First evidence that e-cig use increases heart attacks, independent of the effect of smoking cigarettes

Every time I have posted a comment on a new study showing that e-cigarettes adversely affect blood vessels and blood in ways that increase risk of a heart attack, a friend and colleague who remains part of the (shrinking) collection of e-cigarette enthusiasts emails me and with he comment that, “if they are so bad where’s the evidence that e-cigarettes increase the risk of a heart attack?”
 
The first evidence just appeared.
 
Using the National Health Interview Survey (NIHS), a large national survey done in the US, Nardos Temesgen and colleagues at George Washington University, found that the odds of a heart attack  increased by 42% among people who used e-cigarettes. 
 
This increase in risk was on top of the increases in risk due to any smoking that the e-cigarette users were doing.  This  is a particularly important finding because most e-cigarette users are dual users who keep on smoking at the same time that they use e-cigarettes.  What this means is that dual use of e-cigarettes with cigarettes is substantially more dangerous than smoking alone.
 
The assumption of most people – including me – has been that e-cigarette use would not add much risk to cigarettes.  That is not the case.  E-cigarette use increases the risk of a heart attack about as much as having diabetes.
 
The work also controlled for a wide range of confounding variables.  In addition, the risks associated with other factors (like smoking, diabetes, and high blood pressure) in this study were similar to those established in earlier work.  This fact strengthens the conclusions that e-cigarettes represent an independent cause of heart attacks.
 
The abstract of the study, “A cross sectional study reveals an association between electronic cigarette use and myocardial infarction,” is available here.
 
Here is the abstract:
 
Background: E-cigarettes (E-cigarettes) have grown in popularity as an alternative to traditional cigarettes especially among consumers who want to reduce the risk of morbidity and mortality associated with smoking. Nonetheless, a recent study showed both E-cigarettes and traditional cigarettes cause an increase in oxidative stress and endothelial dysfunction, however this effect is less pronounced with E-cigarettes. Currently, there is a limited study that shows the impact of E-cigarette in the cardiovascular system. Therefore, data from the 2014 National Health Interview Survey (NHIS) was used to evaluate the effect of E-cigarettes on the cardiovascular system, specifically the effect on myocardial infarction (MI).
Methods: Analysis of the 2014 National Health Interview Survey (NHIS) database was performed to examine the effect of E-cigarettes on MI. Initially, subjects were assigned to one of two groups: those with a history of MI and those without a history of MI. The t-test and chi-square test were subsequently applied to compare the different demographics and health characteristics between these two groups. A logistic regression model was then used to measure the association between E-cigarettes and history of MI. Data was adjusted for multiple risk factors for MI including age, gender, race, body mass index, income, the status of smoking cigarettes, and history of hypertension, diabetes, and hypercholesterolemia.
Results: A total of 35,156 subjects were included in the final logistic model. This model showed that increasing age (OR, 1.04; p <0.001), history of hypertension (OR, 2.72; p < 0.001), high cholesterol (OR, 2.19; p< 0.001), and diabetes (OR, 1.68; p< 0.001) are associated with increased odds of myocardial infarction. With respect to smoking, increased frequency of smoking was associated with increasingly higher odds of MI when compared to patients who had never smoked: every day smokers (OR, 2.75 p<0.001), some day smokers (OR, 2.39; p<0.001), and former smokers (OR 1.80; p<0.001.) In contrast, females (OR, 0.49; p<0.001), Hispanics (OR, 0.62; p<0.001), and people with higher incomes (OR, 0.93 [95% CI, 0.90-0.96]; p<0.001) have lower odds of heart attack. With respect to Electronic cigarette use and MI, analysis revealed an odds ratio of 1.42 with p = 0.017.
Conclusions: Our findings indicate that Electronic cigarette use, when adjusted for other risk factors, is associated with a 42 % increased odds of myocardial infarction. This increase in odds is consistent regardless of traditional cigarette smoking history. More studies are needed to further assess this risk.
 

Comments

Are you sure...

This is only a poster by a group of new young MDs with no apparent expertise in tobacco control, toxicology, statistics or any branch of relevant science - are you confident it is a rigorous study that demonstrates significant association between e-cigs and heart attacks? 

Yes

I have checked.  The authors are postdoctoral fellows and medical residents, some with formal statistical training.  (Those are the people who do a lot of the medical research that gets published.)
 
This poser was presented at the American College of Physicians meeting in San Diego, which is peer reviewed.  It won an award there.

Causality

"The work also controlled for a wide range of confounding variables."
 
Did it control for whether the subjects had their heart attack before or after they started vaping? The reason I ask is that I started vaping because I had a heart attack. 

I would stop vaping right now

If you stopped smoking cigarettes and switched entirely to e-cigs you likely have a lower cancer risk, but you are probably not having much effect on herat attack risk.
 
If you are continuing to smoke while you vape you are probably increasing your overalll risk.

This is a cross-sectional study, subject to reverse-causality

Heart attacks cause quit attempts. So why would we not expect to find increased e-cigarette use among smokers with a history of myocardial infarction?
Also if more dependent smokers are more likely to use e-cigarettes, then EC use is likely correlated heavier smoke exposure.

Unlikely

While this is a theoretical problem, if what you are suggesting is what was happening, the e-cig effect would not have been significant, since it would be captured in the cig smoking variables.  The fact that the other covariates (including the smoking effect) are all similiar to other estimates, including longitudinal studies, also argues against this idea.
 
In addition, the fact that, as I said in the original blog post, this is exactly what would be expected based on the biology, strengthens the confidence one can have in the epidemiological results,

Effects of E Cigs on health

Good evening Dr. Glantz,
I smoked about a pack a day from age 14-28. I started again over 15 years later smoking now and then. I picked up the habit full blown, smoking over a pack a day when my husband passed away five years ago. I hated myself for it, hated the smell, the cost, and what it was doing to my lungs. As an RN, I'm fully aware of all the negative effects of the nasty habit. I tried everything to quit again. Chantex was helpful, but I hated the S/E. (Nightmares, nausea, palpitations, etc) Gum, Wellbutrin, the patch, cold turkey, even hypnotism. Nothing worked. Than I half heartedly tried the e-cig aka the vape. It quelled the urge for about 2 hours and again for another 2, etc. I smoked a few cigarettes here and there the first week, but found that I liked the vape better. No nasty smell, very little cost, better flavor. It worked. I tried different devices that were more efficient and less costly. I have decreased my nicotine content from 12 mg to 3 mg. I will shortly be on 0 mg. I have been vaping for about 2 years now. I plan on dropping it completely in the next few months. I can leave home without it. No rushing back or stopping to buy more. No urge when out with friends for hours. I can breath exponentially better. I will never smoke another cigarette again as I can't stand the smell. I suppose that is because my sense of smell has vastly improved as well. The jury is still out on E cigs and the effect on our health, but it seems that the government and medical field are ready to crucify the e cig industry with little facts. There are many variables w vaping that are somewhat different than say a pack a day smoker. Vape fanatics inhale huge amounts of the product with high nicotine levels incessantly throughout the day. I'm not that type of vape smoker. I wonder if the habits of the vape user are taken into consideration with these studies. We can't say for sure what the effects of E-cigs will have on the body, and I am no scientist. As I exercise frequently and eat well, I have no hypertension, cholesterol or obesity issues, I don't fear an MI. I can say from my own experience, that the product is far safer than cigarettes as well as Chantex. It was the catalyst that broke my hold on cigarettes and lastly, tobacco. And for that Dr., I am eternally grateful. I'm sure there are many vape users out there with like stories. I think success stories such as these have to be taken into account in your research and work which I find commendable nonetheless.
Thank you for your time.
Doriana Donovan, RN

Probably less cancer, but not heart disease

As I noted in the original blog post, the data are still accumulating on the effects of e-cigarettes.
 
I agree that if you switch entirely from conventional cigarettes to e-cigarettes that is less dangerous.  You get a much lower dose of cancer-causing chemicals. 
 
But the evidence is rapidly accumulating that e-cigarettes substantially increased hearts and non-cancer lung disease risk.
 
My advice:  Now that you have stopped cigarettes, stop the e-cigarettes.
 
(Most e-cigarette users continue to smoke; for most people e-cigarettes make it harder to quit cigarettes.)