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The use of e-cigarettes is associated with an increased risk of heart attack, heart disease, and stroke, according to a survey to be presented on February 6 at the American Association of American Brain Conjunctures in Honolulu.
Concerns about the health effects of e-cigarette use have increased in recent years, fueled by increased popularity and the belief that they are safe alternatives to normal cigarettes.
The use of e-cigarettes among high school students increased by 900 per cent between 2011 and 2015. In 2018, more than 3.6 million young people in the United States, including 1 in 5 high school students, were e-cigarette users, according to the Centers for Disease Control and Prevention.
"There is a certain assumption that e-cigarettes are harmless," says Dr. Paul Nunda, author of the study and assistant professor at the Medical School at the University of Kansas in Wichita. "But this study and previous studies show that although they are less harmful than normal cigarettes, their use still comes with risks."
The researchers used data collected by the risk monitoring system from the risk behavior of 2016, a telephone survey sponsored by several federal agencies, including the CDC. The survey includes people in all 50 countries, asking for risky health-related behavior, such as smoking, and whether the respondents are diagnosed with health problems.
Of the over 400,000 respondents in 2016, 66,795 reported using e-cigarettes at least once and compared to those who did not use, e-cigarette users had a 71 percent higher risk of stroke, a 59 percent higher risk of heart attack, and 40 a higher risk of heart disease.
Nunda says the nature of the analysis prevented the research team from accurately calculating the absolute risk of heart attack and stroke from the database.
Findings have not been published in peer-reviewed scientific journals, but Ndunda says researchers plan to submit their results soon.
"These results are important because they qualitatively and quantitatively agree with previous studies," said Stanton Glancz, a tobacco and e-cigarette researcher at the University of California, San Francisco, who was not involved in this work, but published another study which connects e-use of cigarettes for a greater risk of heart attack. "The fact that risk factors for stroke and heart attack are not so different is also the same pattern you see with smoking cigarettes, which further increases this study."
However, many e-cigarette users smoke conventional cigarettes.
In fact, Ndunda believes that e-cigarette users are twice as likely to smoke conventional cigarettes as compared to people who do not use e-cigarettes.
To see health effects only on the use of e-cigarettes, Ndunda and colleague Dr. Tabitha Muutu compared people who used only cigarettes – not conventional cigarettes – to non-smokers.
"Even in that group there was a higher risk of stroke by 29 percent and a 25 percent higher risk of heart attack," said Nunda. Taken together, these two analyzes point to the added effect of e-cigarettes and the conventional use of cigarettes.
"So, if you are a dual user, who is a lot of e-reader users, you are actually worse," said Glancz, who found a similar additional effect in his study.
Scientists are not quite sure how e-cigarettes lead to this higher risk.
Smoking cigarettes can contribute to a gradual increase in fatty deposits in the arteries, Glanc says. But he thinks the researchers may discover a link between the increased risk of heart attacks and strokes and the use of e-cigarettes due to a faster effect on the cardiovascular system.
You can have this pre-existing build, says Glancz, "then use the e-cigarette and it causes many inflammatory processes, the release of oxidizing agents and things that then interfere with the normal functioning of the blood and blood vessels and it causes a heart attack or stroke. "
"This study certainly has limitations," says Nunda. For one, this study could not distinguish between the occasional use of e-cigarettes and those who often hesitate. "It's probably important how you use it, and we were not able to appreciate that," Nunda said.
E-cigarettes can deliver a range of nicotine concentrations and a wide range of chemical aromas, adding further complications in the analysis. The design of the study also means that it can show only an association between the use of e-cigarettes and the risk, not the cause and effect.
Ndunda added that a study that identifies e-cigarette users early, and then monitors their health over time, will give a clearer picture of the consequences of the extraction.
Dr Chitra Dinacar, a clinical professor of lung and critical care medicine at Stanford Medical School, who studied the health effects of e-cigarettes, says this work, which only explores adults 18 and older, "does not reflect the risk from a stroke among younger users. "However, she says," this is an important topic that deserves ongoing supervision. "
Jonathan Lambert is an intern at the NPR's scientific office. You can follow it on Twitter: @evolambert.