Vaping may stiffen the heart and blood vessels

Vaping study in mice suggests e-cigarette use might lead to heart disease

E-cigarettes have been promoted as a healthier alternative to smoking tobacco. But vaping still holds risks, especially for children and teens.

6okean/istockphoto

Smoking’s ill effects on human health are well known. But electronic cigarettes have only been around for about 15 years. So there hasn’t yet been time to demonstrate any long-term risks. Still, short-term data already point to vaping’s risks to the lungs and DNA. Now a mouse study shows that even brief exposure to e-cigarette vapors hurts blood vessels.

Effects seen in mice after eight months of vaping were striking. Even more concerning: Just five minutes of vaping damaged their blood vessels. These types of injury increase the risk of developing heart disease. The findings therefore add to a growing list of harm being linked to vaping.

I. Mark Olfert works at West Virginia University in Morgantown. As a physiologist, he studies how the body works. His research focuses on the lungs, heart and blood circulation. Doctors in his state have been considering recommending vaping as a way to help their patients quit smoking. This concerned Olfert. When it came to the heart, he notes, “There really wasn’t any information whether e-cigarettes were safe.”

So his team decided to test the effects of long-term vaping in mice. They placed the animals in a chamber filled with e-cigarette vapor for four hours daily. They continued this for eight months. The exposures these mice got was no higher than what an average vaper now experiences, Olfert reports. Mice live for two to three years. So their eight months of vaping was about the same as 20 years of vaping by a human. 

Arteries carry blood from the heart to the blood vessels that feed cells in even the most distant tissues of the body. The researchers measured the stiffness of a primary artery running from the heart into the lower chest. Mice exposed to the vapors had arteries that were 2.5 times stiffer than normal. Stiff blood vessels can lead to life threatening heart disease.

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An e-cigarette device attached to a tube pumps vapors into a lab chamber. Effects seen in mice suggest vaping poses a risk of heart disease.Mark Olfert and WVU Photography Services

However, in these tests, just five minutes of vaping also had a clear impact. When muscles in an artery’s walls are stimulated, they contract. This temporarily reduces the size of the tube’s interior. That also ups an individual’s blood pressure. So it’s important that blood vessels don’t stay contracted for too long. But after a mouse had vaped, its artery responded more slowly than normal to chemicals that instruct it to relax, or dilate. The artery’s slow response could weaken the heart over time, Olfert says.

Taken together, he concludes, these data suggest that even brief vaping is not safe for the heart. His team described its findings online November 2 in the Journal of Applied Physiology.

 Mice are different from people, Olfert points out. But often, not that much different. For instance, cigarette smoking has similar effects in mice and people. That’s one reason his team expects its rodent data may predict human heart impacts from vaping. And while it would be nice to have actual human data for comparison, it could take 20 or 30 more years before long-term vaping data would be available from people, he notes.

Importance for teens

Vaping research is especially important for young people, who might unknowingly put their health at risk. “With adolescents, we are really concerned,” stresses Olfert, “because right now the message they get is that these things are safe.” In fact, he notes, a wealth of emerging data suggest e-cigarettes aren’t.

Holly Middlekauff agrees. She is a heart doctor at the University of California in Los Angeles who did not take part in the new study. Many people today view vaping as harmless. And that, she says, is a mistake. Such a belief, she worries, may lead teens who would otherwise not have tried traditional tobacco cigarettes to experiment with vaping.

The next step is to find out which part of an e-cigarette’s vapor is responsible for the artery and blood-vessel impacts. “Is it the nicotine,” asks Olfert? “Is it the base chemicals that are in the [vaporized] liquid? Or is it the flavoring?” Right now, he notes, “we don’t know.”

Middlekauff suspects nicotine might be the heart-toxic component. Nicotine is a natural chemical in tobacco that makes cigarettes addictive. The toxicity of smoking is usually blamed mostly on the tars that form when tobacco is burned. As e-cigarettes “burn” nothing, some people had assumed vaping was harmless. But the safety of inhaled nicotine is not proven, Middlekauff points out. In fact, there are reasons to believe that nicotine may be particularly harmful to teens.

Her team recently tested the effects of e-cigarettes with and without nicotine in human volunteers. People who inhaled vapors containing nicotine showed fluctuating heart rates. That is what people would expect from nicotine. So the new data seem to affirm that nicotine “may underlie the adverse effects on the heart,” she says. Her team reported its findings in the September Journal of the American Heart Association.

Olfert’s group is continuing to study long-term effects of vaping on blood vessels. These researchers have even begun a study in people based on their results in mice.

For now, Middlekauff urges, teens should know that vaping is not harmless. “If you are a non-smoker,” she says, you definitely “should not start using electronic cigarettes.”     

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