A large U.S. study involving nearly 2 million older adults found that cerebral amyloid angiopathy, a condition in which amyloid proteins accumulate in brain blood vessels, is linked to a much higher risk of developing dementia within five years. The increased dementia risk was seen in people with cerebral amyloid angiopathy whether or not they had ever experienced a stroke, showing that the condition itself plays a major role in cognitive decline. Researchers say the results point to the importance of early and routine screening for memory and thinking changes after a diagnosis of cerebral amyloid angiopathy, which could help slow further cognitive decline.

Protein Buildup in Brain Blood Vessels Tied to Dementia Risk

Cerebral amyloid angiopathy (CAA) is a brain disorder in which a protein called amyloid accumulates inside blood vessels, gradually weakening them. A large preliminary study found that people diagnosed with CAA were about four times more likely to develop dementia within five years, even if they had never experienced a stroke. The research will be presented at the American Stroke Association’s International Stroke Conference 2026, which will be held in New Orleans from Feb. 4-6, 2026. The conference is considered a leading international forum for research on stroke and brain health.

How Cerebral Amyloid Angiopathy Damages the Brain

CAA is known to increase the likelihood of hemorrhagic stroke (bleeding stroke) and also raises the risk of ischemic stroke (clot-caused stroke). As part of normal aging, small amounts of amyloid can build up in brain blood vessels without causing noticeable symptoms. A clinical diagnosis of CAA is made when this buildup becomes extensive enough to damage blood vessels and interfere with normal brain function.

In more advanced cases, amyloid deposits can weaken vessel walls to the point that they crack. When this occurs, blood can leak into nearby brain tissue, causing a hemorrhagic stroke. Beyond stroke risk, CAA is also linked to cognitive decline and is commonly found in people with Alzheimer’s Disease. The current study focused on how often dementia develops after a CAA diagnosis and how stroke and CAA together influence dementia risk.

Large Medicare Study Examines Dementia Outcomes

“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,” said study author Samuel S. Bruce, M.D., M.A., an assistant professor of neurology at Weill Cornell Medicine in 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 health records from more than 1.9 million Medicare beneficiaries age 65 and older, covering the years 2016 to 2022. The team reviewed new dementia diagnoses and examined how ischemic and hemorrhagic strokes affected dementia risk among people with CAA.

Participants were followed as their health status changed over time, including periods with no CAA or stroke, CAA alone, stroke alone, or both conditions. Tracking these transitions allowed researchers to measure how long individuals remained in each category and determine when dementia was first diagnosed, Bruce explained.

Dementia Risk Higher Than Stroke Alone

The analysis showed that CAA substantially increased the likelihood of developing dementia within the five-year time frame, with a stronger effect than stroke by itself.

Key findings included:

Within five years of diagnosis, dementia was identified in about 42% of people with CAA, compared with about 10% of people without CAA. Individuals with both CAA and stroke were 4.5 times more likely to receive a dementia diagnosis at any given time point than those with neither condition. Individuals with CAA but no history of stroke were 4.3 times more likely to be diagnosed with dementia at any given time point compared with those who had neither CAA nor stroke. Adults who had experienced stroke without CAA were 2.4 times more likely to be diagnosed with dementia compared with those who had neither condition.

“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.”

Experts Emphasize Role of Small Blood Vessels

Steven M. Greenberg, M.D., Ph.D., FAHA, former chair of the International Stroke Conference and author of the commentary, Cerebral Amyloid Angiopathy | Stroke, said the findings fit into a broader understanding of dementia risk. “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, who is also a professor of neurology at Harvard Medical School in Boston, was not involved in the study.

Study Limitations and Future Research

The researchers noted that the study relied on administrative diagnosis codes from inpatient and outpatient Medicare insurance claims rather than detailed clinical evaluations. “These codes are an imperfect proxy for clinical diagnoses, and misclassifications can occur,” Bruce said. To address this issue, the team used diagnosis codes that have previously been shown to accurately reflect real diagnoses in administrative data. The study also lacked imaging data, which limited the ability to confirm CAA and stroke diagnoses more precisely.

The authors emphasized that additional research is needed, particularly prospective studies that follow patients forward in time rather than relying on historical records. Future work should also use standardized diagnostic methods for both CAA and stroke.

Study Design and Participant Details

This retrospective study analyzed inpatient and outpatient Medicare claims for 1,909,365 adults in the United States. During the study period, 752 individuals (0.04%) received a diagnosis of CAA.

All participants were age 65 or older, with an average age of 73 years. Women made up 54% of the study population, while men accounted for 46%. The group included 82.4% white adults, 7.3% black adults, and 10.3% individuals from other racial groups.

The data were drawn from Medicare health insurance claims submitted by clinicians and hospitals during routine care, spanning multiple years from 2016 to 2022.