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Health A-Z

Medical Content Created by the Faculty of the
Harvard Medical School

What Is It?

Alzheimer's disease (AD) is a loss of brain functions that worsens over time. It is a form of dementia.

Alzheimer's disease damages the brain's intellectual functions. Short term memory often is affected early. Gradually other intellectual functions deteriorate. Judgment becomes impaired. Most people with advanced AD lose their ability to do normal daily activities.

Alzheimer's usually begins after age 60. Occasionally, it affects younger people.

Scientists are uncertain about what causes the symptoms of AD. Alzheimer's patients develop excessive deposits of two proteins in their brains. Researchers believe that these proteins distort communication between brain cells.

A chemical called acetylcholine may also be involved. It helps transmit messages between brain cells. Levels of acetylcholine begin to drop in patients with AD. This may add to the communication problems between brain cells.

Eventually, brain cells themselves are affected. They begin to shrivel and die.

The following factors may increase your risk of Alzheimer's disease:

  • Age. Risk increases with age.

  • Family history. If members of your family, especially parents or siblings, have or had AD, your risk increases.

  • Genetic factors. Inheriting certain genes increases your risk.

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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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