Secondhand Smoke Increases Stroke Risk by 30%

Evidence has long established secondhand smoke as a carcinogen, but new research now suggests it may also be a risk factor for stroke. Among nonsmokers, those exposed to secondhand cigarette smoke had a 30% higher risk of stroke than those who weren’t, according to a new study.

“There is much evidence that those who smoke are at higher risk for cardiovascular events and stroke—this extends that research to those who spend time around people who are smoking,” says senior study author Leslie McClure, PhD, a professor in the Department of Biostatisticsat the University of Alabama at Birmingham.

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Using data from the Reasons for Geographic and Racial Differences in Stroke (REGARDS) study, McClure and her colleagues looked at the association of secondhand smoke exposure and risk of stroke among nonsmokers.

Of nearly 22,000 participants, 23% reported secondhand smoke exposure in the past year. Over the course of the 9-year study, 428 study subjects reported having a stroke. A further analysis of stroke subtype revealed that the vast majority of these incidents (352) were ischemic strokes.

Even after the researchers adjusted for other stroke risk factors, the risk of overall stroke was increased by 30% among those who had been exposed to secondhand smoke. They also found there was a dose-response relationship between secondhand smoke exposure and stroke risk—as the amount of exposure time increased, the risk increased.

“We definitely feel that exposure to secondhand smoke is a public health problem, and clearly there have been policy changes that have helped reduce this exposure in public places,” McClure says. “That being said, health care providers should certainly be proactive in encouraging their patients to steer clear of situations in which they’ll be exposed to secondhand smoke.”

She and her colleagues say more research is needed to determine whether secondhand smoke exposure among former smokers further impacts their risk of stroke and to reveal more about the relationship between secondhand smoke exposure and hemorrhagic stroke. In addition, they plan to continue research in this area.

“We are interested in the impact of secondhand smoke exposure in the context of other environmental exposures, such as particulate matter and ozone,” McClure says. “We are also interested in the use of e-cigarettes, which is on the rise, and its association with stroke.”

—Colleen Mullarkey


Malek AM, Cushman M, Lackland DT, Howard G, McClure LA. Secondhand smoke exposure and stroke: The Reasons for Geographic and Racial Differences in Stroke (REGARDS) study. Am J Prev Med. 2015 Jun 16. [Epub ahead of print]