A new study presented Saturday at the annual meeting of the Society for Research on Nicotine and Tobacco (SRNT) concludes that vaping causes heart attacks, increasing the heart attack risk for dual users beyond that of smoking alone. The research has not yet been published but was presented as a poster at the conference.
The study was a cross-sectional analysis of nearly 70,000 respondents to the combined 2014 and 2016 National Health Interview Surveys (NHIS), a nationally representative survey of health risk factors and outcomes in U.S. adults. Respondents were asked to report their current vaping and smoking statuses and to report whether they had ever had a heart attack. The researchers found that there was a significant association (odds ratio = 1.8) between daily e-cigarette use and having experienced a heart attack. The analysis controlled for level of current cigarette use.
Based on this observation, the study concludes that daily e-cigarette use doubles the risk of heart attacks.
The Rest of the Story
Hold your horses.
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.
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. In fact, I believe that is the most likely explanation for the observed study findings.
It is not even biologically plausible that vaping could increase the risk of cardiovascular disease beyond that of smoking. Why? Because the cardiovascular effects of tobacco smoke saturate at a very low level, meaning that it takes only a little exposure to increase your risk. But beyond that, there is little additional risk.
On the other hand, it is quite plausible that smokers make quit attempts after experiencing a heart attack and that in recent years, these quit attempts have often involved the use of e-cigarettes.
It is true that many of the adverse effects of smoking were first observed in cross-sectional studies. However, these were followed up with longitudinal studies that confirmed the findings. Before we reach a conclusion on whether vaping poses a heart attack risk, we need longitudinal studies. 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.
Although I question the validity of the study's conclusions, it is still important to emphasize that smokers who use e-cigarettes should aim to quit smoking completely. The full health benefits of vaping will not accrue to smokers unless they quit smoking completely. Dual use - if the cigarette consumption drops substantially - will reduce respiratory disease risks, but it will not reduce cardiovascular disease risk because of the saturation phenomenon noted above.
