The risk of developing dementia is significantly higher within a year of surviving a stroke, a new study using data from Ontario suggests.

Researchers examined a database at the University of Toronto’s Institute for Clinical Evaluative Sciences. They identified over 180,000 people who suffered a stroke and matched the survivors to two control groups: people in the general population and those who had a heart attack but not a stroke.

The study, which examined data from 2002 to 2022, found that the risk of dementia was 80 per cent higher in stroke survivors than both the general population and those who had a heart attack.

“Our findings show that stroke survivors are uniquely susceptible to dementia, and the risk can be up to 3 times higher in the first year after a stroke,” said lead study author Raed Joundi, M.D., D.Phil., an assistant professor at McMaster University.

Their research also found that nearly 20 per cent of stroke survivors develop dementia over the next five-and-a-half years. The risk for those who had an intracerebral hemorrhage, or bleeding in the brain, was nearly 150 per cent higher than the general population.

“We found that the rate of post-stroke dementia was higher than the rate of recurrent stroke over the same time period,” Joundi said. “Stroke injures the brain including areas critical for cognitive function, which can impact day-to-day functioning. Some people go on to have a recurrent stroke, which increases the risk of dementia even further, and others may experience a progressive cognitive decline similar to a neurodegenerative condition.”

Five years after suffering a stroke, the risk of dementia dropped to a rate of 1.5 times higher than the general population. While the risk continues to decrease over time, it remained elevated for up to 20 years after a stroke.

Joundi, an investigator at the Population Health Research Institute, a joint venture between McMaster and Hamilton Health Services, said the findings reinforce the importance of monitoring people with stroke for cognitive decline, and should encourage people to make lifestyle changes, such as quitting smoking and increased physical activity.

“More research is needed to clarify why some people who have a stroke develop dementia and others do not,” she said.

The research will be presented at the 2024 American Stroke Association’s International Stroke Conference, which will be held in Phoenix, Ariz. between Feb. 7 and 9. This is the world premiere meeting for researchers and clinicians dedicated to the science of stroke and brain health, according to the American Heart Association.