Risk of dementia nearly 3 times higher first year after stroke: Study

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Having a stroke could significantly increase the risk of developing dementia — particularly during the first year, but for as long as 20 years after the stroke, new research suggests.

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The preliminary research will be presented at the American Stroke Association’s International Stroke Conference, a world premier meeting for researchers and clinicians dedicated to the science of stroke and brain health, later this week in Phoenix, Ariz.

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“Our findings show that stroke survivors are uniquely susceptible to dementia, and the risk can be up to three times higher in the first year after a stroke. While the risk decreases over time, it remains elevated over the long-term,” said lead study author, Dr. Raed Joundi, an assistant professor at McMaster University in Hamilton, and an investigator at the Population Health Research Institute.

To evaluate dementia risk after stroke, researchers used databases at U of T’s Institute for Clinical Evaluative Sciences, which includes information about more than 15 million people in Ontario.

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They identified 180,940 people who had suffered a recent stroke and matched those survivors to two control groups: People in the general population who had not had a heart attack or stroke, and those who had a heart attack, but not a stroke.

Researchers evaluated the rate of new cases of dementia starting at 90 days after stroke over an average follow-up of 5 1/2 years. In addition, they analyzed the risk of developing dementia in the first year after the stroke and over time, up to 20 years.

The study found that the risk of dementia was highest in the first year after stroke, with a nearly three-fold increased risk, then decreasing to a 1.5-fold increased risk by the five-year mark and remaining elevated 20 years later.

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Dementia occurred in nearly 19% of stroke survivors over an average follow-up of 5 1/2 years.

The risk of dementia was 80% higher in stroke survivors than in the matched group from the general population. The risk of dementia was also nearly 80% higher in stroke survivors than in the matched control group who had experienced a heart attack.

The risk of dementia in people who had a type of stroke caused by an intracerebral hemorrhage (bleeding in the brain) was nearly 150% higher than those in 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.”

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