July 1, 2026

Alzheimer’s proteins in blood linked to midlife cognition

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Researchers found high blood levels of Alzheimer’s proteins among people in their 50s and 60s with memory decline.

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The brain changes that underlie Alzheimer’s disease begin decades before thinking and memory are affected. The two hallmarks of Alzheimer’s in the brain are tangles of the protein tau and plaques made of amyloid-beta, a protein that is naturally produced in the brain. Brain scans and spinal fluid tests can detect these proteins, but the tests are either expensive or highly invasive. 

Blood tests that measure amyloid-beta and tau are cheaper and easier to perform. However, most studies of such tests have been in older adults and among people who have already been diagnosed with Alzheimer’s. 

A team of NIH-funded researchers, led by Dr. Kristine Yaffe of the University of California, San Francisco, examined how blood levels of amyloid-beta and tau related to cognitive function in people in their 50s and 60s. The team’s results were published on May 30, 2026, in Lancet. 

The researchers used data from the long-running NIH-funded Coronary Artery Risk Development in Young Adults (CARDIA) study. They analyzed blood samples from 1,350 CARDIA participants at a follow-up exam between 2020 and 2022. The participants also completed cognitive tests at the exam. None of them had been diagnosed with any form of dementia. 

The team measured the levels of three biological markers, or biomarkers, in CARDIA participants’ blood. These biomarkers—certain forms of amyloid-beta and tau proteins in blood—are known to indicate the presence of amyloid-beta plaques and tau tangles in the brain. Between 4% and 15% of participants had biomarker levels in their blood that were high enough to suggest they had Alzheimer’s hallmarks in their brains. 

These participants with high levels of Alzheimer’s blood biomarkers did worse on tests of processing speed, which gauge how quickly the brain receives and interprets new information. They also had worse executive function, which is the ability to manage thoughts, behavior, and emotions to complete tasks and achieve goals. 

Most of the participants had also undergone cognitive tests at their CARDIA exam five years earlier. On average, cognitive abilities worsened only modestly over the five years between the exams. But participants with high levels of Alzheimer’s biomarkers were much more likely to show a large decrease in processing speed. They also showed steeper declines in verbal memory, which is the ability to store and recall words in long-term memory, a key aspect of Alzheimer’s. 

The results suggest blood tests that measure amyloid-beta and tau proteins might help to identify early brain changes related to Alzheimer’s disease. More research is needed to determine what high levels of these proteins in the blood mean over time. But the results could one day allow early treatments and lifestyle changes aimed at delaying symptoms.  

“Detecting the disease early means patients can target modifiable risk factors and maybe seek other care,” Yaffe says. 

—by Brandon Levy 

Related Links

• Blood test predicts start of Alzheimer’s disease symptoms
• Accurate blood test for Alzheimer’s disease
• Blood test for early Alzheimer's detection
• Beyond basic blood tests
• Alzheimer’s and dementia
• Coronary Artery Risk Development in Young Adults Study (CARDIA)
• About Alzheimer’s (CDC)
• FDA clears first blood test used in diagnosing Alzheimer’s disease

References

Alzheimer's disease neuropathology plasma biomarkers and cognition in midlife: a community-based cohort study. Jiang X, Hoang TD, Shaw LM, Jacobs DR Jr, Nasrallah IM, Bryan RN, Yaffe K. Lancet. 2026 May 30;407(10544):2208-2216. doi: 10.1016/S0140-6736(26)00515-5. PMID: 42208562.

Funding

NIH’s National Institute on Aging (NIA) and National Heart, Lung, and Blood Institute (NHLBI); Alzheimer’s Association.