Stanford Center for Memory Disorders

What is Alzheimer's Disease

Alzheimer's disease is a progressive, neurodegenerative disease that occurs when nerve cells in the brain die and often results in the following:

With Alzheimer's disease, motor function is often preserved.

When Alzheimer's was first identified by German physician, Alois Alzheimer, in 1906, it was considered a rare disorder. Today Alzheimer's disease is recognized as the most common cause of dementia (a disorder in which mental functions deteriorate and break down). An estimated 5.3 million Americans have Alzheimer's disease. According to the Alzheimer's Association, this number includes 5.1 million people over the age of 65, as well as 200,000 to 500,000 people younger than 65 who have early-onset Alzheimer's and other types of dementias.

Alzheimer's Disease
Alzheimer's Disease (Click image to enlarge)

How is Alzheimer's different from other forms of dementia?

Alzheimer's disease is distinguished from other forms of dementia by characteristic changes in the brain that are visible only upon microscopic examination during autopsy. Brains affected by Alzheimer's disease often show presence of the following:

Another characteristic of Alzheimer's disease is the reduced production of certain brain chemicals necessary for communication between nerve cells, especially acetylcholine, as well as norepinephrine, serotonin, and somatostatin.

What causes Alzheimer's disease?

Although intense investigation has been underway for many years, the causes of Alzheimer's disease are not entirely known. Suspected causes often include the following:

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