A new blood test that detects a protein linked to Alzheimer's disease could predict cognitive decline in older adults up to a decade before symptoms appear, according to Harvard-led research presented at the Alzheimer's Association International Conference in London. The test measures levels of P-tau217, a tau protein biomarker associated with Alzheimer's, and researchers say elevated readings correlate with a greater likelihood of future dementia. The findings could offer a significant step towards earlier diagnosis, allowing patients and doctors more time to plan care and potentially intervene before serious cognitive symptoms set in.

Dr Jeremy Koppel, co-director of the Litwin-Zucker Center, said the test's ability to flag risk five to ten years in advance could reshape how clinicians understand and track the progression of Alzheimer's. Because the test relies on a simple blood draw rather than more invasive or costly procedures such as brain scans or spinal taps, it could make early risk assessment far more accessible to older adults, even before any noticeable memory or thinking problems develop.