Alzheimer’s disease is the most common cause of dementia, affecting millions of older adults worldwide.
The disease slowly damages brain cells, causing memory loss, confusion, and problems with thinking and daily activities. Scientists know that changes in the brain begin many years before the first symptoms appear.
Because of this, researchers have been searching for simple ways to identify people who are at high risk long before memory problems develop.
One promising approach is a blood test that measures a protein called phosphorylated tau 217, or p-tau217. Tau proteins are naturally found in the brain, but in Alzheimer’s disease they become abnormal and form tangles that damage brain cells.
Recently, a blood test measuring p-tau217 received clearance from U.S. regulators, raising hopes that it could become a useful tool for detecting Alzheimer’s-related changes without the need for expensive brain scans.
A new international study led by researchers at the Mass General Brigham Neuroscience Institute has now examined how well this blood test predicts future memory problems in people who are still cognitively healthy.
The findings were presented at the Alzheimer’s Association International Conference and published at the same time in JAMA.
Researchers combined information from six studies conducted in North America, Australia, and Japan. In total, 2,684 older adults with normal thinking and memory were included. At the beginning of each study, participants gave blood samples for p-tau217 testing and also underwent PET brain scans.
They then completed yearly memory and thinking assessments. Some participants had been followed since 2004, with the latest follow-up extending into 2025.
During the study, 478 participants developed cognitive impairment. The researchers found that people with very high p-tau217 levels had a much greater chance of experiencing memory and thinking problems. Their absolute risk reached 38 percent within five years and increased to 78 percent over ten years, although the longer-term estimate was based on fewer participants and should be interpreted with caution.
Importantly, the blood test predicted future risk even after researchers considered other important risk factors such as amyloid plaques detected by PET scans and inherited genetic risk, including the APOE4 gene. This suggests that p-tau217 may provide additional information beyond existing tests.
Even with these encouraging findings, the researchers stress that the blood test is not yet recommended for healthy people with no symptoms. At present there are still limited disease-modifying treatments that can be offered solely because someone has a high-risk blood test. Senior author Dr. Reisa Sperling explained that the advice remains the same regardless of the result: stay physically active, eat a healthy diet, sleep well, and look after overall health.
The situation could change in the future if ongoing prevention trials prove successful. If new treatments can delay Alzheimer’s before symptoms appear, blood tests like p-tau217 may help identify people most likely to benefit from early treatment and closer monitoring.
The study has some limitations. Most participants came from research studies rather than the general population, which means the results may not apply equally to everyone. The researchers also need longer follow-up to better estimate lifetime risk instead of only five- and ten-year risk.
Overall, this study is an important step toward more personalized Alzheimer’s prediction. It shows that a simple blood test may one day help doctors estimate an individual’s future risk, much like cholesterol testing helps estimate the risk of heart disease.
However, more research is needed before the test becomes part of routine screening for healthy adults.
If you care about Alzheimer’s disease, please read studies about the protective power of dietary antioxidants against Alzheimer’s, and eating habits linked to higher Alzheimer’s risk.
For more health information, please see recent studies that oral cannabis extract may help reduce Alzheimer’s symptoms, and Vitamin E may help prevent Parkinson’s disease.
Source: Mass General Brigham.
