Blood test could predict when Alzheimer's symptoms will start years in advance

A simple blood test could predict not only a person’s risk of developing Alzheimer’s disease, but also the year symptoms will begin.

Researchers at the Washington University School of Medicine in St. Louis set out to determine if levels of a specific protein in the blood could be used as a "biological clock" to predict when signs of the disease will emerge.

The specific protein, known as p-tau217, forms "tangles" in the brain that disrupt communication between nerve cells. In a healthy brain...