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The use of e-cigarettes is associated with an increased risk of heart attack, stroke and stroke, according to research to be presented on February 6 at the American Stroke Association International Conference in Honolulu.
Concerns over the impact of the use of electronic cigarettes on health have increased in recent years, due to their growing popularity and the belief that they are safe alternatives to regular cigarettes.
The use of e-cigarettes 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 one in 5 high school students, were e-cigarette users, according to the Center for Disease Control and Prevention.
"There is a certain notion that e-cigarettes are harmless," says Dr. Paul Ndunda, author of the study and assistant professor at the University of Kansas Medical School in Wichita. "But this study and previous studies show that although they are less harmful than normal cigarettes, their use comes at risk."
Researchers used the data collected by the 2016 risk-monitoring system, a telephone survey sponsored by several federal agencies, including the CDC. The survey includes people in all 50 states who ask for risky health-related behaviors such as smoking and whether respondents have been diagnosed with any health problems.
Of the more than 400,000 respondents reported in 2016, 66,795 patients who used e-cigarettes at least once and compared to non-established e-cigarette users had 71 percent higher stroke risk, 59 percent higher risk of heart attack and 40 percent higher risk heart disease.
Ndunda says the nature of the analysis prevented the research team from accurately calculating the absolute risk of heart attack and stroke from the database.
Conclusions were not published in the reviewed scientific journal, but Ndunda says researchers are planning to present their results soon.
"These results are important because they qualitatively and quantitatively agree with previous studies," says Stanton Glantz, a researcher of tobacco and electronic cigarettes at the University of California, San Francisco, who did not take part in this work but published another study – the risk of heart attack. "The fact that the risk factors for stroke and heart attack are not so different is also the same pattern you see when smoking cigarettes, which adds extra weight to this study."
However, many e-cigarette users also smoke conventional cigarettes.
Indeed, Ndunda found that e-cigarette users are twice as likely to smoke conventional cigarettes as compared to people who do not use e-cigarettes.
To see the health effects of using cigarettes alone, Ndunda and his colleague Dr. Tabitha Muutu compared people who only used electronic cigarettes – not conventional cigarettes – for non-smokers.
"Even in this group there was 29 percent more stroke risk and 25 percent higher risk of heart attack," says Ndunda. Together, these two analyzes point to the additive effect of using cigarettes and conventional cigarettes.
"So if you are a dual user, which is a lot of e-cig users, it's really worse," says Glantz, who found a similar additive effect in his study.
Scientists are not entirely sure how electronic cigarettes lead to this higher risk.
E-cigarette smoking can contribute to the gradual accumulation of fatty deposits in the arteries, says Glantz. But they think researchers can uncover the link between increased risk of heart attacks and blood vessels and e-cigarettes because they have an immediate effect on the cardiovascular system.
You could have this existing kit, says Glantz, "and then you use an e-cigarette and trigger a lot of inflammatory processes, release of oxidizing agents and things that then interfere with the normal functioning of blood and blood vessels, causing a heart attack or stroke."
"This study has some limitations," says Ndunda. One of these studies did not distinguish between occasional use of electronic cigarettes and those who behave more often. "It probably depends on how much you use and we could not evaluate it," says Ndunda.
E-cigarettes can deliver a range of nicotine concentrations and a wide range of flavor chemicals, adding further complications to the analysis. The study project also means that it can only show the link between the use of e-cigarettes and the risk, not the cause and effect.
Ndunda added that a study that identifies e-cigarette users in a timely manner and then monitors their health over time would provide a clearer picture of the consequences of the flow.
Doctor Chitra Dinakar, a clinical professor of pulmonary and critical care at Stanford University Medical School who researched the health effects of e-cigarettes, says that this work, which only carries adults 18 years of age, "does not reflect the risk of stroke in younger users." , "this is an important topic that deserves continuous control."
Jonathan Lambert is an intern at the NPR's Science Desk. You can watch it on Twitter: @evolambert.