A recent study in the United States, published in the American Heart Association journal Circulation, suggests that vaping is much less harmful than smoking. The authors and the journal tried to minimise this result. Do they have an anti-vaping bias? Asks Cameron English of the American Council on Science and Health (ACSH).
The following article was published by on 10 May 2022 by the ACSH, a non-profit pro-science consumer advocacy organisation that aims to “support evidence-based science and medicine and to debunk junk science and exaggerated health scares”. Below it is a press release from the American Heart Association (AHA), followed by the research letter published in Circulation.
Anti-vaping bias undermines e-cigarette research?
Inexperienced journalists commonly make a mistake known as ‘burying the lede’, or hiding the most crucial aspects of a story underneath lots of distracting and less significant information. Scientists often make an analogous mistake, by emphasising less important results from their research while minimising others that are more relevant, especially because they're related to public health.
Case in point: a study published in the American Heart Association journal Circulation reported an association between dual use of e-cigarettes and combustible tobacco and increased cardiovascular disease (CVD) risk over a six-year period.
The paper's results, as we'll see, clearly support vaping as a low-risk alternative to smoking, but the AHA did its best to downplay this result.
The study
The researchers surveyed 24,027 participants from the Population Assessment of Tobacco and Health (PATH) study, who self-reported their smoking, vaping, or dual-use habits annually between 2013 and 2019.
Anyone who had smoked more than 100 cigarettes in their lifetime and reported current smoking was classified as a smoker. If someone reported any current e-cigarette use, they were categorised as a vaper. Participants were classified by “non-use (no current e-cigarette use or smoking), exclusive e-cigarette use, exclusive smoking, or dual use”. These classifications were updated annually.
The researchers defined incident CVD as any self-reported diagnosis of myocardial infarction (MI) or bypass surgery, heart failure (HF), other heart condition, or stroke starting at wave 2 and continuing through to wave 5; they also measured MI, HF and stroke separately.
What they should have led with
Setting aside the broad exposure definitions utilised in this study, which I've criticised previously, the results painted vaping in a rather favourable light:
“After adjusting for covariates, participants exclusively using e-cigarettes had risk of developing any CVD condition that did not differ from non-users and higher, albeit non-significant, risk of the MI, HF, or stroke outcome … Compared with smoking, e-cigarette use was associated with 30% to 40% lower CVD risk, although this association was only significant for the any CVD outcome.”
Smokers self-reported 569 CVD events compared to just 41 in e-cigarette users. Limiting the results to heart attack, heart failure, or stroke, smokers experienced 242 events, but vapers reported only 15 of these same events.
That's a tremendous risk reduction, so the obvious conclusion to draw from these results is that vaping is associated with far less CVD than smoking.
Depending on the specific condition under observation, it appears that vaping poses very little risk whatsoever.
But it gets better. The authors went on to note that: “We did not find a significant difference in the cardiovascular risk of exclusive e-cigarette use compared with non-use of cigarettes and e-cigarettes, although analyses were limited by a small number of CVD events in e-cigarette users.”
Read that sentence again. They couldn't determine if the cardiovascular risk of vaping was statistically significant because e-cigarette users experienced too few CVD events. In other words, there was no meaningful association between vaping and increased cardiovascular disease risk.
That's the take-home message of this paper. Yet, this is the headline the American Heart Association put on its press release for the study: “No health benefits among adults who used both e-cigarettes and traditional cigarettes”.
Even here, though, the results weren't clear. It's possible that the elevated CVD risk of dual-users was attributable entirely to their cigarette consumption. For instance, if someone smoked two fewer cigarettes daily out of a pack of 20, they still smoked 18 cigarettes every day for six years.
We don't know if that's what actually happened; the exposure data is too vague to draw such a specific conclusion. But the fact remains: the AHA highlighted the only result that portrays vaping as harmful.
Inconvenient results
I suspect the AHA knows how bad these results look for the campaign against e-cigarettes, because the press release included this very revealing quote:
“While the PATH study is providing essential longitudinal data on the use of traditional and e-cigarettes, as well as on outcomes such as cardiovascular events, the data are self-reported, the study duration is short and the event rate is still low – especially in younger people.
“Since e-cigarette use is still relatively new, there is not yet a strong body of long-term evidence to determine the eventual risk of using these products over time … It’s important to remember that even with traditional cigarettes, decades of use and surveillance were needed to provide the strength of evidence we now have confirming the highly significant harm of combustible cigarettes.”
– Dr Rose Marie Robertson, deputy chief science and medical officer of the American Heart Association
These comments prompt several questions.
Almost every epidemiological study has some important flaws or limitations. You usually have to read the paper very carefully to uncover those deficits, but the AHA is offering them up in the press release – the document that gullible journalists use to write their stories.
Why did the AHA so eagerly highlight PATH's self-reported data, low event rate, and short duration? Moreover, if the PATH results are so incomplete, why did these researchers use them in the first place?
Finally, why did Robertson imply that future studies may uncover serious vaping-related health risks as earlier research did for tobacco use? We already know that vaping is much less harmful than smoking, so her analogy is unjustified.
The long-term risks of any new product are, by definition, unknown. Yet, we shouldn't speculate about what those risks could be, especially when the existing data suggest that the product isn't very harmful.
By way of comparison, no respectable scientist would warn that: “Since COVID vaccination is still relatively new, there is not yet a strong body of long-term evidence to determine the eventual risk of receiving these immunisations over time.”
People who speculate in this manner are quickly labelled anti-vaccine quacks. But tobacco-control researchers make the same illogical leap when trying to tap dance around the evidence on e-cigarettes. They need to stop.
A growing body of research, arguably including the present study, shows that vaping is a safer alternative to smoking. Until the data show otherwise, let's stick with that conclusion.
American Heart Association release
Smoking both traditional and e-cigarettes may carry same heart risks as cigarettes alone
Published on 6 May 2022.
Smokers who think they can lower their risk for cardiovascular disease by sometimes smoking e-cigarettes instead of traditional ones might need to think again. A new study finds people who use both have the same cardiovascular disease risks as those who only smoke traditional cigarettes.
“The fact that dual use – using both traditional, combustible cigarettes and e-cigarettes – had similar cardiovascular disease risk to smoking cigarettes only is an important finding as many Americans are taking up e-cigarettes in an attempt to reduce smoking for what they perceive is a lower risk,” senior study author Dr Andrew Stokes said in a news release.
Stokes is an assistant professor in the department of global health at Boston University School of Public Health. “It is common for people to try to switch from traditional cigarettes to e-cigarettes and get caught in limbo using both products,” he said.
Cigarette smoking and second-hand smoke exposure are responsible for nearly one in five deaths in the US each year, according to American Heart Association statistics.
In addition to heart disease and stroke, traditional cigarette smoking causes a wide range of health issues, including cancer and lung diseases. E-cigarettes contain many toxic chemicals, but how their long-term use affects heart health has not been well-studied.
The study, published in the American Heart Association journal Circulation, used data from the Population Assessment of Tobacco and Health study, which collected information on health and nicotine use from 2013 to 2019.
Researchers compared cardiovascular health for 24,027 traditional cigarette smokers, e-cigarette smokers and people who used both products. Nearly 1,500 cardiovascular events – heart attacks, bypass surgery, heart failure, stroke or other heart condition – were self-reported.
Researchers found no significant differences in heart attacks, heart failure or strokes among people who smoked a combination of traditional cigarettes and e-cigarettes, compared to those who smoked traditional cigarettes only.
Those who exclusively used e-cigarettes were 30% to 40% less likely to report cardiovascular disease events; however, the number of heart-related events was too small for researchers to draw any solid conclusions.
While the study provides important information on the use of e-cigarettes and their impact on cardiovascular health, it relies on self-reported data over a short period of time “and the event rate is still low – especially in younger people”, Dr Rose Marie Robertson said in the release. She is co-director of the AHA's Tobacco Center of Regulatory Science, which supported the study.
Because e-cigarettes are still relatively new, there is still a need for more data and ongoing research to create a strong body of evidence on their long-term risks, she said.
“It's important to remember that even with traditional cigarettes, decades of use and surveillance were needed to provide the strength of evidence we now have confirming the highly significant harm of combustible cigarettes. People should know that e-cigarettes contain addictive nicotine and toxic chemicals that may have adverse effects on their cardiovascular system and their overall health.”
While that research continues, Stokes said people trying to quit should not move to e-cigarettes as a solution.
“Many smokers who attempt to use e-cigarettes for traditional cigarette smoking cessation actually continue using both products, becoming dual users, where we saw no reduction in cardiovascular risk,” he said.
“We are concerned that any recommendation of e-cigarette use for smoking cessation may lead to increased dual use, as well as e-cigarette initiation among young adults and those who have never smoked cigarettes.”
Experts say people interested in quitting should speak with their health care team about Food and Drug Administration-approved options.
Study details
Cigarette Use and Risk of Cardiovascular Disease: A Longitudinal Analysis of the PATH Study (2013–2019)
Jonathan B Berlowitz, Wubin Xie, Alyssa F Harlow, Naomi M Hamburg, Michael J Blaha, Aruni Bhatnagar, Emelia J Benjamin and Andrew C Stokes.
Author affiliations: Boston University, University of Southern California, Ciccarone Center for the Prevention of Cardiovascular Disease, Johns Hopkins and University of Louisville.
Published in Circulation on 6 May 2022.
Research Letter
Despite increasing popularity of electronic cigarettes (e-cigarettes), the long-term health effects of habitual e-cigarette use remain unclear. Many constituents of e-cigarette aerosols, including nicotine, carbonyl compounds, fine particulate matter, and metals, are associated with substantial toxicity. Inhalation of e-cigarette aerosols among young, healthy adults induces inflammation and oxidative stress.
Two large cross-sectional studies reported no significant association between exclusive e-cigarette use and cardiovascular disease (CVD). However, longitudinal studies are essential to assess the association of e-cigarette use with incident CVD.
Data came from the PATH study (Population Assessment of Tobacco and Health), a nationally representative cohort study with five annual waves of self-reported data collected from 2013 to 2019.
The initial sample included 32,320 non-institutionalised US adults aged 18 years or older with oversampling of tobacco users, young adults, and African American individuals.
Excluded respondents included those lost to follow-up at wave two (5,873), previously diagnosed with CVD (2,172), or missing baseline exposure (55), baseline CVD (99), or wave two outcome data (94).
Participants were considered smokers if they smoked >100 cigarettes in their lifetime and reported current cigarette smoking; participants were considered e-cigarette users if they reported any current e-cigarette use. Participants were classified into non-use (no current e-cigarette use or smoking), exclusive e-cigarette use, exclusive smoking, or dual use. Exposures were updated at each wave of follow-up.
Incident CVD was defined as any self-reported past 12-month diagnosis of myocardial infarction (MI) or bypass surgery, heart failure (HF), other heart condition, or stroke over waves 2 to 5, with a separate outcome only including MI, HF, and stroke. The validity and reliability of self-reported MI, HF and stroke were supported previously within the PATH study sample.
Cox regressions were used to model incident composite CVD outcomes as a function of a 4-category cigarette and e-cigarette use exposure measure. Respondents contributed a maximum of four years of follow-up time from baseline (wave 1) until a CVD diagnosis, loss to follow-up, or the end of follow-up (wave 5), whichever came first.
Multiple imputation was used to account for missing covariate data and wave 2 longitudinal weights were incorporated to generate nationally representative estimates. The analytic code is available on request to reproduce the results.
Analyses were adjusted for baseline covariates potentially associated with tobacco use and CVD, including age (18–24, 25–34, 35–44, 45–54, 55–64, 65–74, 75+ years), sex, race and ethnicity (Hispanic, non-Hispanic Black, non-Hispanic White, non-Hispanic other), education (less than high school, high school/General Equivalency Development, some college, bachelor degree or above), body mass index, hypertension, high cholesterol, diabetes and family history of MI.
Analyses were also adjusted for ever use of marijuana, cigarette pack-years, and pack-years squared. Adjustment for time-varying current use of noncigarette combustible (hookah, pipe, cigar, cigarillo) and non-combustible (snus, other smoke-less) tobacco were also included.
There were 24,027 eligible respondents (50% younger than 35 years, 51% women). Exclusive e-cigarette users and dual users, as compared with non-users, were younger (62% and 54% younger than 35 years, respectively, versus 51%) and had accumulated more cigarette pack-years (11.0±46.7 and 15.7±32.2, respectively, versus 4.2±21.8). There were 1,487 incident cases of any CVD and 519 cases of MI, HF, or stroke.
After adjusting for covariates, participants exclusively using e-cigarettes had risk of developing any CVD condition that did not differ from non-users and higher, albeit non-significant, risk of the MI, HF, or stroke outcome (hazard ratio [HR], 1.00 [95% CI, 0.69–1.45] and HR, 1.35 [95% CI, 0.75–2.42], respectively).
Compared with smoking, e-cigarette use was associated with 30% to 40% lower CVD risk, although this association was only significant for the any CVD outcome. Dual users had risk that did not differ from exclusive smokers for the any CVD and MI, HF, or stroke outcomes (HR, 1.01 [95% CI, 0.81–1.26] and HR, 0.94 [95% CI, 0.65–1.36], respectively).
We did not find a significant difference in the cardiovascular risk of exclusive e-cigarette use compared with non-use of cigarettes and e-cigarettes, although analyses were limited by a small number of CVD events in e-cigarette users.
Dual use of cigarettes and e-cigarettes was associated with a significantly increased risk of CVD compared with non-use. The cardiovascular risk of dual use did not differ from the risk among those exclusively smoking cigarettes. Other recent cross-sectional analyses have also reported no significant association between e-cigarette use and CVD out-comes.
Limitations of this study include use of self-reported, non-adjudicated outcomes that could result in misclassification, a short follow-up period given the progressive development of CVD, and a non-use reference group that includes former cigarette users.
Larger studies with more cardiovascular outcome events and longer follow-up are warranted. Our results suggest that combining smoking with e-cigarette use does not reduce CVD events and that quitting both products is required to ensure a mitigation of risk.
See also from the MedicalBrief archives
US study finds many physicians have misconceptions about e-cigarettes
FDA approvals of e-cigarettes must be based on evidence, not politics
E-cigarettes: Misconceptions may prevent people from quitting smoking
The health pros and cons of e-cigarettes – Evidence ambivalence