In a press release issued last April by the American College of Cardiology, researchers of a new study claimed that people who use e-cigarettes are 19% more likely to develop heart disease than people who do not.
According to the release: "People who use e-cigarettes are significantly more likely to develop heart failure compared with those who have never used them, according to one of the largest prospective studies to date investigating possible links between vaping and heart failure. The findings are being presented at the American College of Cardiology’s Annual Scientific Session. ... The results showed that people who used e-cigarettes at any point were 19% more likely to develop heart failure compared with people who had never used e-cigarettes."
The study was not released publicly. Instead, the researchers made available merely an abstract of the study. In fact, it appears that the study presented was merely a poster, not even an oral presentation.
The press release led to widespread headlines warning that using even a single e-cigarette could increase someone's risk of heart failure. For example, the headline of Medical News Today read: "Vaping, Even Once, May Raise the Risk of Heart Failure, Study Finds." That's pretty scary. If it is true that a single vape can increase your risk of heart failure by 19%, then e-cigarettes are one of the most dangerous substances out there. Is this scary propaganda warranted?
The Rest of the Story
Here's the problem. It is now 9 months after the press release and still there is no publicly available paper that we can examine to see whether these headlines are justified. This is a problem that I call "science by press release." It means releasing study results to the media before publishing your paper and without also providing your entire methodology and results. I find it troubling when investigators do this because there is no way for anyone to analyze the validity of the study conclusions when all you have are the conclusions and not the study!
The fact that the study will eventually published (albeit we are at nine months and there is no publication yet as far as I can tell) is no justification because the media has already spread these headlines and it's too late to take them back. Even if the study comes out and says: "Whoops - sorry we were wrong in our conference presentation," it's too late because the media are unlikely to publish a story headlined: "Abstract from 9 months ago was incorrect."
There are three exceptions to the impropriety of releasing study results before a paper is published. One is if you release the full study and not just the abstract or conclusions. Second is if you present the paper to an audience without media and do not issue a press release. Third is if the paper is of such immediate importance that it cannot wait (e.g., a study finding that a COVID-19 vaccine is effective may deserve sharing prior to publication).
None of these exceptions applies here. The full study was not released. The abstract was shared with the media at the time of presentation. And there is certainly no emergency that warrants the early release of these findings.
Now as to the findings themselves. This was a longitudinal study of a cohort of participants from the NIH All of Use Research Program. As described by the investigators: "Data on electronic nicotine product use was obtained from participants using the Population Assessment of Tobacco and Health-styled questions. We determined the association between electronic nicotine products use and incident HF using Cox proportional hazards models adjusted for demographic and socioeconomic factors, diabetes mellitus, hypertension, hyperlipidemia, BMI and concomitant substance use (cigarette, cigar, hookah, smokeless cigarette and alcohol use)."
The major finding was that "Compared to never users, ever users of electronic nicotine products had an increased risk of incident HF [heart failure] (aHR = 1.19, 95% CI 1.06 -1.35) in our fully adjusted model." This indeed means that compared to never e-cigarette users anyone who had ever used an e-cigarette experienced a 19% increased risk of developing heart failure. The problem, however, is that most people who use e-cigarettes do so because they are trying to quit smoking. Thus, the overwhelming majority of e-cigarette users are either current or former smokers. So how do we know that it was the e-cigarettes, rather than the tobacco cigarettes, that caused their heart failure?
The answer is that we don't, unless you stratify the results by use of tobacco products. In other words, you derive the risk estimates for heart failure among e-cigarette users who have never used tobacco products and then separately for e-cigarette users who have used tobacco products. Well, if you read the abstract carefully, the authors apparently did this. They report the following: "In sensitivity analysis, we excluded participants with a history of cigarette, cigar, hookah and smokeless cigarettes (aHR = 1.04, 95% CI 0.57 - 1.89)." In other words, when the investigators restricted the analysis only to e-cigarette users and non-users who had no history of tobacco use, they found no significant relationship between e-cigarette use and heart failure.
A 2022 paper published in the journal Circulation provides evidence that when you stratify by smoking status, you no longer find a link between e-cigarette use and cardiovascular disease. In a longitudinal analysis of the PATH study, my former colleagues at Boston University found that:
(1) Exclusive e-cigarette use was not associated with cardiovascular disease.
(2) Exclusive cigarette use was associated with a 53% increase in cardiovascular disease.
(3) Dual use did not increase the cardiovascular disease risk above that of smoking alone.
(4) Compared to smoking, use of e-cigarettes was associated with a 34% reduction in cardiovascular disease.
(5) Dual users had the same cardiovascular disease risk as exclusive smokers.
Nearly the same results were found when the outcome was heart attack, heart failure, or stroke (as opposed to any cardiovascular disease).
These findings suggest that neither e-cigarette use nor dual use of e-cigarettes with tobacco cigarettes was associated with an increase in cardiovascular disease [dual use was of course related to disease but not any more than smoking alone]. The study also suggested that switching from cigarettes to e-cigarettes substantially reduces one's risk of cardiovascular disease. This is not a surprise since the name for switching from cigarettes to e-cigarettes is quitting smoking, and quitting smoking is well known to produce rapid declines in cardiovascular disease risk.
The rest of the story is that practicing science by press release is troubling because it risks widely disseminating false information to the public before there is any opportunity to scrutinize the research, and by the time the paper is actually published it is far too late to correct misconceptions that have already been spread through the media. It appears that exactly this may have occurred regarding the cardiovascular disease risks associated with e-cigarette use.
