E-cigarettes are becoming increasingly popular among adolescents and the latest evidence suggests this can lead to adverse health effects in the future, and an increased risk of cardiovascular and pulmonary disease, said the American Heart Association in a scientific statement this week.
The statement, published in its journal Circulation Research, the said the toxicity of e-cigarettes “remains poorly understood, in part because most e-cigarette manufacturers have not publicly disclosed the full list of ingredients of the many e-cigarette products”.
“Since the exact composition of the products within the devices is not known, it is difficult to predict or determine the health effects on the lungs and heart. Other than nicotine, or THC, e-liquids contain vegetable glycerin and propylene glycol, which are on the US Food and Drug Administration’s (FDA) ‘generally regarded as safe’ (GRAS) list. However, these compounds were not intended to be inhaled, and therefore, have not been tested in a way to determine how inhaling them may affect a person.
“When heated, these compounds often break down into other chemicals such as formaldehyde, which is a known carcinogen.”
A scientific statement is an expert analysis of current research and may inform future clinical practice guidelines. In its statement, “Cardiopulmonary Consequences of Vaping in Adolescents”, experts in basic science, cellular and vascular biology, toxicology, pharmacology and epidemiology reviewed evidence-based studies focused on the cardiopulmonary effects of e-cigarette use in adolescents to inform on the short- and long-term risks of vaping and provide guidance to reduce vaping among adolescents.
“Most studies on the use of e-cigarettes have been conducted in adults or in animals,” said Loren Wold, Ph.D., FAHA, chair of the writing group for the scientific statement and a professor and associate dean for research operations and compliance in the College of Medicine at The Ohio State University in Columbus, Ohio.
“It’s critical we also understand how organ systems are affected in younger people who use e-cigarettes, and specifically, how these effects may persist into adulthood.”
Electronic nicotine delivery systems (ENDS) contain a battery, an atomiser (or heating element) and a reservoir for e-liquid in the form of cartridges, tanks or pods. These devices deliver an aerosol (usually containing nicotine or THC, the main psychoactive compound in cannabis) to the user that is inhaled into the lungs.
ENDS have been made to resemble pipes, hookah, cigars and cigarettes, with e-cigarettes being the most common. Among the latest iterations of e-cigarettes are devices that are small and often resemble a USB flash drive device. These devices contain e-liquids with high nicotine content in a salt form, combined with other chemicals.
Since e-cigarettes were introduced to the market in the early 2000s, their use has increased substantially, particularly among adolescents, reversing years of lower rates of tobacco use in youth and young adults and of declining nicotine dependency among users of standard, combustible cigarettes. In 2019, 27.5% of adolescents in grades 9-12 and 10.5% of younger adolescents in grades 6-8 reported vaping in the past month, according to the 2019 National Youth Tobacco Survey.
The Association’s scientific statement notes that although most new users of e-cigarettes have never smoked combustible cigarettes, adolescents who begin vaping now may become life-long nicotine or tobacco users and it is currently unknown what diseases may develop over a lifetime of vaping.
“Inhaling any foreign substance can have effects on the respiratory and cardiovascular systems,” Wold said. “Furthermore, a person’s lung development continues into the early 20s, so adolescents who vape are at risk of stunting or altering their lung development and may not reach full lung function.”
Previous studies have found that people who use e-cigarettes have an increased risk for respiratory health issues, including:
• higher rates of wheezing and cough;
• greater prevalence of asthma;
• increased susceptibility to pulmonary (lung) infections; and
• increased incidence of respiratory disease.
Additionally, studies have found that young adults who use e-cigarettes experience arterial stiffness, impaired blood vessel function, and increased blood pressure and heart rate. This evidence suggests that acute cardiovascular effects of e-cigarettes may accrue over time with prolonged use, leading to increased risk of cardiovascular disease in people who use e-cigarettes over the long-term.
“While adolescents who use e-cigarettes may not feel that vaping is affecting them at the moment, it is increasingly clear that the chemicals contained in e-cigarette aerosols are harming cardiovascular cells, leading to changes that promote the development of heart disease over time,” Wold said.
“It usually takes decades before people who smoke combustible cigarettes develop cardiovascular disease and/or chronic-obstructive pulmonary disease, and the same may be true of vaping. A reduction in adolescent vaping rates may help to improve long-term cardiopulmonary outcomes among this group.”
The statement writing committee noted that although the cardiopulmonary consequences of vaping are of central interest, vaping is already known to adversely affect important components of health. In particular, e-cigarette use impairs sleep quality, potentially affects mental health and leads to addiction through activation of certain brain pathways.
Studies have found that while some people may consider e-cigarettes as an aid to stop smoking combustible cigarettes, many people end up using both products regularly. The writing committee emphasised it is also important to distinguish between tobacco cessation and nicotine cessation.
One study from the United Kingdom, where the amount of nicotine in e-cigarettes is much lower than in the US, found e-cigarettes may be more effective than nicotine patches at combustible tobacco cessation (18% vs. 10%, respectively); however, the study found e-cigarettes were only 20% successful in reducing nicotine consumption compared to 81% effectiveness for nicotine patches.
“The customisability of e-cigarettes, including power levels, e-liquid content and the abundance of flavours, appeals to young people, and it also makes regulation of these products difficult,” Wold said.
“While the FDA has issued a policy against mint and fruit flavours of e-liquids that are known to appeal to youth, for some product types, menthol-flavoured products are still available. Additionally, there is no regulatory standard limiting the concentration of nicotine in e-liquids in the US. Some devices have been found to have nicotine levels of 59 mg/mL. In comparison, the European Union limits nicotine concentration in e-liquids to ≤20 mg/mL, which is comparable to the nicotine concentration in one standard combustible cigarette.”
The statement suggests the following for reducing or preventing youth vaping:
• Remove from the market all flavoured e-cigarettes, including menthol-flavoured e-cigarettes;
• Provide more education for youth and their parents regarding the confirmed and potential health risks of e-cigarette use;
• Establish vaping curricula for medical students to inform the next generation of health care professionals;
• Ensure hospital-based, vaping-cessation programmes for adolescents and adults;
• Regulate the marketing of e-cigarette products in traditional, online and social media platforms that are popular among youth; and
• Incorporate e-cigarettes into smoke-free air laws.
Study details
Cardiopulmonary Consequences of Vaping in Adolescents: A Scientific Statement From the American Heart Association
Loren Wold, Robert Tarran, Laura Crotty Alexander, Naomi Hamburg, Farrah Kheradmand, Gideon St. Helen, Joseph Wu.
Published in AHA Circulation Research on 21 June 2022
Abstract
Although the US Food and Drug Administration has not approved e-cigarettes as a cessation aid, industry has at times positioned their products in that way for adults trying to quit traditional cigarettes; however, their novelty and customisability have driven them into the hands of unintended users, particularly adolescents. Most new users of e-cigarette products have never smoked traditional cigarettes; therefore, understanding the respiratory and cardiovascular consequences of e-cigarette use has become of increasing interest to the research community.
Most studies have been performed on adult e-cigarette users, but the majority of these study participants are either former traditional smokers or smokers who have used e-cigarettes to switch from traditional smoking. Therefore, the respiratory and cardiovascular consequences in this population are not attributable to e-cigarette use alone.
Preclinical studies have been used to study the effects of naive e-cigarette use on various organ systems; however, almost all of these studies have used adult animals, which makes translation of health effects to adolescents problematic. Given that inhalation of any foreign substance can have effects on the respiratory and cardiovascular systems, a more holistic understanding of the pathways involved in toxicity could help to guide researchers to novel therapeutic treatment strategies.
The goals of this scientific statement are to provide salient background information on the cardiopulmonary consequences of e-cigarette use (vaping) in adolescents, to guide therapeutic and preventive strategies and future research directions, and to inform public policymakers on the risks, both short and long term, of vaping.
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