A new study published online ahead of print in the American Journal of Medicine reports that there is no association between vaping and cardiovascular disease among never smokers.
Like previous studies of its kind, this was a cross-sectional study that examined the association between current vaping/smoking status and ever having been told that one has cardiovascular disease (including heart attack, coronary artery disease, or stroke). Previous studies used data from the National Health Interview Survey (NHIS) or the Population Assessment of Tobacco and Health (PATH) study; this paper used data from the Behavioral Risk Factor Surveillance Survey (BRFSS).
The authors reported no association between current vaping and self-reported cardiovascular disease among never smokers. However, they found that among current dual users there was an increased odds of having ever been told that one has cardiovascular disease.
In response to the study, one prominent tobacco control researcher concluded that dual use is causally associated with cardiovascular disease, while dismissing the negative finding that e-cigarette use was not associated with vaping among never smokers. He wrote: "The fact that the authors did not find an effect of e-cigarettes alone
may be because they stratified the sample on e-cig and cigarette use,
which reduces the sample size for each comparison, and so the power to
detect an effect."
The Rest of the Story
This reminds me of what the tobacco industry used to do. If they saw a finding that they liked, they would emphasize that finding, but if they saw a finding that they didn't like, they would just dismiss it. This is sometimes called "cherrypicking." I've never picked cherries, but I assume that when doing so, one only picks the cherries that you like and disregards the ones that you don't.
As objective scientists, we can't cherrypick. It allows one to have a pre-conceived conclusion and then to simply publicize findings that support the conclusion while dismissing those that do not. It appears that this is what is going on here.
Cherrypicking is becoming more and more common among tobacco control researchers and advocacy groups. Recently I spoke at a conference on vaping, and one of the other speakers on the panel told the audience that there was no evidence vaping can help people quit smoking. The basis of that conclusion was that "there is no clinical trial that shows vaping to be effective ... we need a clinical trial." When I then pointed out that a randomized, clinical trial published last month in the prestigious New England Journal of Medicine found that vaping was twice as effective as nicotine replacement therapy for smoking cessation, they simply dismissed it, saying: "Well I still don't think it's effective." (The same person also did not think there is enough evidence to conclude that vaping is any safer than smoking.)
The reality is that many tobacco control researchers and advocates will not be convinced by any amount of data. You could have two clinical trials, both finding that vaping is effective for some smokers, and they would still dismiss the findings. (In fact, we do have two clinical trials -- it's amazing to see how many tobacco control advocates continue to insist that there have not been any clinical trials on the use of vaping for smoking cessation.)
Here, a positive finding is accepted and touted, while a negative finding is just dismissed. The reasoning given -- that the study didn't have the power to detect an effect -- doesn't hold water because the sample size of never smoking vapers in the study (15,863) exceeded the number of dual users (12,908).
But even the conclusion that dual use is causally associated with cardiovascular disease is unsupported by the evidence presented in the paper. This is a cross-sectional study, so it is entirely possible that the onset of cardiovascular disease preceded the vaping. In fact, this is almost certainly the case for most of the study subjects because e-cigarettes have been popular for only about eight years, and it takes decades for cardiovascular disease to develop.
It may actually be that the cardiovascular disease "caused" the vaping because having a heart attack or stroke is a strong stimulus for a smoker to try to quit, and many smokers try to quit by using e-cigarettes.
Moreover, dual users are almost certainly a different population from exclusive vapers and one systematic difference between the groups is likely that dual users have a heavier or more intense smoking history, making it more difficult for them to get off of e-cigarettes. If this were the case, it would explain the observed finding that dual use was associated with a higher risk of reporting cardiovascular disease.
The bottom line is that we can't draw causal conclusions from a cross-sectional study like this one, especially one in which it is impossible to determine which came first: the heart attack or the vaping. So to tout the association between dual use and heart disease as a causal finding is bad enough. But cherrypicking findings that support a pre-determined conclusion, while dismissing those which do not support that conclusion, is sinking to the level of the tobacco industry which we once criticized for doing the very same thing.