Doctors have long wanted a simple blood test that could tell whether someone is likely to develop Alzheimer’s disease before memory loss begins.
Today, diagnosing the disease often requires brain scans or spinal fluid tests, which can be expensive or invasive.
A reliable blood test could make early detection much easier and allow researchers to identify people years before symptoms appear.
Researchers from the Mass General Brigham Neuroscience Institute and international partners have taken an important step toward that goal by studying a blood marker called p-tau217.
This marker reflects abnormal changes in tau, a protein that becomes damaged in Alzheimer’s disease and contributes to the destruction of brain cells.
The research was presented at the Alzheimer’s Association International Conference and published in JAMA.
Scientists analysed data from six separate studies involving 2,684 older adults from Australia, Japan, and North America who had normal memory and thinking abilities when they entered the research.
Each participant had a blood sample collected to measure p-tau217 levels and underwent PET imaging to examine changes inside the brain. Researchers then monitored their memory and thinking every year. Across the entire study, 478 people eventually developed cognitive impairment.
The results showed a clear pattern. Participants with the highest p-tau217 levels faced a much greater chance of developing cognitive problems than those with lower levels. Their estimated risk was 38 percent over the next five years and 78 percent after ten years. Although the ten-year estimate is encouraging, the researchers note that fewer participants had reached that length of follow-up, making those figures less certain.
One of the most important discoveries was that the blood marker remained informative even after accounting for other major Alzheimer’s risk factors, including amyloid deposits in the brain and inherited genetic risk. This means the test may provide unique information rather than simply repeating what existing tests already show.
Despite these promising findings, researchers caution against widespread testing of healthy adults. According to senior author Dr. Reisa Sperling, knowing someone has a high-risk result does not yet change medical advice very much because there are still limited proven treatments for people who have no symptoms. Healthy habits such as regular exercise, nutritious eating, good sleep, and management of blood pressure and diabetes remain the best evidence-based ways to support brain health.
Researchers believe the value of the test could increase dramatically if current prevention trials succeed. In the future, doctors might use p-tau217 testing to identify people who could receive new medicines before permanent brain damage occurs.
Like all studies, this research has limitations. Participants were volunteers in research projects and may not fully represent the wider community. Longer studies will also be needed to understand risk over decades instead of several years.
Overall, the findings move Alzheimer’s research closer to a future where doctors can estimate a person’s risk using a simple blood sample instead of more complicated procedures. While routine screening is still some distance away, this work provides a strong scientific foundation for future preventive care.
If you care about Alzheimer’s, please read studies about the likely cause of Alzheimer’s disease , and new non-drug treatment that could help prevent Alzheimer’s.
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