 2021 examining the acute effects of vaping.26 Vaping was associated with experiencing elevated heart rate, breathing frequency, temperature (oral), and lower blood oxygenation levels. However, blood sugar and FVC were not acutely affected by vaping.26
Risk of COVID-19 Infection Among E-Cigarette Users
In 2020, e-cigarette users were nearly 5 times more likely to acquire COVID-19 infection compared to non-users,27 and dual users of e-cigarettes and traditional cigarette users were 6.8 times more likely to acquire COVID-19.27 It’s unsurprising that pulmonary immunity is compromised by e-cigarette use since they are implicated in the EVALI outbreaks of 2019. Biological mechanisms linking e-cigarette use to increased susceptibility to COVID-19 also include alteration in pulmonary defense mechanisms, upregulation of ACE2 inhibitors, and oxidative stress.28 Laboratory findings have also shown that flavoring compounds in e-cigarettes exert a suppressive effect on the inflammatory cytokines among human bronchial epithelial cells.29 Biological plausibility exists for e-cigarette users experiencing more severe forms of COVID-19, supported by the impact of vaping on neutrophils and the strong association between neutrophils facilitating acute lung injury in COVID-19.30
Conflicting findings emerged in 2021 related to e-cigarette users and COVID-19 susceptibility. Duszynski and colleagues found an association between COVID-19 and nicotine, but this association was not found among exclusive e-cigarette users (users who did not use other tobacco products).31 Another 2021 study showed that e-cigarette users were not at an increased risk for COVID-19 compared to non–e-cigarette users.32 Jose et al collected data using an electronic health record database, which may be subject to underreporting bias of e-cigarette usage among patients.32 Duszynski and colleagues examined laboratory-confirmed COVID-19 diagnoses and a health assessment questionnaire.31
A confusion of differential diagnoses emerged in the pediatric population between multisystem inflammatory syndrome in children (MIS-C) and EVALI during the COVID-19 pandemic.33 A case series in 2021 documented several cases that were initially thought to be MIS-C but were eventually diagnosed as EVALI. Providers recommended COVID-19 tests to make the differentiation, along with social history obtained from peers and parents regarding e-cigarette usage.33
Hookah Smoking: Trends in 2021
As mentioned previously, hookahs are defined as water pipes used to smoke tobacco in various flavors.2 Hookah devices can come in many sizes, shapes, and styles, and the practice of hookah smoking is typically performed in groups at places like hookah bars. Hookah smoking remained constant between 2017–2019 among youths in the United States.3 Many youths who smoke hookah also smoke other tobacco products, including traditional cigarettes.3 Youths state they enjoy the socialization aspect of hookah smoking, which is hypothesized as the main driver of hookah smoking for youths.34 Adults and youths who engaged in hookah smoking also stated that availability of flavored hookah and the affordability of hookah were factors associated with increased hookah use and reduced hookah cessation.35
Hookah-Related Adverse Health Effects
Similar to e-cigarettes and traditional cigarettes, hookah smoke contains toxic elements, including heavy metals, carbon monoxide, nicotine, and flavorants.36 Whereas one study in 2021 demonstrated that nicotine levels are less in hookah smoke compared to e-cigarettes, there is comparable exposure to nicotine levels for both hookah smokers and e-cigarette users based on differential consumption levels.37 For example, one hookah session might result in 100 puffs, whereas e-cigarette users might smoke 10 puffs per independent session with multiple sessions daily.37
The acute effects of hookah smoking are also of concern. An article published in respiratory care showed hookah smokers had an increased heart rate, reduced perfusion index, and increased carbon monoxide levels after visiting hookah bars.38 These differences were all found to be statistically significant.38 Acute effects of hookah smoking (both flavored and nonflavored) were also found to increase urinary biomarkers of DNA and RNA oxidative stress.39 Research emerged in 2021 showing hookah initiation is most common between ages 18–19.40 Whereas the long-term effects of hookah smoking have yet to be determined, evidence is concerning for increased risk for pulmonary and cardiovascular disease long term.
A new device categorized as hookah smoking is called the e-hookah, which consists of a traditional water pipe with aerosol passing through a water-filled base before being inhaled.41 Researchers have begun to study differences between e-hookahs and traditional hookah smoking. Concerningly, e-hookahs led to a larger increase in carotid-femoral pulse wave velocity (associated with larger arterial stiffening) compared to traditional hookah smoking, indicating large arterial stiffening.41 Researchers also found that both types of hookah smoking led to increases in C-reactive protein, fibrinogen, and tumor necrosis factor α after use.41
In 2016, the FDA extended authority to cover all tobacco products but delayed their oversight on hookah products to 2021. Therefore, there is no current oversight for hookah use.42 However, several interventions address hookah use among youths and young adults, including the Tobacco Prevention Toolkit.43
Summary
A recent commentary emphasized the urgent need for stronger tobacco control policies, particularly for alternative tobacco products such as e-cigarettes and hookah.44 Research on policies related to traditional cigarettes shows the strong link between taxation, strict policies, and reduced traditional cigarette usage. These findings can be extrapolated to alternative tobacco products, such as e-cigarettes and hookah. Regulations on e-cigarette marketing can be strengthened, with only 30 states currently restricting packaging on e-cigarettes. Moreover, hookah smoking lacks regulation from the FDA, and current policies are poorly enforced. Hookah smoking is often taxed at a lower rate than traditional cigarettes, which is problematic for accessibility among youths. However, some areas have strengthened policies related to hookah smoking. For example, San Francisco and Minneapolis have prohibited flavored tobacco products, including hookah. College students are particularly vulnerable due to the prime age of alternative tobacco product initiation. Additionally, the COVID-19 pandemic raises serious concerns about vulnerability to infection for e-cigarette and hookah users. Whereas the current evidence is conflicting regarding the susceptibility of e-cigarette users for COVID-19 infection, biological plausibility exists for e-cigarette users having both increased risk of infection and increased severity of COVID-19 infection compared to non-users.31 Multi-level interventions are needed for both youth and adults regarding e-cigarette and hookah use, including policy-level, interpersonal and community-level, and individual-level behavioral interventions.44
Footnotes
- Correspondence: Rachel E Culbreth PhD MPH RRT, Georgia State University, 140 Decatur Street, Atlanta, Georgia, 30302. Email: rculbreth{at}gsu.edu
Dr Culbreth discloses a relationship with CAIRE. The other authors have disclosed no conflicts of interest.
Parts of this manuscript were presented at the AARC Congress 2021 LIVE!, held virtually December 1, 3, 7, and 9, 2021.
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