A blood test that measures a protein linked to Alzheimer's disease can predict whether cognitively healthy older adults will develop memory problems or dementia up to a decade before symptoms appear, according to new research published in JAMA on July 14, 2026, and simultaneously presented at the Alzheimer's Association International Conference (AAIC) in London on July 15. The finding, described by researchers as establishing the "prognostic value" of the p-tau217 blood biomarker, moves the test beyond diagnosis into the realm of long-range prediction for people who feel completely normal today.
In the study, adults with very high levels of p-tau217 in their blood had an approximately 78% risk of developing cognitive impairment over 10 years, and about a one-in-three chance within five years, even though they showed no symptoms of cognitive decline when their blood was drawn.
