Blood test measuring p-tau217 may forecast Alzheimer's risk years ahead

A blood test that detects the protein p-tau217 could identify older adults who are likely to develop Alzheimer’s-related cognitive impairment over the next five to ten years, researchers reported. The findings, published in JAMA and presented at the Alzheimer’s Association International Conference in London, were based on data from 2,684 participants who were symptom-free at enrollment and received annual cognitive assessments.

Participants with the highest p-tau217 levels faced a 38% risk of impairment within five years, rising to 78% by ten years, while those with very low levels had a correspondingly low risk. The test, already used to aid diagnosis in symptomatic individuals, measures a form of tau that reflects amyloid plaque burden and may indicate the onset of tau tangles.

“Wait and get tested when you can potentially do something about it,” said Dr. Reisa Sperling, senior author and senior researcher at the Mass General Brigham Neuroscience Institute. “I’d still tell them to eat well, sleep well, exercise a lot and stay engaged.”

Experts cautioned that the long-term risk estimates are based on a limited number of participants followed for a full decade and that other health conditions could influence outcomes. Dr. Suzanne Schindler and Dr. David Wolk, who commented on the study, noted that the biomarker is not yet precise enough for individualized prognosis but represents an important advance in understanding disease progression.

Clinicians also warned against premature use of the test by individuals with a family history of Alzheimer’s, emphasizing that its utility will depend on the development of effective preventive therapies.