A new tool has been developed to predict the risk of dementia, including Alzheimer's disease, years before symptoms appear. The tool may involve a blood test, and some reports suggest it can forecast the onset of dementia up to 25 years in advance, although it is unclear if this applies to all individuals or just specific groups, such as women. The development of the tool is attributed to scientists at the Mayo Clinic, with research also involving health record data and machine learning.