High adrenaline levels, oxidative stress seen in comparison with nonsmokers
Electronic cigarettes may increase the risk of heart disease, researchers at UCLA report.
The team found that two risk factors for heart disease were elevated in 16 e-cigarette users compared with 18 nonsmokers.
“The pattern was spot-on” for what has been seen in heart attack patients and those with heart disease and diabetes, says cardiologist Holly Middlekauff, a coauthor of the study published online February 1 in JAMA Cardiology.
But because the study only looked at a small number of people, the results are not definitive — just two or three patients can skew results, John Ambrose, a cardiologist with the University of California, San Francisco cautions. Plus, he says, some of the e-cigarette users in the study used to smoke tobacco, which may have influenced the data.
Even so, Ambrose called the study interesting, noting that “the medical community just doesn’t have enough information” to figure out if e-cigarettes are dangerous.
E-cigarette users in the study had heartbeat patterns that indicated high levels of adrenaline — also known as epinephrine — in the heart, a sign of heart disease risk. Researchers also found signs of increased oxidative stress, an imbalance of certain protective molecules that can cause the hardening and narrowing of arteries.
Previous research has connected oxidative stress to e-cigarettes. The new study targeted where it might occur and how it could contribute to heart disease, says Aruni Bhatnagar of the American Heart Association Tobacco Regulation and Addiction Center based at the University of Louisville in Kentucky.
This study “adds to the case that there may be some residual harm associated with e-cigarettes,” says Bhatnagar, whose editorial on e-cigarettes and heart risk appears in the same issue of JAMA Cardiology.
Nicotine, the addictive substance found in both tobacco and electronic cigarettes, is known to elevate adrenaline levels. To ensure that they were measuring the long-term effects of vaping and not just the presence of nicotine, the researchers had their subjects refrain from using e-cigarettes the day of the tests.
The findings are important, Middlekauff says, because they show that e-cigarette users' hearts are in “flight or fight” mode all the time, not just when they are smoking.
The next step is to nail down exactly what in e-cigarettes is responsible for these effects on the heart, Middlekauff says. The researchers also want to compare e-cigarettes’ effects on the heart with tobacco cigarettes’.
“Electronic cigarettes aren’t harmless,” Middlekauff says. “They have real, measurable physiological effects and these physiological effects, at least the couple that we found, have been associated with heart disease.”
R. Moheimani et al. Increased cardiac sympathetic activity and oxidative stress in habitual electronic cigarette users. JAMA Cardiology. Published online February 1, 2017. doi: 10.1001/jamacardio.2016.5303
A. Bhatnagar. Are electronic cigarette users at increased risk for cardiovascular disease? JAMA Cardiology. Published online February 1, 2017. doi: 10.1001/jamacardio.20165550
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