Pathways Contact PEIA Home Return to Index Alzheimer's Disease Alzheimer's disease afflicts nearly four million Americans, about 10 percent of the population over age 65, and over 45 percent of those over age of 85. No one knows what causes Alzheimer's disease.
Some research hints that a virus or infectious agent is the culprit.
Two brain chemicals are known to be produced less in Alzheimer's disease. Signs and Symptoms Alzheimer's disease has a gradual onset. The signs and symptoms may progress in stages. How quickly they occur varies from person to person. The course of the disease averages eight years from the time symptoms start.