Causes

Scientists do not know what causes Alzheimer’s disease. It may be a combination of various genetic and environmental factors that trigger the process in which brain nerve cells are destroyed.

Genetic Factors

Genetics certainly plays a role in early-onset Alzheimer's, a rare form of the disease that usually runs in families. Scientists are also investigating genetic targets for late-onset Alzheimer's, which is the more common form. At this time, only one gene, apolipoprotein E (ApoE) has been definitively linked to late-onset Alzheimer's disease. However, only a small percentage of people carry the form of ApoE that increases the risk of late-onset Alzheimer's. Other genes or combinations of genes may be involved.

Environmental Factors

Researchers have investigated various environmental factors that may play a role in Alzheimer’s disease or that trigger the disease process in people who have a genetic susceptibility. Some studies have suggested an association between serious head injuries in early adulthood and Alzheimer’s development. Lower educational level, which may decrease mental and activity and neuron stimulation, has also been investigated. To date, there does not appear to be any evidence that infections, metals, or industrial toxins cause Alzheimer’s disease.

Review Date: 06/22/2010
Reviewed By: Harvey Simon, MD, Associate Professor of Medicine, Harvard Medical School; Physician, Massachusetts General Hospital. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.

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