TL;DR
Get health and wellness essentials delivered free with Prime
- Fast, free delivery on millions of items
- Prime Video, Amazon Music and more included
- Member-only deals all year
A study pooling data from 2,684 older adults without cognitive impairment found that very high levels of the blood marker p-tau217 were associated with an estimated 38% risk of cognitive impairment within five years and 78% within 10 years. The 10-year estimate is less certain because it relies on substantially fewer observations, and researchers do not recommend these tests for routine screening of people without symptoms.
Researchers analyzing data from 2,684 older adults found that very high blood levels of the Alzheimer’s-associated marker p-tau217 were linked to an estimated 38% chance of cognitive impairment within five years and 78% within 10 years. The findings, presented at the Alzheimer’s Association International Conference and published in JAMA, suggest the marker could help estimate risk before symptoms appear, but the researchers say blood tests are not currently recommended for routine screening of people without symptoms.
The study combined information from six observational studies and clinical trials in North America, Japan and Australia. Participants had no signs of cognitive impairment when they entered the research. Researchers analyzed blood samples for p-tau217, a protein marker associated with Alzheimer’s disease, and used PET brain scans to measure baseline brain changes. Annual assessments tracked memory, thinking and other cognitive abilities.
Study data stretched from participants who enrolled as early as 2004 to follow-up assessments conducted in 2025. About 478 participants developed cognitive impairment. Among those with very high p-tau217 levels, researchers estimated a 38% probability of impairment within five years and 78% within 10 years. The longer-term estimate drew on substantially less data, so it is more uncertain than the five-year estimate.
The association between p-tau217 and later impairment remained after researchers accounted for amyloid-beta plaques detected by PET scans and genetic risk factors such as APOE4. The study therefore suggests the blood marker may add information to those measures; it does not establish that a test can predict with certainty whether a particular person will develop symptoms.
Potential for Earlier Risk Estimates
The findings address a practical question about Alzheimer’s testing: whether a blood marker can say something about the likelihood of future cognitive problems, not just indicate biological changes associated with the disease. A blood test could be easier to administer than brain imaging and might eventually help clinicians identify people who could be eligible for prevention studies or treatments, if those become available for people at elevated risk.
For now, the results do not support using the test to screen people who have no symptoms. A risk estimate is not a diagnosis, and the study does not show that testing healthy people improves their health outcomes. The researchers say there are not yet established disease-modifying treatments for otherwise healthy people identified as being at high risk. That gap matters: knowing a risk estimate may have limited practical value when no proven intervention is available for that group.
Products Worth Considering
Fitbit Sense 2 Advanced Health and Fitness Smartwatch, Blue Mist/Pale Gold
Levoit Core 400S-P Smart Air Purifier for Large Rooms
Levoit Core 600S-P Smart Air Purifier for Large Rooms
As an affiliate, we earn on qualifying purchases.
How the Six-Study Analysis Worked
A blood test measuring p-tau217 recently received federal clearance, prompting interest in how blood-based measures might contribute to Alzheimer’s assessment. The study reported here focused on a different but related question: whether the marker, measured in people with normal cognitive function, was associated with impairment years later.
By combining six cohorts, the researchers could examine outcomes across a longer period and a larger group than a single study might provide. Participants’ blood results were compared with later cognitive assessments, while PET scans and genetic information helped researchers evaluate whether p-tau217 added predictive information beyond other known measures. The analysis was observational: it found associations between initial biomarker levels and later outcomes, rather than showing that the marker itself causes cognitive decline.
“This is a critical step toward better understanding what p-tau217 can tell us about a person’s risk for cognitive impairment.”
— Rachel F. Buckley, lead author and cognitive neuroscientist at the Mass General Brigham Neuroscience Institute
Limits of the Risk Estimates
The 78% estimate applies to participants with very high p-tau217 levels in this study; it is not a guaranteed outcome for an individual or a general estimate for everyone who takes a blood test. Researchers had substantially fewer observations at 10 years, which makes the long-range estimate less certain. The source report does not provide the detailed confidence intervals or a full breakdown of how estimates varied across participants.
The researchers also cautioned that people enrolled in the six studies may not represent the broader population. The results show an association and added predictive information after accounting for PET-detected amyloid and genetic risk factors, but further work is needed to establish how well the estimates apply across different groups and clinical settings. It is also unclear whether acting on a high-risk result would improve outcomes for people who currently have no symptoms.
What Could Change Clinical Use
Researchers say the immediate issue is whether ongoing trials of disease-modifying therapies show benefits for people identified before symptoms develop. If effective treatments become available for this group, p-tau217 testing could be studied as a way to help select participants or guide care. Until then, the study authors do not recommend currently available Alzheimer’s blood tests for asymptomatic people.
Further research will also need to test risk estimates in broader, more representative populations and clarify how results should be interpreted over different time horizons. The study does not set a date for any change in screening guidance. For people considering testing or concerned about memory changes, decisions should be discussed with a qualified health professional.
Key Questions
What does the p-tau217 blood test measure?
It measures phosphorylated tau 217, a blood biomarker associated with Alzheimer’s disease. In this study, researchers examined whether its level in people without cognitive impairment was associated with later cognitive problems.Does a high result mean someone will develop Alzheimer’s?
No. The study reports estimated probabilities among participants with very high marker levels, not certainty for an individual. The reported outcome was cognitive impairment; a test result alone is not a diagnosis.How reliable is the 10-year estimate?
The researchers estimated a 78% probability of cognitive impairment within 10 years for participants with very high p-tau217 levels. They cautioned that the estimate is less certain because substantially fewer observations were available over that period.Should people without symptoms get tested?
The study authors say currently available blood tests are not recommended for routine screening of asymptomatic people. They cite the lack of established disease-modifying treatments for otherwise healthy people found to be at elevated risk.What would make the test more useful in the future?
The authors say testing could help identify people who might benefit from preventive treatments if ongoing trials show those treatments work for people at elevated risk before symptoms. That possibility has not yet been established.Source: sciencedaily.com
