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Is Alzheimer's Disease Genetic?

Researchers do not know the exact cause of Alzheimer's disease, but it is most likely due to a combination of a variety of genetic and other factors. Genetic research is concentrating on the role of heredity -- the transmission of qualities and illnesses from parents to children -- in determining risk for, and development of, Alzheimer's disease.

Alzheimer's disease strikes early and fairly often in certain families, often enough to be singled out as a separate form of the disease and given a label: early-onset familial Alzheimer's disease, or FAD. Combing through the DNA of these families, researchers have found an abnormality in one gene on chromosome 21 that is common to a few of the families. And they have linked a much larger proportion of early-onset families to recently identified and related genes on chromosomes 1 and 14.

The chromosome 21 gene also intrigues Alzheimer's researchers because of its role in Down syndrome. People with Down syndrome have an extra copy of chromosome 21 and, as they grow older, usually develop abnormalities in the brain like those found in Alzheimer's disease.

Few researchers think that the search for Alzheimer's genes is over. Most investigators are convinced that there are many more genes involved in Alzheimer's disease and, moreover, that other conditions must also be present for the disease to develop.