Blood test measuring p-tau217 may forecast Alzheimer’s decline up to ten years ahead

Researchers from Harvard Medical School presented data at the Alzheimer’s Association International Conference in London showing that a blood test for the protein p-tau217 can identify older adults at elevated risk of future cognitive decline. The study, published in the Journal of the American Medical Association, followed nearly 2,700 participants with normal cognition, averaging 70 years old, for up to a decade. Individuals with the highest p-tau217 concentrations had an estimated 78% probability of developing cognitive impairment within ten years and about a one-in-three chance within five years, while those with moderate elevations faced a 45% ten-year risk. The biomarker reflects the accumulation of tau protein, which forms neurofibrillary tangles linked to memory loss, and provided risk information beyond that obtained from brain imaging or genetic testing.

"Once verified, these blood tests could be used to recruit patients for clinical trials of treatments to prevent cognitive decline and dementia," said Rachel Buckley, lead author and associate professor of neurology at Harvard Medical School.

"In the future, when treatments are approved for use early in the disease process, these tests could help guide monitoring, treatment decisions and counseling for patients and families," Buckley added.

The researchers cautioned that p-tau217 alone does not determine an individual’s outcome; factors such as age, genetics, kidney function and racial background also affect biomarker levels and dementia risk. They called for longer studies involving more diverse populations to refine risk estimates.

Maria Carrillo, chief science officer at the Alzheimer’s Association, said early identification of at-risk individuals could change how the disease is diagnosed and treated, potentially allowing interventions before symptoms appear.