It shows signs of the disease may be in the brain nearly a decade before symptoms begin.
Magnetic resonance imaging revealed shrinkage in brain areas which have been previously associated with the disease.
A recent study published in the journal Neurology focused on adults age 65 and older. It found that brain scans showed key brain areas were likely to be smaller in the people developed Alzheimer's nearly 10 years later.
There are about 5 million people with the disease in the U.S.