New Study Demonstrates Why Anti-Vape Academics are Wrong in Concluding that E-Cigarette Use Causes Heart Attacks and COPD

Numerous researchers and health groups have claimed that e-cigarette use increases the risk of heart attacks and COPD (example 1; example 2; example 3). For example, a clinician from UnityPoint Health warned that: "Vaping is bad for your heart. The truth is people who vape are 56% more likely to have a heart attack than non-smokers and 30% more likely to suffer a stroke." The American Lung Association warned that: "E-cigarettes also contain acrolein, a herbicide primarily used to kill weeds. It can cause acute lung injury and COPD and may cause asthma and lung cancer."

These claims are based on studies showing that e-cigarette users are more likely to experience cardiovascular and respiratory disease than people who don't use e-cigarettes. The problem with these studies is that people who use e-cigarettes are more likely to also have a history of significant cigarette smoking, which is the likely cause of the diseases they experience. While studies have attempted to control for smoking, the smoking histories are often crude and cannot fully adjust for the actual exposure to smoking. 

A new study published last week in the journal Respiratory Research sheds important light on this methodological issue. The study used data from the 2020 National Health Interview Survey to conduct a cross-sectional analysis of the relationship between e-cigarette use and smoking and COPD. As in previous studies, this one too found that among former smokers, the use of e-cigarettes appeared to increase the risk of COPD. In this study, former smokers who used e-cigarettes were 2.8 times more likely to have COPD than never users of both cigarettes and e-cigarettes. However, after controlling for the number of years since the person stopped smoking, this relationship disappeared. 

Similarly, former smokers who had used e-cigarettes in the past were 1.7 times more likely than never users of nicotine to report having COPD. This relationship disappeared, however, after controlling for either the number of years since they stopped smoking or the total number of years that they smoked.   

The authors conclude as follows:

"Our findings raise an important question about many previous studies that have reported e-cigarette associations. These results from previous studies are summarized in a recent meta-analysis; the pooled adjusted odds ratio for COPD comparing e-cigarette use to no use was 1.46 (1.31–1.61) [36]. Our findings raise the question of how much this pooled estimate would be attenuated if the individual studies had included key variables describing smoking history in their multivariable models. Importantly, pooled estimates can be biased if the estimates from the individual studies included are biased. For example, a prospective study of PATH Study data waves 1–5 by Cook et al. 2023 [37] found that e-cigarette use was not associated with increased incidence of COPD after controlling for cigarette pack years and cigarette use status. This difference highlights the importance of adequately controlling for cigarette associated variables, which we do in our study’s models." 

The Rest of the Story

These findings suggest that previous conclusions that e-cigarette use causes heart attacks and COPD (as well as lung cancer) are seriously flawed because they did not properly control for cigarette smoking history. The only foolproof way to control for smoking history is to examine the relationship between e-cigarette use and the outcome among never smokers. That way, there is no means by which smoking could confound the relationship. Every time that has been done, there has been no significant increase in disease risk among e-cigarette users (with the exception of several studies with exceedingly small sample sizes - only 1 or 2 cases of disease occurred).

Unfortunately, the cat is already out of the bag. Headlines throughout the country have informed the public that e-cigarettes cause heart disease, COPD, and lung cancer. I doubt this new study will get much publicity and even if it did, it's difficult to change people's minds once they hold a certain belief.

Ultimately, these premature conclusions and headlines harm the public's health because they deter many smokers from quitting using e-cigarettes and they may also lead e-cigarette users to go back to smoking.