A common but often hidden brain condition could make older adults four times more likely to develop dementia.
This condition is called cerebral amyloid angiopathy, or CAA. It happens when a protein called amyloid builds up in the blood vessels of the brain, making them weak and more likely to bleed.
While small amounts of this protein can appear with age and not cause harm, CAA occurs when the buildup becomes serious enough to damage the brain’s blood vessels and affect thinking.
In a new study presented at the American Stroke Association’s International Stroke Conference 2026 in New Orleans, researchers found that people with CAA are at much higher risk of developing dementia within five years, whether or not they have had a stroke.
This suggests that CAA itself—not just the strokes it can cause—is a key factor in increasing dementia risk.
CAA can lead to two types of strokes: bleeding strokes (hemorrhagic) and clot-related strokes (ischemic).
In severe cases, amyloid protein can weaken vessel walls so much that they crack and leak blood into the brain, causing further damage. CAA is also common in people with Alzheimer’s disease and may contribute to memory loss and confusion.
The study was led by Dr. Samuel S. Bruce, a neurology professor at Weill Cornell Medicine in New York City.
His team looked at data from over 1.9 million older adults, all aged 65 or older, using Medicare records from 2016 to 2022. They tracked people over time to see who developed dementia, and whether having CAA or a stroke—or both—increased that risk.
They discovered that people with CAA had a much higher chance of being diagnosed with dementia than those without it. The risk remained high whether or not the person also had a stroke.
Here’s what they found: 42% of people with CAA were diagnosed with dementia within five years, compared to only 10% of people without CAA. People who had both CAA and a stroke were 4.5 times more likely to develop dementia at any point in time than people with neither condition.
Those with CAA but no stroke were still 4.3 times more likely. Even stroke alone increased the risk 2.4 times, but that was much lower than the risk seen with CAA.
What surprised researchers was that CAA patients without stroke had nearly the same risk of dementia as those with stroke. This means that other brain changes caused by CAA—besides strokes—may be playing a big role in memory loss.
As Dr. Bruce explained, “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.”
Dr. Steven Greenberg, a professor at Harvard Medical School and expert in stroke research, added, “Diseases of the brain’s small blood vessels are major contributors to dementia. This is especially true for CAA, which often occurs with Alzheimer’s, making for a dangerous combination.”
However, this study had some limits. It used Medicare insurance data, which relies on diagnostic codes from hospital and clinic records. These codes might not always be completely accurate. Also, the researchers didn’t have access to brain scans to double-check the CAA and stroke diagnoses.
Still, this study offers an important warning. Even without a stroke, CAA can put people at high risk for dementia. More research is needed, especially studies that follow patients forward in time and use better methods to confirm diagnosis.
For now, doctors and families should pay close attention when someone is diagnosed with CAA—and not wait for a stroke to act.
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