E-Cigarette Smoking May Be Bad for Your Heart
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Smoking e-cigarettes may be bad for your heart, a small new study suggests.

The study found that certain markers for heart disease risk were higher in e-cigarette users than in nonusers. For example, e-cigarette users had higher levels of adrenaline in their hearts, compared with nonusers. They also had elevated levels of inflammation and oxidative stress (a process that can damage cells) in their bodies.

"This suggests that e-cigarettes have a more complicated effect than just the direct pharmacological effect of nicotine," said study co-author Dr. Holly Middlekauff, a cardiologist at the University of California, Los Angeles' David Geffen School of Medicine. That's because nicotine and other e-cigarette compounds "may set in motion a constellation of physiologic effects that persist, even when nicotine is out of the system," Middlekauff told Live Science. [4 Myths About E-Cigarettes]

E-cigarettes are an increasingly popular alternative to tobacco cigarettes. They produce no combustion and contain no tobacco, but deliver a heated mixture of nicotine and flavors to the mouth and lungs of the user. The medical community's reaction to e-cigarettes has been mixed, with significant controversy over whether e-cigarettes represent a "safer" alternative to tobacco cigarettes, the study said.

Because e-cigarettes do not burn tobacco, they do not produce the same toxic compounds as regular cigarettes do. Moreover, they produce very little tar or carbon monoxide, so many proponents of e-cigarettes claim that e-cigs are healthier than regular, "combustible" cigarettes, Aruni Bhatnagar, a professor of medicine at the University of Louisville, who was not involved in the study, wrote in an editorial commenting on the study.

However, the cardiovascular risks of e-cigarettes are largely unknown. That's significant, because e-cigarettes do contain some heart-related toxins present in tobacco smoke, including formaldehyde and acetone, Bhatnagar wrote. Nicotine can also affect heart function and health, he noted.

In the new study, a total of 16 e-cigarette users (defined as those who had been using e-cigarettes for at least one year) and 18 nonusers were studied. The participants were ages 21 to 45 and included both men and women. None of the participants smoked tobacco cigarettes at the time.

On the day of the study, the researchers took the participants to a quiet, temperature-controlled room, and measured the participants' heartbeats for 5 minutes while they rested and for another 5 minutes while they practiced controlled breathing. A separate blood test looked at markers of oxidative stress and inflammation, which told researchers how well the body was responding to harmful toxins.

The results indicated that the e-cigarette users showed increased levels of so-called sympathetic arousal, meaning increased adrenaline levels, in their hearts, compared with nonusers. The e-cigarette users also had higher levels of oxidative stress than nonusers did. Both increased adrenaline levels in the heart and oxidative stress are ways in which tobacco cigarettes can contribute to increased cardiovascular risk, the researchers said.

However, the researchers cautioned that the study had some limitations. First, it relied on self-reporting for behaviors such as e-cigarette use and tobacco cigarette use, which can be an unreliable method. (However, the researchers noted that they did test users' blood to confirm whether they had recently smoked tobacco cigarettes.) In addition, the researchers were unable to quantify just how many e-cigarettes the e-cig users had smoked, given the difficulty of measuring the liquid used by each per day.

Furthermore, more former smokers of tobacco cigarettes were in the e-cigarette-user group than in the nonuser group, though the researchers noted that they did not believe this explained the difference in their findings. Finally, the researchers cautioned that they cannot confirm a cause-effect relationship between e-cigarette use and cardiovascular risk based on this single, small study.

The researchers are also still unsure of how the effects of e-cigarettes on the heart compare to the effects of tobacco cigarettes on the heart, and future research is needed to determine this, Middlekauff said.

The takeaway? "If you don't already smoke tobacco cigarettes, don't start using e-cigarettes — they are not harmless," Middlekauff said.

The study and editorial are published today (Feb. 1) in the journal JAMA Cardiology.

Originally published on Live Science.