A preliminary study analyzing nearly 2 million Medicare patients has found that cerebral amyloid angiopathy (CAA), a condition characterized by amyloid protein accumulation in brain blood vessels, is associated with a fourfold increased risk of developing dementia within five years. The research, to be presented at the American Stroke Association's International Stroke Conference 2026, indicates this elevated risk persists regardless of stroke history, suggesting non-stroke mechanisms significantly contribute to cognitive decline in CAA patients.
The retrospective analysis examined health claims data from 1,909,365 adults aged 65 and older covered by Medicare from 2016 to 2022. Among these participants, 752 (0.04%) received a CAA diagnosis during the study period. Researchers tracked patients across different health states—no CAA or stroke, CAA only, stroke only, and both CAA and stroke—to assess dementia onset. The findings revealed that 42% of people with CAA were diagnosed with dementia within five years of their CAA diagnosis, compared to only 10% of those without CAA.
Notably, the study found that CAA's association with dementia risk was stronger than that of stroke alone. 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 condition, while those with stroke alone were 2.4 times more likely. The risk was highest for individuals with both CAA and stroke, who were 4.5 times more likely to develop dementia. "What stood out was that the risk of developing dementia among those with CAA without stroke was similar to those with CAA with stroke," said study author Samuel S. Bruce, M.D., M.A., an assistant professor of neurology at Weill Cornell Medicine. "This suggests that non-stroke-related mechanisms are instrumental to dementia risk in CAA."
CAA is known to weaken brain blood vessels, potentially leading to hemorrhagic stroke (bleeding stroke) and increasing the risk of ischemic stroke (clot-caused stroke). The condition often coexists with Alzheimer's disease, compounding cognitive impairment. According to Steven M. Greenberg, M.D., Ph.D., FAHA, former chair of the International Stroke Conference and author of a commentary in 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."
The study's implications are significant for clinical practice, as it underscores the necessity for proactive cognitive monitoring in CAA patients. "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," Bruce emphasized. This approach could help mitigate the substantial dementia risk identified, potentially improving long-term outcomes for affected individuals.
However, the research has limitations. It relied on administrative diagnosis codes from Medicare claims, which are an "imperfect proxy for clinical diagnoses," according to Bruce. The study also lacked imaging data to rigorously confirm CAA and stroke diagnoses. As an abstract presented at a scientific meeting, the findings are considered preliminary until published in a peer-reviewed journal. Further prospective studies with standardized diagnostic approaches are needed to validate these results and explore the underlying mechanisms linking CAA to dementia.
