People with cerebral amyloid angiopathy more likely to develop dementia

Cerebral amyloid angiopathy (CAA) is a condition where protein (called amyloid) builds up in the brain, making blood vessels weak. People with CAA are four times more likely to develop dementia within five years, regardless of whether they have had a stroke, according to a preliminary study to be presented at the American Stroke Association's International Stroke Conference 2026. The meeting is in New Orleans, Feb. 4-6, 2026, and is a world premier global event dedicated to advancing stroke and brain health science.

Cerebral amyloid angiopathy (CAA) can lead to hemorrhagic stroke (bleeding stroke) and raises the risk of ischemic stroke (clot-caused stroke). As people age, some amyloid protein can collect in the brain's blood vessels without causing symptoms. People receive a clinical diagnosis of CAA when the buildup becomes significant enough to damage the vessels and affect brain function. In some severe cases, the protein deposits can cause the walls of blood vessels to crack. This can lead to blood leaking out and damaging the brain, and this damage is known as a bleeding or hemorrhagic stroke. CAA also contributes to cognitive impairment and is often found in people with Alzheimer's Disease. This study investigated the risk of developing dementia among adults diagnosed with CAA, the link between CAA and stroke and the risk of dementia.

Many people with CAA develop dementia; however, so far, clinicians haven't had clear, large-scale estimates on how often and how quickly dementia progresses in these patients." 

Samuel S. Bruce, M.D., M.A., study author, assistant professor of neurology, Weill Cornell Medicine, New York City

"Our study calculated estimates from a large sample of Medicare patients whether people with CAA are more likely to be newly diagnosed with dementia and to clarify how CAA and stroke - separately and together - relate to new dementia diagnoses."

Researchers analyzed the health information for more than 1.9 million adults covered by Medicare, ages 65 and older, from 2016 to 2022. They reviewed newly diagnosed dementia cases and how ischemic and hemorrhagic stroke are related to dementia risk in people with CAA. Patients were tracked through health changes - no CAA or stroke, CAA only, stroke only, both CAA and stroke - over time. By observing health status over time, the researchers could see how much time each patient spent in each state and pinpoint the onset of dementia, Bruce explained.

They found that CAA greatly increased the risk of developing dementia within the 5-year estimate, even more than the effects of stroke.

The analysis found:

• The risk of being diagnosed with dementia within five years of CAA diagnosis was about four times higher in people with CAA versus people without CAA (42% vs. 10%, respectively).
• People with CAA and stroke were 4.5 times more likely to be diagnosed with dementia at any given time point, compared to adults with neither CAA nor stroke.
• People with CAA without stroke were 4.3 times more likely to be diagnosed with dementia at any given time point, compared to patients with neither CAA nor stroke.
• Adults with only stroke without CAA were 2.4 times more likely to be diagnosed with dementia at any given time point, compared to patients with neither CAA nor stroke.

"What stood out was that the risk of developing dementia among those with CAA without stroke was similar to those with CAA with stroke, and both conditions had a higher increase in the incidence of dementia when compared to participants with stroke alone. This suggests that non-stroke-related mechanisms are instrumental to dementia risk in CAA," Bruce said. "These results highlight the need to proactively screen for cognitive changes after a diagnosis of CAA and address risk factors to prevent further cognitive decline."

According to Steven M. Greenberg, M.D., Ph.D., FAHA, former chair of the International Stroke Conference and author of the commentary, Cerebral Amyloid Angiopathy | Stroke, "Diseases of the brain's small blood vessels are major contributors to dementia. This is especially true for CAA, which often occurs together with Alzheimer's disease, making for a potent 1-2 punch. We know there is risk for dementia after any type of stroke, but these results suggest even greater risk for CAA patients." Greenberg is also a professor of neurology at Harvard Medical School in Boston and was not involved in this study.

Study limitations included that researchers obtained clinical study information from administrative diagnosis codes used in inpatient and outpatient health insurance claims submitted to Medicare. "These codes are an imperfect proxy for clinical diagnoses, and misclassifications can occur," Bruce said. Researchers tried to mitigate the limitation by using codes that have been shown to accurately capture correct diagnoses in administrative data. They also did not have access to imaging data to more rigorously assess the diagnoses of CAA and stroke.

Further research is needed to confirm these results, especially with prospective studies that follow patients forward (instead of looking back in time). Those studies should include standardized approaches for diagnosing CAA and stroke.

Study details, background and design:

• This retrospective study, which examined past data, included information from both inpatient and outpatient health claims for 1,909,365 adults in the U.S. covered by Medicare. Of those, 752 (0.04%) received a CAA diagnosis during the study period.
• Participants were age 65 and older, with an average age of 73 years; 54% were women and 46% were men. The participants were 82.4% white adults, 7.3% Black adults, and 10.3% were individuals from other racial groups.
• The study used data collected by Medicare on health insurance claims submitted by professionals and hospitals in the course of clinical care. Researchers had access to multiple years of data, from 2016 to 2022.