SC Alzheimer's Disease Alzheimer's Disease Chapter 24. Chronic Illnesses Alzheimer's disease afflicts nearly 4 million Americans. It strikes over 45 percent of the population over age 85 and about 10 percent of those over age 65. In rare instances, Alzheimer's comes earlier than age 65. 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 8 years from the time symptoms start.