A simple blood test measuring the biomarker p-tau217 can estimate an older adult’s risk of developing cognitive impairment up to five years before symptoms appear, according to a recent study involving approximately 2,700 cognitively unimpaired participants. While currently used in specialty care for patients already showing symptoms, these findings suggest a potential future role for blood-based screening in healthy populations.
Predicting Cognitive Risk Through Blood Biomarkers
The study, which tracked participants across North America, Japan, and Australia, utilized p-tau217 blood tests to track protein buildups associated with Alzheimer’s disease. Researchers found that higher levels of this protein consistently correlated with an increased risk of cognitive decline over a five-year period. Participants with “very high” levels of p-tau217 faced a 38 percent risk of developing cognitive impairment within five years, compared to just 12 percent for those with low levels.
Rachel Buckley, PhD, an associate professor of neurology at Harvard Medical School and the study’s first author, notes that these results provide meaningful information regarding future risk for those currently showing no signs of memory issues. The research was recently highlighted for its contribution to the field of precision medicine in Alzheimer’s care.
Did you know? While the study looked at a 10-year risk estimate—reaching 78 percent for the highest p-tau217 group—researchers caution that these long-term figures are less certain because only 5 percent of the study participants were followed for that duration.
The Shift Toward Early Intervention
Current guidance from the Alzheimer’s Association limits the use of these blood tests to diagnostic workups for patients already experiencing cognitive symptoms. Kaitlin Seibert, MD, a behavioral neurologist at Cleveland Clinic’s Center for Brain Health, explains that this research represents a shift toward identifying the disease earlier, which is critical for future prevention trials.
For researchers, these tests offer a more practical alternative to traditional methods. Historically, confirming Alzheimer’s-related changes required spinal fluid tests or brain scans. A blood test could theoretically allow for larger, more efficient clinical trials by identifying candidates who are statistically more likely to develop symptoms during the study period.
Barriers to Routine Screening
Despite the promise of the data, medical experts emphasize that these tests are not yet ready for routine screening in healthy adults. A primary concern is the lack of a clear medical action for a cognitively healthy person who receives a high-risk result. According to Dr. Seibert, there is currently insufficient evidence that widespread screening improves health or changes what is recommended for most people.
Clinical implementation also faces significant hurdles. Doctors must still determine how external factors—such as kidney disease or other brain conditions—might influence biomarker levels. Furthermore, the “cutoffs” used in this research to define high and low risk are not yet standardized for everyday clinical practice. Researchers also observed that men in the study appeared more likely to develop cognitive impairment than women, a trend that requires further investigation to understand biological differences.
Frequently Asked Questions
Is the p-tau217 blood test available for healthy people today?
No. Current medical guidance suggests these tests should only be used in specialized care settings for patients who are already exhibiting symptoms of memory or thinking problems.
Why can’t doctors just use these tests for everyone?
There is currently no clear medical action for a healthy person who tests positive for these biomarkers. Because the long-term clinical impact of such screening is unknown, it is not yet recommended for routine check-ups.
How does this test differ from a brain scan?
PET scans are used for measuring amyloid, but they are expensive. Blood tests like p-tau217 are a more practical way to identify people for research than relying solely on brain scans or spinal fluid tests.
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