A preliminary study of nearly 2 million Medicare beneficiaries has found that cerebral amyloid angiopathy (CAA) — a condition characterized by the buildup of amyloid proteins in the brain's blood vessels — is associated with a fourfold increased risk of developing dementia within five years, regardless of whether a person has had a stroke. The research, to be presented at the American Stroke Association's International Stroke Conference 2026 in New Orleans, provides large-scale estimates of dementia progression in patients with CAA, a condition previously linked to cognitive decline and Alzheimer's disease.
Researchers analyzed health data from 2016 to 2022 for adults aged 65 and older covered by Medicare, tracking new dementia diagnoses and the relationship between ischemic and hemorrhagic stroke and dementia risk in people with CAA. Among 1,909,365 participants, 752 (0.04%) received a CAA diagnosis during the study period. The analysis revealed that the five-year dementia risk was 42% for those with CAA versus 10% for those without. People with CAA and stroke were 4.5 times more likely to be diagnosed with dementia at any given time compared to those with neither condition, while those with CAA alone were 4.3 times more likely. In contrast, stroke alone increased dementia risk by 2.4 times.
"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," said study author Samuel S. Bruce, M.D., M.A., assistant professor of neurology at Weill Cornell Medicine in New York City. "This suggests that non-stroke-related mechanisms are instrumental to dementia risk in CAA." Bruce emphasized the need to proactively screen for cognitive changes after a CAA diagnosis and address risk factors to prevent further decline.
Steven M. Greenberg, M.D., Ph.D., FAHA, former chair of the International Stroke Conference and author of a commentary on CAA, noted that 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," said Greenberg, a professor of neurology at Harvard Medical School who was not involved in the study. "We know there is risk for dementia after any type of stroke, but these results suggest even greater risk for CAA patients."
Study limitations include the use of administrative diagnosis codes, which may not perfectly capture clinical diagnoses, and the lack of imaging data to rigorously confirm CAA and stroke diagnoses. The researchers used codes shown to accurately capture diagnoses in administrative data to mitigate misclassification. Further prospective studies with standardized diagnostic approaches are needed to confirm these findings.
The study highlights the importance of monitoring cognitive health in older adults with CAA. As the American Heart Association's 2026 Heart Disease and Stroke Statistics notes, stroke is now the fourth leading cause of death in the U.S., and conditions like CAA may compound the burden of cognitive decline. The findings underscore the need for clinicians to consider dementia risk when managing patients with cerebral amyloid angiopathy.
