June 6, 2019

Stanton A. Glantz, PhD

More evidence that e-cigs cause heart attacks, this time from PATH

Dharma Bhatta and I just published “Electronic Cigarette Use and Myocardial Infarction Among Adults in the US Population Assessment of Tobacco and Health” in Journal of the American Heart Association.  Like earlier analyses, we found an independent effect of e-cigarette use on risk of having had a heart attack (myocardial infarction) when controlling for smoking and other clinical and demographic factors.

The odds of having had a heart attack among daily e-cigarette users were more than doubled compared to people who neither used e-cigs not smoked cigarettes.  We also found a statistically significant dose-response, with people who used e-cigs daily having higher risks than nondaily, former, or never users.

While the point estimates of the risks of former, nondaily, and daily e-cigarette use are lower than the comparable numbers for smoking cigarettes, the “margins of error” (95% confidence intervals) for e-cigarettes and cigarettes overlap, suggesting that for heart attacks, the risks of e-cigs and cigarettes are comparable.  

This finding is what one would expect based on what is known about the biological effects of e‐cigarette use.

A standard criticism of cross-sectional studies like this is so-called “reverse causality” which would happen if smokers who had heart attacks preferentially used e-cigarettes to try and quit smoking.  That situation would also create the association we detected.  We specifically tested whether smokers who had heart attacks were more likely to use e-cigarettes.

We used the longitudinal data in PATH to test directly for reverse causality by testing whether having had a myocardial infarction at Wave 1 predicted e‐cigarette use at Wave 2 among people who were cigarette smokers at Wave 1. The results did not approach statistical significance (P>0.62 for all outcomes), strongly suggesting that reverse causality is not an issue. (The presence of a statistically significant dose‐response is also consistent with a causal effect.) 

Former, some‐day, and every‐day combustible cigarette smoking is also independently associated with myocardial infarction among adults in the United States. Because e-cigs and cigarettes are independent risks for heart attack, dual use of the e‐cigarette and combustible cigarettes results in higher risk of myocardial infarction than using either product alone.

In addition, switching from cigarettes to e‐cigarettes was not associated with any benefits in terms of reduced myocardial infarction risk.

E‐cigarettes should not be promoted or prescribed as a less risky alternative to combustible cigarettes and should not be recommended for smoking cessation among people with or at risk of myocardial infarction.

Here is the abstract:

Background-—E-cigarettes are popular for smoking cessation and as an alternative to combustible cigarettes. We assess the association between e-cigarette use and having had a myocardial infarction (MI) and whether reverse causality can explain the observed cross-sectional association between e-cigarette use and MI.

Methods and Results-—Cross-sectional analysis of the Population Assessment of Tobacco and Health Wave 1 for association between e-cigarette use and having had and MI. Longitudinal analysis of Population Assessment of Tobacco and Health Waves 1and 2 for reverse causality analysis. Logistic regression was performed to determine the associations between e-cigarette initiation and MI, adjusting for cigarette smoking, demographic and clinical variables. Every-day (adjusted odds ratio, 2.25, 95% CI: 1.23–4.11) and some-day (1.99, 95% CI: 1.11–3.58) e-cigarette use were independently associated with increased odds of having had an MI with a significant dose-response (P<0.0005). Odds ratio for daily dual use of both products was 6.64 compared with a never cigarette smoker who never used e-cigarettes. Having had a myocardial infarction at Wave 1 did not predict e-cigarette use at Wave2(P>0.62), suggesting that reverse causality cannot explain the cross-sectional association between e-cigarette use and MI observed at Wave 1.

Conclusions-—Some-day and every-day e-cigarette use are associated with increased risk of having had a myocardial infarction, adjusted for combustible cigarette smoking. Effect of e-cigarettes are similar as conventional cigarette and dual use of e-cigarettes and conventional cigarettes at the same time is risker than using either product alone. (J Am Heart Assoc. 2019;8:e012317.DOI: 10.1161/JAHA.119.012317.)

The full citation is:  Bhatta D, Glantz S.  Electronic Cigarette Use and Myocardial Infarction Among Adults in the US Population Assessment of Tobacco and Health.  J Am. Heart Assn. https://www.ahajournals.org/doi/10.1161/JAHA.119.012317   https://www.ahajournals.org/doi/pdf/10.1161/JAHA.119.012317

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