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Stroke survivors more likely to make dangerous driving errors

Toronto, February 11, 2015

By Leslie Shepherd

Kristin A. Vesely (l) and Megan A. Hird
Kristin A. Vesely (l) and Megan A. Hird

Drivers who have had recent strokes are more likely to make errors during complex driving tasks than drivers who have not had strokes, according to two studies that St. Michael’s Hospital researchers presented today at the American Stroke Association’s International Stroke Conference 2015.

Current guidelines recommend that people should refrain from driving for at least one month after a stroke. However, many patients resume driving sooner, said Megan A. Hird, a researcher in the Neuroscience Research Program of the hospital’s Keenan Research Centre for Biomedical Sciences and author of one of the abstracts. Previous studies suggest that few stroke patients receive driving advice from their physician before being sent home from hospital.

Hird and her colleagues compared the driving performance of 10 patients seven days after they had mild ischemic strokes with 10 people similar in age and education who had not had a stroke.

Using driving simulation technology, participants completed several driving tasks, from routine right and left turns to more demanding left turns with traffic, where most accidents occur, and a bus-following task, requiring sustained attention.

They found:

  • Stroke survivors committed more than twice as many driving errors.
  • Stroke survivors had more errors during left turns with traffic and were almost four times more likely to make driving mistakes during the bus following task.

“Driving is a complex and multifaceted task,” said Hird, who is also a master’s student at University of Toronto. “Our study suggests that even patients with mild deficits may experience driving impairment, particularly during more cognitively demanding driving situations. More research is required to better characterize the driving performance of patients after stroke, so that healthcare professionals can better assess when it’s safe for stroke patients to resume driving.”

A second study by Kristin A. Vesely reviewed the driving performance of patients who had suffered a type of stroke known as subarachnoid hemorrhages most commonly caused by a ruptured brain aneurysm.

Researchers used driving simulation technology to compare the driving performance of nine functionally independent subarachnoid hemorrhage patients, who had their strokes more than three months prior, to nine healthy volunteers.

“We’ve long known that thinking, decision-making and functional limitations persist despite good recovery among patients who suffer subarachnoid hemorrhage, but researchers and clinicians do not yet understand how these impairments impact real-world activities, such as driving a car,” said Vesely, who is also a researcher in the hospital’s Neuroscience Research Program and a master’s student at the University of Toronto.

They found subarachnoid hemorrhage patients made a greater number of hazardous errors including:

  • They had twice the number of collisions in simulated driving conditions.
  • They were three times more likely to drive outside road lines.
  • They made more errors during the most mentally demanding driving maneuvers, including making left turns and left turns with oncoming traffic. But they did not perform worse than age-matched, healthy drivers at making simpler right turns.

“Today’s physician guidelines for assessing these patients’ driving ability do not provide objective, office-based assessment tools to help physicians identify unsafe drivers,” Vesely said. “Future studies should explore driving ability in a larger group of subarachnoid hemorrhage patients, to more clearly determine driving recommendations post-stroke. We need to understand which clinical characteristics can help predict certain driving impairments, leading to more targeted assessment and rehabilitation programs for individuals who may be able to safely resume driving.”

Both research projects were funded by the Heart and Stroke Foundation of Canada with additional funding for the first study from the Ontario Ministry of Research and Innovation.

About St. Michael's Hospital

St. Michael’s Hospital provides compassionate care to all who enter its doors. The hospital also provides outstanding medical education to future health care professionals in 27 academic disciplines. Critical care and trauma, heart disease, neurosurgery, diabetes, cancer care, care of the homeless and global health are among the hospital’s recognized areas of expertise. Through the Keenan Research Centre and the Li Ka Shing International Healthcare Education Centre, which make up the Li Ka Shing Knowledge Institute, research and education at St. Michael's Hospital are recognized and make an impact around the world. Founded in 1892, the hospital is fully affiliated with the University of Toronto.

Media contacts

For more information, or to arrange an interview with Kristin A. Vesely or Megan A. Hird, please contact:

Leslie Shepherd
Manager, Media Strategy, St. Michael's Hospital
416-864-6094
shepherdl@smh.ca