Smoking linked to unexplained strokes in younger adults

Smoking, particularly heavy smoking, is linked to some unexplained strokes in younger adults, mainly in male individuals and in people ages 45 to 49, according to a study published in the February 19, 2025, online issue of Neurology^® Open Access, an official journal of the American Academy of Neurology.

A stroke with no known cause, called a cryptogenic stroke, is a type of ischemic stroke caused by a blockage of blood flow, but it is unclear what has caused the blockage. Symptoms include weakness, trouble speaking and vision problems. Strokes can be fatal. Most strokes occur after age 65.

While smoking has long been linked to ischemic stroke, little is known about how smoking affects people under 50, especially in those with unexplained stroke. Recent research has shown an increase in younger people having these unexplained strokes, so it is important to evaluate any potential links. Our study found that smoking may be a key factor.”

Phillip Ferdinand, MBChB MRCP, of Keele University in the United Kingdom and member of the American Academy of Neurology

For the study, researchers looked at 546 people ages 18 to 49 who had an unexplained stroke. They were matched for age and sex with 546 people who did not have stroke.

Participants answered questions about their smoking habits, alcohol use, education level, physical inactivity and other health conditions. Researchers reviewed responses to determine which factors may be linked to unexplained stroke.

Researchers found that people who had an unexplained stroke were more likely to smoke. Of those with unexplained stroke, 33% smoked compared to 15% of those who didn’t have a stroke.

After adjusting for factors that could affect risk of stroke such as education level, alcohol use and blood pressure, researchers found that people who smoked had more than twice the risk of having unexplained stroke when compared to those who did not smoke. They also found the risk was highest in male participants who had more than three times the risk, and also in people ages 45 to 49 who had nearly four times the risk.

Researchers also looked at smoking intensity, how many cigarettes a person smoked a day. People who smoked the equivalent of more than 20 packs a year had more than four times the risk of unexplained stroke compared to those who did not smoke. This risk was especially high in male participants with nearly seven times the risk, and in people ages 45 to 49 who had nearly five times the risk.

“Our findings suggest that continued public health efforts around preventing smoking, especially heavy smoking, may be an important way to help reduce the number of strokes happening to young people,” said Ferdinand.

A limitation of the study was that it primarily looked at people of white European backgrounds, so the results may not be the same for other populations.

The study was supported by the Helsinki and Uusimaa Hospital District, Academy of Finland, University of Helsinki and Sahlgrenska University Hospital.