Smokers who swap some traditional cigarettes for the electronic kind may not be doing anything to protect their arteries, a new study hints.
People who smoke sometimes use "e-cigarettes" in a bid to get a nicotine fix without inhaling tobacco. But little is known about the effects of e-cigarettes on the risk of heart disease -- the top killer of smokers.
That's because heart disease develops over many years, and vaping is a relatively new phenomenon, explained study author Andrew Stokes, an assistant professor at Boston University School of Public Health.
So, his team decided to look at a more immediate question: Do certain biological markers of heart disease risk differ between smokers and those who use both cigarettes and e-cigarettes?
Specifically, the researchers looked at blood levels of substances that indicate ongoing inflammation or oxidative stress -- a sign of cell damage.
Those processes are key contributors to heart disease in smokers, explained Stokes. Overall, his team found, levels of those biomarkers were comparable in smokers and dual users alike.
According to Stokes, the finding casts doubt on the idea that smokers can benefit from replacing some daily cigarettes with the electronic version.
"Dual use doesn't seem to be an effective way to reduce risk," he said.
It's not clear why. But, Stokes noted, some smokers use e-cigarettes just for "convenience" -- vaping only in situations where traditional smoking is not acceptable.
Other smokers do use e-cigarettes as a way to cut down on tobacco smoking. But that moderate reduction, Stokes said, might not be enough to mitigate the damage of traditional smoking.
Then there's the question of whether e-cigarettes, by themselves, contribute to inflammation and oxidative stress. Lab research has indicated that they can.
But in this study, adults who said they used only e-cigarettes, and not traditional ones, showed no signs of heightened inflammation and oxidative stress: Their biomarker levels were similar to those of adults who did not smoke or vape.
It was a surprising finding, Stokes said. But it does not prove that e-cigarettes are safe for the heart, he stressed.
Dr. Joseph Wu, a volunteer with the American Heart Association, agreed. He was not part of the study.
Only a small number of study participants were vaping exclusively, said Wu, who also directs the Stanford Cardiovascular Institute in California. That, he explained, may have made it harder to detect an effect on the five biomarkers the researchers assessed.
Still, "this is an important exploratory study that will likely lead to many other studies in the future," Wu said.
The findings, published Jan. 4 in the journal Circulation, were based on 7,130 U.S. adults taking part in a long-term health study.
In all, about 59% said they had not smoked or vaped in the past month. Another 30% had smoked, while 10% had smoked and vaped. Just under 2% said they'd only used e-cigarettes.
On average, smokers and dual users showed similar blood levels of the five biomarkers. And both groups looked worse relative to non-users. People who exclusively vaped, on the other hand, looked similar to non-users.
Stokes said it all raises the possibility that smokers could benefit if they switched entirely to e-cigarettes.
But that comes with important caveats. E-cigarettes deliver a hefty dose of nicotine, and there is no evidence, Stokes noted, that they serve as a "bridge to quitting" for smokers.
"What's the end game?" Stokes said. "Will people just trade one addiction for another?"
Beyond that, there is still much to learn about the health effects of e-cigarettes. The battery-powered devices work by heating a liquid that contains various chemicals, including propylene glycol, glycerol and flavorings. The heating creates a "vapor" that is inhaled.
Research has shown that the vapor can harbor toxic substances like heavy metals and tiny particles that can be inhaled deeply into the lungs, according to the U.S. Centers for Disease Control and Prevention.
"There are many constituents [of e-cigarettes] that haven't been scientifically well-characterized yet," Stokes cautioned.
His advice to smokers is to work with their doctor on a plan for quitting. If that involves using e-cigarettes for a time, it should be part of a broader approach to ultimately kicking nicotine addiction, Stokes said.
The Office of the U.S. Surgeon General has more on e-cigarettes.
SOURCES: Andrew Stokes, PhD, assistant professor, global health, Boston University School of Public Health, Boston; Joseph Wu, MD, PhD, American Heart Association volunteer and director, Stanford Cardiovascular Institute, Stanford University School of Medicine, Stanford, Calif.; Circulation, Jan. 4, 2021, online