A study published in JAMA Cardiology concludes that chronic e-cigarette users may be putting themselves at risk of cardiovascular disease. The study sample, which was small and not without limitations, looked at 23 habitual e-cigarette users and 19 non-tobacco, non-e-cigarette users. All the participants were in good health with a median age of 27.6 years. About two-thirds were men, and two-thirds were non-white.
After performing electrocardiograms on the study participants over the course of a year, the researchers found that heart rate variability shifted toward “increased sympathetic predominance” in the e-cigarette users. This measure of heart activity is a known indicator of increased cardiovascular risk.
The researchers also found that low-density lipoprotein oxidizability, a measure of oxidative stress and also an indicator of cardiovascular disease, was greatly elevated in the e-cigarette users.
“Rather than wait decades for epidemiological data in habitual e-cigarette users to become available, we reasoned that investigations into several of the known mechanisms by which tobacco cigarettes increase cardiovascular risk would provide insights in the health risks of e-cigarettes,” wrote the researchers, led by Roya S. Moheimani and colleagues at University of California, Los Angeles.
“Abnormal (heart rate variability) is present in tobacco cigarette smokers and has been shown in populations with and without known cardiac disease to identify those at risk for myocardial infarction (heart attack) and sudden cardiac death. Additionally, increased oxidative stress and inflammation are major mechanisms by which tobacco cigarettes initiate and propagate atherosclerosis (hardening of the arteries). Each puff of cigarette smoke contains greater than 10 free medicals.”
Are E-Cigarettes Still Safer than the Regular Kind?
There is considerable debate within the medical community over e-cigarettes. Some argue e-cigarettes present a harm reduction model for quitting smoking, which can be a tough road. Harm reduction means that while a person may not be stopping an unhealthy addiction entirely, at least they are greatly reducing their risks associated with the habit.
Other doctors and scientists argue that there is so little known about electronic cigarettes – for example, the contents of “the juice” varies widely – that we don’t even known if the harm reduction argument really applies.
“Other reports showed significant variability between e-cigarette liquids, with only one in 11 liquids tested inducing significant oxidative stress in cultured human endothelial cells,” the authors wrote.
“Nonetheless, it remains likely that the heated aerosolized nicotine, the humectants (propylene glycol/glycerol) and/or flavorings, all known or potential airway irritants, could lead to the presence of reactive oxygen species in the human airway, in turn leading to systemic oxidative stress. Our e-cigarette users used a variety of flavored liquids and brands, all containing nicotine, suggestive of an oxidative effect that is ubiquitous from habitual e-cigarette use.”
In addition to the small sample size, the authors admit the study has other limitations. For example, since it relied on self-reporting, there is no way to tell whether some of the e-cigarette users were also smoking tobacco cigarettes or other combustible materials such as marijuana.
E-Cigarettes May Reduce Cancer Risk
In an accompanying editorial, Aruni Bhatnagar of the Division of Cardiology Medicine at the University of Louisville in Kentucky (the heart of tobacco country), reports, “Because oral nicotine is relatively well tolerated even by individuals with cardiovascular disease, it is unclear whether changes in (heart rhythm) alone could be regarded as an indication of substantial cardiovascular injury. However, oral nicotine also may not be innocuous because individuals who quit smokeless tobacco have been reported to decrease their cardiovascular risk to an extent similar to those who quit smoking.”
An increase in heart rate by itself could create hardening of the arteries over time, Bhatnagar wrote, “Hence, persistent changes in (heart rhythm) observed in e-cigarette users reinforce the idea that nicotine, whether delivered by a combustible cigarette or e-cigarettes, is not a harmless drug but could have significant adverse cardiovascular effects.”
The authors of the study concede that “Because e-cigarettes lack tar and other carcinogens, their carcinogenic (cancer-causing) effects may be lower than combustible cigarettes; however, it is unclear whether cardiovascular harm is similarly attenuated.”