April 30, 2016

Stanton A. Glantz, PhD

Important new study shows immediate effects of e-cigs on the cardiovascular system as big as smoking a cigarette

While e-cigarettes deliver lower levels of carcinogens than conventional cigarettes, they deliver the same, or a more dangerous, amount of ultrafine particles than conventional cigarettes.   Ultrafine particles trigger inflammatory processes that lead to heart and lung disease and can trigger heart attacks.  E-cigarette optimists have discounted possible effects of the ultrafine particles  in e-cigarettes, arguing that the literature linking particles to heart disease and heart attacks is based on research on air pollution and active and passive smoking, all of which involve combustion.
A new, very well done study by Roberto Carnevale and colleagues, “Acute impact of tobacco versus electronic cigarette smoking on oxidative stress and vascular function,” published in Chest on April 11, 2016, puts this argument to rest.  They show that smoking one e-cigarette impacts the functioning of arteries as much as smoking a conventional tobacco cigarette in nonsmokers and smokers alike.
Your arteries are constants adjusting how big they are in order to provide the blood that your heart and other organs need.  They do so through so-called flow mediated dilation (FMD): when an organ’s (like the heart) need for blood increases, the rate of flow inside the artery increases, which increases friction against the lining of the artery (known as the vascular endothelium).  This friction stimulates the endothelium to produce a chemical called nitric oxide (NO), which makes the muscle in the artery relax and the artery gets bigger to accommodate the increased need for blood flow.
Impaired FMD (and related processes) is involved triggering and responding to a heart attack and is also a predictor of atherosclerosis in the long term.
Carnevale and colleagues did an experiment in which they measured FMD and related biological intermediates before and after nonsmokers and smokers smoked one cigarette and one e-cigarette (on separate days).  They found, as expected, that smokers had lower FMD than the nonsmokers.   Most important, smoking one conventional cigarette and smoking one e-cigarette both reduced FMD  to the same extent (p = 0.311).
They also measured available NO and found that e-cigarettes, like cigarettes, depressed NO production.  As with FMD, smokers had lower levels of NO than nonsmokers, but e-cigarettes as well as conventional cigarette use depressed it as well.

Finally, they measured several measures of inflammation and found significant adverse changes following cigarette and e-cigarette use, although the adverse  effects of e-cigarette use were a little smaller than for cigarettes (chart below).  Changes in the antioxidant Vitamin E were the same for cigarettes and e-cigarettes (p=0.413).
These effects are, frankly, bigger than I expected.  Given than heart and vascular disease and noncancer lung disease cause over half the smoking-induced deaths, e-cigarettes could be half as dangerous as conventional cigarettes even if they cause no cancer.
In any event, the risk is a lot higher than the made up estimate that 5% as dangerous as cigarettes being popularized in by Public Health England and the Royal College of Physicians in England and by e-cigarette enthusiasts in the USA.
Also:  Several of these factors play a role in bronchospasm, which helps explain why people using e-cigarettes have decreased lung function and kids who use e-cigarettes have more respiratory problems.
Here is the abstract for the paper:

Background: The vascular safety of electronic cigarettes still needs to be clarified. We compared the impact of electronic cigarettes versus traditional cigarettes on oxidative stress and endothelial function in healthy smokers and non-smoker adults.
Methods: We performed a cross-over single-blind study in 40 healthy subjects (20 smokers, 20 non-smokers, matched for age and sex). Firstly, all subjects smoked T-cigarettes. One week later the same subjects smoked an E-cigarette with the same nominal nicotine content. Blood samples were drawn just before and after smoking and markers of oxidative stress, nitric oxide bioavailability and vitamin E levels were measured. Flow-mediated dilatation (FMD) was also measured.
Results: Smoking both electronic cigarettes and traditional cigarettes led to a significant increase of the levels of sNox2-dp, 8-isoPGF2α and to a significant decrease of NO bioavailability, vitamin E levels and FMD. Generalizing estimating equation analysis confirmed that all markers of oxidative stress and FMD were significantly affected by smoking and showed that the biologic effects of electronic cigarettes versus traditional cigarettes on vitamin E levels (p=0.413) and FMD (p=0.311) were not statistically different. On the other hand, electronic cigarettes appeared to have a lesser impact than traditional cigarettes on levels of sNox2-dp (p=0.001), 8-isoPGF2α (p=0.046) and NO bioavailability (p=0.001).
Conclusions: Our study demonstrates that both cigarettes have unfavorable effects on markers of oxidative stress and FMD after single use, although E-cigarette appeared to have a lesser impact. Future studies are warranted to clarify the chronic vascular effects of E-cigarette smoking.

The full reference is  Carnevale R, Sciarretta S, Violi F, Nocella C, Loffredo L, Perri L, Peruzzi M, Marullo AGM, De Falco E, Chimenti I, Valenti V, Biondi-Zoccai G, Frati G, Acute impact of tobacco versus electronic cigarette smoking on oxidative stress and vascular function, CHEST (2016), doi: 10.1016/j.chest.2016.04.012.

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