A US study titled Association Between Electronic Cigarette Use and Myocardial Infarction, published on AJPM, surveyed 69,046 people in 2014 and 2016 to assess the risk between e-cigarette use, smoking, and the likelihood of experiencing a heart attack.

The researchers said that compared to those who had never used e-cigarettes, participants who used e-cigarettes daily had a higher chance of suffering a heart attack. However, when compared to those who smoked regular cigarettes, vapers had a lower chance.

“Daily e-cigarette use was independently associated with increased odds of having had a myocardial infarction (OR=1.79, 95% CI=1.20, 2.66, p=0.004) as was daily conventional cigarette smoking (OR=2.72, 95% CI=2.29, 3.24, p<0.001).”

On the other hand, former or occasional vapers seemed to not be at risk ‘of ever having a heart attack whilst former smokers did. “Former and some day e-cigarette use were not significantly associated with having had a myocardial infarction (p=0.608 and p=0.392) whereas former (OR=1.70, p<0.001) and some day cigarette smoking (OR=2.36, p<0.001) were.”

Earlier this year, a similar study claiming that vaping causes heart attacks, was presented at the annual meeting of the Society for Research on Nicotine and Tobacco (SRNT). The following week, Public Health expert Dr. Michael Siegel, had published an article exploring the compiled data and what it means.

A correlation does not equate to causation

Dr. Siegel had pointed out that this study indicates a correlation, not causation, and this correlation could be bidirectional. “Before accepting the conclusion that vaping causes heart attacks in unsuspecting smokers, remember the old adage: correlation does not equal causation. This study is a perfect demonstration of that phenomenon,” said the public health professor.

“Before accepting the conclusion that vaping causes heart attacks in unsuspecting smokers, remember the old adage: correlation does not equal causation.” Dr. Michael Siegel, Professor in the Department of Community Health Sciences, Boston University School of Public Health.

“Because this is a cross-sectional study, and because respondents were asked whether they had ever had a heart attack, one cannot determine whether the heart attacks followed e-cigarette use or preceded it. In other words, we do not know that vaping preceded the heart attack for any of the subjects. It is entirely possible that in most of these cases, the smokers suffered a heart attack and then started vaping in an attempt to quit smoking,” added Siegel.

It is likely that smokers switched to vaping after experiencing a heart attack

Siegel explained that it is not even “biologically plausible” that vaping would elevate the the risks of cardiovascular disease beyond that of smoking, because the cardiovascular effects of smoking get saturated at very low levels, and beyond that there is very little additional risk. On the other hand, he added, it is very plausible that smokers may try quitting smoking by switching to e-cigarettes, after having experienced a heart attack.

“Because this is a cross-sectional study, and because respondents were asked whether they had ever had a heart attack, one cannot determine whether the heart attacks followed e-cigarette use or preceded it.” Dr. Michael Siegel, Professor in the Department of Community Health Sciences, Boston University School of Public Health.

Hence, concluded Siegel, before making claims about causation, longitudinal studies are required to confirm such findings. “This single cross-sectional study is not enough because there is no way to tell the direction of the observed association between current use of e-cigarettes and having experienced a heart attack in the past,” concluded Siegel at the time.