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The use of e-cigarettes is associated with increased risk of heart attack, heart disease and stroke, according to research that is scheduled to be presented Feb. 6 at the American Stroke Association's International Stroke Conference in Honolulu
Concern about the health effects of e-cigarette use has grown in recent years, fueled by a surge in their popularity and a belief that they are safe alternatives to normal cigarettes .
E-cigarette use among high school students increased by 900 percent between 2011 and 2015. In 2018, more than 3.6 million young people in the US, including 1 in 5 high school students, were users of e-cigarettes, according to the Centers for Disease Control and Prevention
"There is a certain notion that e-cigarettes are harmless," says Dr. Paul Ndunda, the study's author and assistant professor at the School of Medicine at the University of Kansas in Wichita. "But this study and previous studies show that while they are less harmful than normal cigarettes, their use still comes with risks."
The researchers used data collected by the 2016 Behavioral Risk Factor Surveillance System, a telephone survey sponsored by several federal agencies, including the CDC. The survey includes people in all 50 states, asking about risky health-related behaviors, such as smoking, and whether respondents have been diagnosed with any health problems
Of the over 400,000 respondents in 2016, 66,795 reported having used e-cigarettes at E-cigarette users had a 71 percent higher risk of stroke, a 59 percent higher risk of heart attack, and a 40 percent higher risk of heart disease.
Ndunda says that the nature of the analysis prevented the research team from accurately calculating the absolute risk of heart attack and stroke from the database.
"These results are important, as they qualitatively and quantitatively agree with previous studies," says Ndunda, who is planning to submit their results soon
. Stanton Glantz, and a tobacco and e-cigarette researcher at the University of California, San Francisco, who was not involved in this work but published another study that linked e-cigarette use to a higher risk of heart attack. "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."
However, many e cigarette users also smoke conventional cigarettes
In fact, Ndunda found that e-cigarette users are twice as likely to smoke conventional cigarettes, compared to people who do not use e-cigarettes. Ndunda and his colleague Dr. Tabitha Muutu compared people who had only used e-cigarettes – not conventional cigarettes – to nonsmokers
"Even in that group there was a 29 percent higher risk of stroke and a 25 percent higher risk of heart attack," says Ndunda. Taken together, these two analyzes point to an additive effect of e-cigarette and conventional cigarette use.
"So if you're a dual user, which many e-cig users are, you're actually worse off," says Glantz, who found a similar additive effect in his study. sure how e-cigarettes lead to this higher risk.
E-cigarette smoking may contribute to the gradual build-up of fatty deposits in arteries, Glantz says. But he thinks researchers may be detecting a link between increased risk for heart attacks and strokes and e-cigarette use because of a more immediate effect on the cardiovascular system
You could have this pre-existing build up, Glantz says, and then you use the e-cigarette and that triggers a bunch of inflammatory processes, the release of oxidizing agents and things that then interfere with the normal functioning of the blood and blood vessels and that triggers a heart attack or stroke. "
" This study certainly has limitations, "says Ndunda. For one, this study could not distinguish between occasional e-cigarette use and those who take more often. "It probably matters how much you're using, and we could not evaluate that here," says Ndunda.
E-cigarettes can deliver a range of nicotine concentrations and a wide variety of chemical flavorings, adding further complications to the analysis. The study's design also means that it can only show an association between e-cigarette use and risk, not cause and effect.
Ndunda added that a study that identifies e-cigarette users early and then tracks their health over time would yield a clearer picture of the consequences of vaping. Chitra Dinakar, a clinical professor of pulmonary and critical care medicine at Stanford University School of Medicine who has studied the health effects of e-cigarettes, says this work, which only surveys adults 18 and older, "does not reflect the risk of stroke in younger users. " Still, she says, "This is an important subject that merits ongoing scrutiny."
Jonathan Lambert is an intern on NPR's Science Desk. ]