Causes

Studies show that chemical and structural changes occur in the brains of people with Alzheimer's disease. These changes interfere with a person's ability to process, store, and retrieve information. It is not known why these changes occur.

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Scientists have found two significant abnormalities in the brains of people with Alzheimer's disease: twisted nerve cell fibers, known as neurofibrillary tangles, and a sticky protein called beta amyloid, which forms structures called plaques. Plaques and tangles are associated with damage to healthy brain cells, causing the brain to atrophy and shrink.

Another characteristic of Alzheimer's disease is the reduced production of certain chemicals in the brain that are necessary for communication between nerve cells. These chemicals, called neurotransmitters, include acetylcholine, serotonin, and norepinephrine.

In the area of the brain responsible for memory, the hippocampus, there is a loss of nerve cells, and decreases occur in the levels of chemicals needed for carrying messages back and forth between the nerve cells.