Long Term E-Cigarette Use Harms Vascular Function

E-cigs would seem like they should be safer for the heart, as that is how they are marketed, but preliminary research suggests that this is not the case according to some research. One study in 2018 cites adverse changes involving endothelial function, vascular stiffness, vasoconstriction, heart rate, blood pressure, inflammation, oxidative stress, and platelet function which was seen in over a dozen studies conducted in high income countries. 

“A lot of the other studies that have come out so far have looked at what happens to blood vessels just after someone uses an electronic cigarette,” said Jessica L. Fetterman, PhD (Boston University School of Medicine, MA), the new paper’s lead author. “They haven’t really looked at: what are the cardiovascular impacts associated with e-cigarette use over a longer period?”

The Cardiovascular Injury Due To Tobacco Use Study published in the Journal of the American Heart Association focused on chronic smokers looking at a heterogeneous group in terms of demographics with differences that could affect vascular function, that established smokers habits dating at least three months prior to enrollment, and all e-cigarettes users were former smokers. 

“It’s an interesting study. It’s intriguing. But there’s still a lot more that needs to be done before we accept [that e-cigarettes are no better]. I think the data’s just not there yet” said Holly R. Middlekauff, MD (UCLA Health, Los Angeles, CA).

467 participants without cardiovascular disease or risk factors for the disease were enrolled; 61% used regular cigarettes, 8% used e-cigs, 11% were dual users, 20% were non-smokers and the mean number of smokes and years spent smoking were similar for the cigarette smokers and dual users. 

Baseline brachial diameter and flow velocity, flow mediated dilation, shear stress, reactive hyperemia, and heart rate was similar across all groups while measures for arterial stiffness including carotid femoral pulse wave velocity, carotid radial PWV, augmentation index, and central blood pressure differed. 

After taking into account age, race, gender and study site multivariable models showed that the augmentation index was significantly higher among smokers compared with nonsmokers, but it was similar to e-cig users; and endothelial cell analysis found that “stimulated nitric oxide production was diminished in both combustible and e-cigarette users, suggesting the presence of endothelial cell dysfunction.”

These findings are at odds with a trial involving 114 participants that was published in the Journal of the American Heart Association in 2019 that found significant improvement in flow mediated dilation within one month of switching from smoking to e-cigs. 

Middlekauff says that flow mediated dilation is “highly validated to be predictive. It’s one of the earliest signs of atherosclerosis or hardening of the arteries,” while augmentation index as a measure of vascular stiffness “is less studied and less frequently used, . . . but it is valid. And it is interesting that it is different but only after they adjusted for all these differences in the populations. It’s a statistical approach that takes away some of the transparency and you just wish that the groups were better matched upfront . . . rather than have to do that mathematically.”

When asked how these studies fit together Fetterman replied, “We looked at slightly different measurements. And I think it is challenging to know both from their study and our study how many of the e-cigarette users truly switched completely to e-cigarettes because we don’t have a good biomarker to look at.”

Urine testing that measures cotinine picks up all nicotine exposure no matter the source, “That’s been a real challenge. So how do you really validate that someone has only been using electronic cigarettes and been cheating with a cigarette here and there? We just don’t have that yet. I think there are some possible new ones coming. There’s been a lot of different studies trying to identify new biomarkers, but we don’t currently have a validated one yet.”

Literature suggests that e-cigs on the whole are not any safer than cigarettes for vascular health, and the evidence is accumulating showing that e-cigs are not good for you, says Fetterman. What it “suggests is that there’s no vascular improvement with switching to electronic cigarettes if you’re a smoker, and there are some studies suggesting there’s even harm in people that have never used tobacco [then] try using an e-cigarette, showing vascular impairments.”

Large long term studies are needed, says Fetterman. “Heart disease takes decades to develop so it’s going to be a while before we really know [e-cigarettes’ safety].”

Middlekauff says that for now e-cigs can’t be fully ruled out as a safer alternative as they have less carcinogens, and complicating the matter is the fact that the long term effects on the lungs isn’t known, “Again, we just don’t know what the chronic effects are. I don’t want to say that they’re safe or harmless” at this point, she concluded.

As to handling the uncertainty over e-cigs for cessation Fetterman says, “If that patient has tried all of the traditional nicotine replacement therapies and tried behavioral therapy and not been successful in quitting, I think it’s worth a shot,” she acknowledged. “But it has to be done with the guidance of a physician, and if possible a cessation team, to help that patient step down on the nicotine and really create a plan to get them off of all tobacco products. Maybe e-cigarettes could play a role in that process, but I think it’s really important for patients to work with a physician to do that.”