Dementia risk may be 3 times higher in the first year after a stroke

Each year, about 15 million people around the world have a stroke.
Past studies show having a stroke can increase a person’s risk for certain diseases, such as dementia.
Researchers from McMaster University report having a stroke increases a person’s dementia risk by 80%, even after accounting for other dementia risk factors.
Scientists also found dementia risk was three times higher in the first year after a stroke.

Each year, about 15 million people around the world have a stroke — a condition where a blood vessel leading to the brain is blocked or bursts, causing a lack of oxygen to the brain.

Of that number, researchers estimate about half will live with a permanent or chronic disability, such as paralysis on one side of the body, communication difficulties, memory loss, or problems with gripping or holding items.

Past studies also show that having a stroke can increase a person’s risk for diseases such as vision issues, depression, post-stroke fatigue, trouble swallowing, cancer, and dementia.

Now, new research presented at the American Stroke Association’s International Stroke Conference 2024 reports that having a stroke increased a person’s dementia risk by 80%, even after accounting for other dementia risk factors. The findings have yet to be published in a peer-reviewed journal.

Researchers also found dementia risk was three times higher in the first year after a stroke.

This risk decreased to a 1.5-times increased risk by five years after a stroke and remained elevated 20 years later.

During a stroke, the oxygen flow is cut off to the brain. This can result in the death of brain cells, causing dementia. Vascular dementia is a type of dementia caused by reduced blood flow to the brain.

However, past studies show having a stroke can also increase a person’s risk for another type of dementia, known as Alzheimer’s disease, as well as all-cause dementia.

Dr. Raed Joundi is an assistant professor at McMaster University in Hamilton, Ontario, Canada, an investigator at the Population Health Research Institute, a joint institute of McMaster University and Hamilton Health Sciences, an adjunct scientist at ICES, and the lead author of this study.

Dr. Joundi told Medical News Today that the researchers decided to further investigate the link between stroke and increased dementia risk because, with an aging population, more people are experiencing stroke, and an increasing number of people are surviving the consequences of stroke.

“Cognitive impairment is very common after stroke and may lead to dementia, which lowers quality of life and decreases life expectancy. It is important to show a direct link between stroke and dementia, and investigate the timing of dementia after stroke, to inform the research, planning, and delivery of interventions.”

– Dr. Joundi

For this study, Dr. Joundi and his team analyzed data from more than 15 million people in Ontario, Canada through medical databases. About 181,000 people were identified as having either an ischemic stroke (stroke caused by a clot in arteries around the brain) or intracerebral hemorrhage (burst blood vessel in the brain) who survived without dementia for at least 90 days.

The stroke participants were matched to two different control groups — one of people in the general population who had not had a stroke or heart attack, and another group of people who had had a heart attack but not a stroke.

Upon analysis, scientists found dementia risk was 80% higher in people who had a stroke when compared to the control group with no heart attack or stroke. The risk for dementia was almost 80% higher in people who had a stroke when compared to the control group who had a heart attack and no stroke.

“We were able to show that the elevated risk of dementia persisted even after matching to control (comparison) groups with the same age, sex, neighborhood socioeconomic status, and vascular risk factors.

As stroke imposes a direct injury on the brain, which may have an immediate impact but also long-term impacts on brain function, this result is not entirely surprising but important to confirm through this large and robust analysis.”

– Dr. Joundi

Additionally, the researchers discovered dementia risk was almost three times higher in the first year following a stroke. The risk declined to a 1.5-times increased risk by the five-year mark following a stroke and remained elevated 20 years later.

“We found a three-fold risk of dementia between three and 12 months after stroke,” Dr. Joundi explained. “The first three months after stroke were not included as it is usually too early to make a definitive diagnosis of dementia.”

“The presence of a higher risk of dementia earlier after stroke is not too surprising, since there is a direct brain injury from the stroke which can impact cognition and daily function, and physicians are following up closer with patients in the first year and therefore more likely to make a diagnosis of dementia,” he continued. “The more surprising aspect was that the increased risk of dementia persisted throughout 20 years of follow-up, compared to matched controls, so there are many indirect mechanisms that may be acting long-term to promote a higher risk of dementia after stroke.”

After reviewing this study, Dr. Cheng-Han Chen, a board-certified interventional cardiologist and medical director of the Structural Heart Program at MemorialCare Saddleback Medical Center in Laguna Hills, CA, told MNT that this study demonstrates the elevated risk for stroke victims to develop dementia, a risk that is markedly high, even higher than the risk of developing another stroke.

“This study highlights the importance of discussing with stroke patients and their family members the increased risk of developing dementia. These patients will need to be monitored carefully for evidence of cognitive decline, and medication and lifestyle modifications should be initiated to reduce their risk.”

– Dr. Chen

MNT also discussed the study with Dr. José Morales, a vascular neurologist and neuro-interventional surgeon at Pacific Neuroscience Institute in Santa Monica, CA.

Dr. Morales said he was surprised by how much higher a dementia risk was found in the study compared to prior studies.

“It really provides added emphasis on the idea of doing everything we can to prevent stroke, by either primary prevention through lifestyle changes or secondary prevention with medical management to optimize their vascular risk factors,” he added.

Read the full article here