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Alzheimer's Disease

An irreversible, progressive condition in which nerve cells in the brain degenerate, and the size of the brain decreases.

Alzheimer's disease is the most common degenerative brain disorder, although onset of the disease is rare before the age of 60. After that age, the incidence of Alzheimer's disease increases steadily, and more than one-quarter of all individuals above the age of 85 have this disease. In addition, Alzheimer's disease is the cause of about three-quarters of all cases of dementia in individuals above the age of 65. General interest and research focusing on the cause and treatment of this condition have grown in recent years because the number of elderly persons in the population is increasing.

The cause of Alzheimer's disease is not known, but several theories of causality have been advanced. These theories propose genetic, environmental, viral, immunological, biochemical, and other causes for the disease. The specific features of Alzheimer's disease vary from individual to individual, but the general course of the disease is fairly consistent in most cases. The symptoms of the disease tend to be more severe at night. The first stage of Alzheimer's disease is usually forgetfulness, accompanied by some anxiety and mild depression. This usually develops into a more serious loss of memory, especially of recent events, moderate spatial and temporal disorientation, loss of ability to concentrate, aphasia, and increased anxiety. This set of symptoms is usually followed by profound spatial and temporal disorientation, delusions, hallucinations, incontinence, general physical decline, and death.

See also Dementia

Brain tissue damaged by Alzheimer's disease. (Photo by Cecil Fox/Science Source. National Audubon Society Collection/Photo Researchers, Inc. Reproduced by permission.)

Further Reading

Edwards, Allen. When Memory Fails. New York: Plenum, 1994.

Gregg, Daphna. Alzheimer's Disease. Boston: Harvard Medical School Health Publications, 1994.

Additional topics

Psychology EncyclopediaDiseases, Disorders & Mental Conditions