Blood test predicts Alzheimer’s decline a decade early

A simple blood test for a protein linked to Alzheimer's disease can predict cognitive decline up to a decade before symptoms appear, according to a major international study presented this week. The findings, which show the test can identify high-risk individuals while they are still cognitively healthy, mark a significant advance toward earlier detection and potential prevention of dementia.

The research, led by scientists at the Mass General Brigham Neuroscience Institute, was presented on Wednesday, July 15, 2026, at the Alzheimer's Association International Conference in London and simultaneously published in the Journal of the American Medical Association. The study analyzed data from nearly 2,700 older adults with normal thinking and memory across six studies in North America, Australia, and Japan. Participants provided blood samples and underwent PET brain scans at the outset and were followed with annual cognitive assessments for years, with some tracked since 2004.

The study focused on levels of a protein in the blood called phosphorylated tau 217 (ptau217), a biomarker for Alzheimer's-related brain changes. Researchers found that cognitively healthy individuals with...