A large national study found that dementia risk increased as stroke severity increased.
People with the most severe strokes had five times higher odds of developing dementia than those who did not have a stroke.
Researchers also found that stroke survivors experienced faster declines in memory, thinking skills, and executive function over time.
A new study from researchers at Michigan Medicine suggests that the severity of a stroke may play a major role in long-term brain health.
According to findings published in JAMA Network Open, people who experience more severe strokes appear to face a much greater risk of cognitive decline and dementia in the years that follow.
“Stroke severity strongly affects thinking and memory after stroke,” senior author Deborah A. Levine, M.D., M.P.H., said in a news release.
“Our findings highlight the need to closely monitor cognition and aggressively treat dementia risk factors in all stroke survivors, especially those with severe strokes.”
The study
To conduct the study, researchers analyzed health data from more than 42,000 adults in the United States, including roughly 1,500 stroke survivors. Participants came from three large long-term research cohorts and were followed for as long as 30 years. The study focused specifically on ischemic strokes, which occur when blood flow to the brain is blocked.
The research team examined how stroke severity related to later changes in cognitive performance and dementia diagnoses. They evaluated several aspects of cognition, including memory, executive function, and overall mental performance. Stroke severity was categorized from minor to severe, allowing researchers to compare outcomes across different levels of impairment.
Researchers also accounted for a variety of factors that could affect brain health, including age and other health conditions. According to the study authors, this helped them better isolate the relationship between stroke severity and long-term cognitive decline. The investigation was observational, meaning it identified associations rather than proving that strokes directly caused dementia.
The results
The results showed a clear pattern: dementia risk rose alongside stroke severity. Compared with people who did not experience a stroke, dementia risk was about twice as high after a minor stroke, roughly three times higher after a moderate stroke, and five times higher after a severe stroke.
Stroke survivors also showed faster declines in thinking abilities over time than people who had not experienced strokes. On average, researchers found that survivors of mild-to-moderate stroke showed cognitive decline similar to being about 1.8 years older at baseline, while survivors of moderate-to-severe stroke declined as if they were approximately 2.6 years older cognitively.
The researchers say several biological factors may help explain the connection, including structural brain damage, inflammation, and neurodegeneration.
Moving forward, the team encourages consumers to maintain overall physical health to help boost long-term cognitive health.
"The best ways to prevent poststroke dementia and cognitive decline are to prevent first and second strokes,” Dr. Levine said.
“That means controlling blood pressure, glucose, and cholesterol to optimal levels, and taking an anticoagulant when atrial fibrillation is present, as recommended.”