Researchers from the University of Kansas studied 400,000 Americans who responded to the 2016 Behavioral Risk Factor Surveillance System survey, which is conducted annually by the US Centers for Disease Control and Prevention (CDC).
Out of the 400,000 survey participants, 66,795 revealed that they had smoked e-cigarettes (or "vaped") at least once in their lifetimes. The findings also showed that people who vape had a 71 percent higher risk of stroke and a 59 percent higher risk of heart attack compared to non-users. In addition, people who smoked e-cigarettes had a 40 percent higher risk of coronary heart disease than non-users.
The study, however, only indicated whether the participants were smokers (that is, whether they smoked cigarettes, e-cigarettes or both) or non-smokers. The survey did not differentiate between those who only use e-cigarettes and those who only smoke traditional cigarettes.
E-cigarettes, which are battery-operated devices used to inhale an aerosol, usually containing nicotine, were first introduced to the market in 2004. They are offered in various flavors, including fruit, chocolate and candy, and are popular among young people. According to the CDC, more than one in five high school students were e-cigarette users in 2018.
"There's a certain notion that e-cigarettes are harmless," University of Kansas researcher Paul Ndunda, who was part of the study, told NPR. "But this study and previous other studies show that while they're less harmful than normal cigarettes, their use still comes with risks."
However, he noted that the study was limited, revealing only an association between disease and vaping rather than a causal link.
"This study certainly has limitations," Ndunda says. For example, the study didn't differentiate between occasional e-cigarette users and those who vape more frequently. "It likely matters how much you're using, and we couldn't evaluate that here," Ndunda told NPR.
"This research calls for well-designed, large, long-term population studies to assess whether e-cigarettes cause stroke and cardiovascular disease," he added.
Although the findings have not yet been published in a peer-reviewed scientific journal, the researchers hope to submit their results for review soon.
"These results are important, as they qualitatively and quantitatively agree with previous studies," Stanton Glantz, a tobacco and e-cigarette researcher at the University of California, San Francisco, who wasn't involved in the study, told NPR.
"The fact that the stroke and heart attack risk factors are not that different is also the same pattern you see with cigarette smoking, which adds extra weight to this study too," Glantz added.