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Health A-Z

Medical Content Created by the Faculty of the
Harvard Medical School

Alzheimer's Disease

What Is It?

Alzheimer's disease damages the brain's intellectual functions (memory, orientation, calculation), but at first, it largely spares those parts of the brain that control sensation and movement. Short term memory often is affected early. Gradually other intellectual functions deteriorate and judgment becomes impaired. In later stages of the disease, most people with advanced Alzheimer's lose their ability to do normal daily activities. Alzheimer's usually begins later in life, generally after age 60. Occasionally, it will affect younger people.

Although scientists are uncertain about what specifically causes the symptoms of Alzheimer's disease, those that are affected consistently develop excessive deposits of proteins called amyloid and TAU. It is believed that these proteins distort communication between brain cells. Also, levels of a chemical called acetylcholine that helps transmit messages between brain cells begins to drop, adding to the communication problems. Eventually, brain cells themselves are affected. They begin to shrivel and die, causing certain areas of the brain to shrink.

Alzheimer's disease is the most common cause of dementia, accounting for nearly 70% of all cases in people aged 65 and older. More than 5 million people in the United States currently have the disease.

Everyone is born with the potential to develop Alzheimer's disease. Your lifetime risk of developing the disease is about 10% to 15%. However, several factors may increase your risk:

• Age — The older you get, the greater your chance of developing Alzheimer's disease.

• Family history — If members of your family, especially parents or siblings, have Alzheimer's or have died of it, your risk of developing the disease increases. Your personal risk also depends on several factors, including how many family members are affected with Alzheimer's.

• Genetic factors — Inheriting certain genes increases your lifetime risk of getting Alzheimer's disease.

From Health A-Z, Harvard Health Publications. Copyright 2007 by the President and Fellows of Harvard College. All rights reserved. Written permission is required to reproduce, in any manner, in whole or in part, the material contained herein. To make a reprint request, contact Harvard Health Publications. Used with permission of StayWell.

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