Alzheimer's disease (pronounced AHLZ-hi-merz ) is a disorder that destroys cells in the brain.

The disease is the leading cause of dementia, a condition that involves gradual memory loss, decline in the ability to perform routine tasks, disorientation, difficulty in learning, loss of language skills, impairment of judgment, and personality changes.

As the disease progresses, people with Alzheimer's become unable to care for themselves. The loss of brain cells eventually leads to the failure of other systems in the body. The rate of progression of Alzheimer's varies from person to person. The time from the onset of symptoms until death ranges from 3 to 20 years. The average duration is about 8 years.

One in 10 people over the age of 65 and nearly half of those over 85 years has Alzheimer's disease, The disorder is the third-most expensive illness in the United States, behind only heart disease and cancer.