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Teens who use e-cigarettes more apt to start smoking, study says

Two new studies of e-cigarettes may bolster US government efforts to stem what it calls a growing epidemic of youth vaping, writes Anna Edney for Bloomberg. Children and teens who had used e-cigarettes were four times more likely to have taken up cigarette smoking than those who didn’t vape, says one study published in the Journal of the American Medical Association.

Almost 179,000 youth who have tried cigarettes and more than 43,000 who are currently smoking would not be if they had never started vaping, the study found.

The link between vaping and cigarette use was particularly pronounced in those thought to be low-risk for smoking given their lack of prior drug and alcohol use, according to the study.

That raises the concern “that e-cigarettes may renormalize smoking behaviors and erode decades of progress in reducing smoking among youths,” the study’s authors wrote.

“These findings strengthen the rationale for aggressive regulation of youth access to and marketing of e-cigarettes to achieve future decreases in the prevalence of cigarette use among youths,” they said.

The JAMA study analyzed data on 6,123 youth collected by the National Institutes of Health and the US Food and Drug Administration from 2013 to 2016.

‘Not risk-free’

The report was released on the same day, 1 February 2019, as a separate study by the Harvard TH Chan School of Public Health that found common e-cigarette flavors may harm users’ lungs. The findings may deal a blow to the vaping industry, which has come under fire by the FDA for allegedly marketing to teenagers by using fruit flavors.

Philip Morris International Inc, whose sister company Altria Inc is seeking FDA approval to sell its “heat-not-burn” IQOS tobacco device, said a balance must be struck between seeking to prevent teens from using nicotine products and helping to move adult smokers away from cigarettes.

“Nicotine is addictive. It is not risk-free, and it poses particular risks for adolescents,” said PMI spokesman Corey Henry. He said the company won’t offer its smoke-free products to people who have never smoked or those who have quit smoking.

FDA Commissioner Scott Gottlieb proposed measures in November for restricting sales of most flavored e-cigarettes and limiting them to specialized shops and online retailers that can verify a purchaser’s age. That was a reversal of a hands-off approach to e-cigarettes Gottlieb took in 2017, which was followed by a 75 percent rise between 2017 and 2018 in use of e-cigarettes by children and teens.

In 2017, more than two million middle- and high-school students used e-cigarettes, according to the Centers for Disease Control and Prevention.

The Harvard study published in Scientific Reportsdetermined that two chemicals commonly used to flavor e-cigarettes may be harming the cilia, the antennae-like protrusions that line human airways to help keep them clean.

The study examined diacetyl, which has previously been linked to an illness known as “popcorn lung” in workers in factories that make microwave popcorn, and an alternative called 2,3-pentanedione.

Those chemicals haven’t been tested for inhalation safety, said senior co-author Joseph Allen, assistant professor of exposure assessment science at Harvard.

“Although some e-cig manufacturers are stating that they do not use diacetyl or 2,3-pentandione, it begs an important question: What chemicals, then, are they using for flavoring?” Allen said in a statement.

Juul Labs Inc, the vaping market leader whose devices are wildly popular with teens, says on its website that “our development and manufacturing process does not add diacetyl and acetylproprionyl (or 2,3-pentanedione) as flavor ingredients.”

study published earlier this week in the New England Journal of Medicinefound e-cigarettes are almost twice as effective at helping cigarette smokers quit as other nicotine-replacement therapies. Gottlieb has maintained that e-cigarettes could be a valuable tool to help adult smokers quit, but tweeted Thursday that children and teens are still his priority.


Association of Electronic Cigarette Use With Subsequent Initiation of Tobacco Cigarettes in US Youths


Kaitlyn M Berry, Jessica L Fetterman and Emelia J Benjamin et al.


Is electronic cigarette (e-cigarette) use among tobacco-naive youths associated with subsequent risk of cigarette initiation?


In this cohort study using data from the Population Assessment of Tobacco and Health Study (2013-2016), youths whose first tobacco product was an e-cigarette were more likely to initiate cigarettes over 2 years of follow-up.

At the population level, approximately 180 000 new ever smokers and 45 000 current smokers in the United States over 2 years may have started smoking combustible cigarettes after initiating e-cigarette use.


Tobacco-naive youths who initiate e-cigarettes may be at greater risk of subsequently initiating cigarette smoking.


The use of electronic cigarettes (e-cigarettes) and other noncigarette tobacco products may increase the odds of cigarette initiation, even among low-risk youths.


To evaluate the associations of prior e-cigarette use and other tobacco product use with subsequent cigarette initiation within 2 years of follow-up.

Design, Setting and Participants

In this prospective cohort study, data from waves 1 through 3 of the Population Assessment of Tobacco and Health Study (2013-2016) were used to assess youths aged 12 to 15 years who had never used cigarettes, e-cigarettes, or other tobacco products at wave 1. This was a nationally representative study of the US population. Data analysis was conducted in 2018.


First noncigarette tobacco product used (none, e-cigarette, or other tobacco product) between wave 1 and wave 3.

Main outcomes and measures  

Ever cigarette use and current cigarette use at wave 3.


In the sample (N = 6123), respondents were 49.5% female; 54.1% non-Hispanic, white; and the mean (SD) age was 13.4 (1.2) years. Of these, 8.6% reported e-cigarettes as their first tobacco product, while 5.0% reported using another noncigarette product first; 3.3% reported using cigarettes first.

Cigarette use at wave 3 was higher among prior e-cigarette users (20.5%) compared with youths with no prior tobacco use (3.8%). Prior e-cigarette use was associated with more than 4 times the odds of ever cigarette use (odds ratio, 4.09; 95% CI, 2.97-5.63) and nearly 3 times the odds of current cigarette use (odds ratio, 2.75; 95% CI, 1.60-4.73) compared with no prior tobacco use.

Prior use of other tobacco products was similarly associated with subsequent ever cigarette use (OR, 3.84; 95% CI, 2.63-5.63) and current cigarette use (OR, 3.43; 95% CI, 1.88-6.26) compared with no prior tobacco use. The association of prior e-cigarette use with cigarette initiation was stronger among low-risk youths (OR, 8.57; 95% CI, 3.87-18.97), a pattern not seen for prior other product use.

Over the 2 years between 2013 and 2014 and 2015 and 2016, 21.8% of new cigarette ever use (178 850 youths) and 15.3% of current cigarette use (43 446 youths) among US youths aged 12 to 15 years may be attributable to prior e-cigarette use.

Conclusions and relevance  

This study’s findings support the notion that e-cigarette use is associated with increased risk for cigarette initiation and use, particularly among low-risk youths. At the population level, the use of e-cigarettes may be a contributor to the initiation of cigarette smoking among youths.


Common e-cigarette chemical flavorings may impair lung function

Two chemicals widely used to flavor electronic cigarettes may be impairing the function of cilia in the human airway, according to a new study led by Harvard TH Chan School of Public Health.

Cilia are antennae-like protuberances that are present on 50-75% of the cells that line human airways. They play a key role in keeping the human airway clear of mucus and dirt and allow people to breathe easily and without irritation. Impaired cilia function has been linked with lung diseases such as chronic obstructive pulmonary disease (COPD) and asthma.

“Although chemicals used to flavor e-cigs are frequently used, little has been known about the mechanism of how they impact health. Our new study suggests that these chemicals may be harming cilia – the first line of defense in the lungs – by altering gene expression related to cilia production and function,” said Quan Lu, associate professor of environmental genetics and pathophysiology. Lu and Joseph Allen, assistant professor of exposure assessment science, were co-senior authors of the study.

The study was published on 1 February 2019 in Scientific Reports. It is the first to look at the impact of flavoring chemicals in human epithelial cells, which are the type that line the lungs.

Millions of people use e-cigarettes, and a recent rise in use among school-aged children has alarmed public health experts. In mid-December, US Surgeon General Jerome Adams labeled youth e-cigarette use an epidemic. Scientific studies examining the potential health effects of e-cigarettes and their myriad chemical components have not kept pace with the rise in use.

In a previous study, Allen and Harvard Chan colleagues found flavoring chemicals – primarily diacetyl and 2,3-pentanedione – in over 90% of e-cigarettes they tested.

In addition to being used in e-cigarettes, diacetyl is used as a flavoring agent in foods such as butter-flavored microwave popcorn, baked goods, and candy; it can create a variety of flavors.

Diacetyl is considered a safe ingredient in foods, but evidence suggests that it can be dangerous when inhaled. It has been previously linked with bronchiolitis obliterans, a debilitating lung disease that was dubbed “popcorn lung” because it first appeared in workers who inhaled artificial butter flavor in microwave popcorn processing facilities. After the link between diacetyl and popcorn lung was reported, 2,3-pentanedione was sometimes used as a substitute.

In the new study, researchers used novel lab techniques that allowed them to examine the impact of both diacetyl and 2,3-pentanedione on epithelial cells in a system that closely mimicked the human airway epithelium in vivo.

They exposed normal human bronchial epithelial (NHBE) cells to the chemicals for 24 hours. They found that both diacetyl and 2,3-pentanedione were linked with changes in gene expression that could impair both the production and function of cilia.

In addition, the researchers found that even low levels of both chemicals affected gene expression, suggesting that current standards for safe limits of exposure to these chemicals for workers may not be sufficient. There are no such standards for e-cigarette users, according to the authors.

“E-cigarette users are heating and inhaling flavoring chemicals that were never tested for inhalation safety,” said Allen. “Although some e-cig manufacturers are stating that they do not use diacetyl or 2,3-pentandione, it begs an important question – what chemicals, then, are they using for flavoring? Further, workers receive warnings about the dangers of inhaling flavoring chemicals. Why aren’t e-cig users receiving the same warnings?”

Other Harvard Chan authors of the study included lead author Hae-Ryung Park, Michael O’Sullivan, Jose Vallarino, Jin-Ah Park, and David Christiani.

Funding for the study came from National Institutes of Health (NIH)/National Institute of Environmental Health Science (NIEHS) R01 grant ES022230 and the Harvard NIEHS Center grant (P30ES000002).

“Transcriptomic response of primary human airway epithelial cells to flavoring chemicals in electronic cigarettes” is authored by Hae-Ryung Park, Michael O’Sullivan, Jose Vallarino, Maya Shumyatcher, Blanca E. Himes, Jin-Ah Park, David C. Christiani, Joseph Allen, and Quan Lu.


[link url=""]Teens Who Use E-Cigarettes More Apt to Start Smoking, Study Says[/link]

[link url=""]Association of Electronic Cigarette Use With Subsequent Initiation of Tobacco Cigarettes in US Youths[/link]

[link url=""]Common e-cigarette chemical flavorings may impair lung function[/link]


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