p-tau217 blood test flags 38% five-year Alzheimer’s impairment risk

Mass General Brigham researchers reported Oct. 30 in a ScienceDaily research-organization release that high blood p-tau217, a tau protein marker, marked a 38% five-year cognitive-impairment risk in cognitively normal older adults.

The JAMA study matters because it tests whether a blood biomarker can estimate risk before symptoms appear. Among the highest-risk group, the estimated 10-year risk reached 78%, though that longer estimate used much less data.

Researchers combined data from six observational studies and clinical trials in North America, Japan and Australia. The analysis included 2,684 older adults who had no cognitive impairment when they entered the studies.

Participants gave blood samples at enrollment, received positron emission tomography scans, a brain-imaging method, and had annual checks of memory and thinking. Some participants entered the research in 2004, and the latest follow-up assessments occurred in 2025.

About 478 participants later developed cognitive impairment. Higher p-tau217 levels at the start were strongly associated with later impairment, according to the ScienceDaily account of the JAMA paper.

"This is a critical step toward better understanding what p-tau217 can tell us about a person's risk for cognitive impairment," said Rachel F. Buckley, lead author and cognitive neuroscientist with the Mass General Brigham Neuroscience Institute.

The biomarker added information beyond amyloid-beta plaques, abnormal protein deposits visible on PET imaging, and beyond genetic risk factors such as APOE4. A blood test measuring p-tau217 has recently received federal clearance, according to the source.

The study does not support routine Alzheimer’s risk screening for people without symptoms. "We do not yet have disease-modifying treatments for people who find out they are at high risk for developing cognitive impairment due to Alzheimer's disease, which is why we don't recommend currently available blood tests for asymptomatic individuals," said Reisa Sperling, senior and corresponding author.

The study cannot show whether testing healthy older adults improves outcomes. The source said participants may not represent the broader population, and the analysis estimated risk over limited periods rather than lifetime risk.

The findings apply to older adults who were cognitively normal at enrollment, not to younger adults or people already diagnosed with cognitive impairment. The ScienceDaily account did not provide sex breakdowns or confidence intervals for the risk estimates.

Funding included the National Institutes of Health, the U.S. Department of Defense, Eli Lilly, the Alzheimer’s Association, the GHR Foundation, an anonymous foundation and private donors. Buckley reported NIH grants outside the submitted work, and Sperling reported grants, industry consulting and clinical-trial funding outside the work.

For now, the practical role is research triage. Sperling said p-tau217 can help find people at high risk for future Alzheimer’s dementia who may qualify for prevention trials.

Source: research-organization release, ScienceDaily Health, Oct. 30, 2026.

Atlas360 reports health research and does not provide medical advice.