Researchers do not know the exact cause of Alzheimer’s disease, but it is most likely the result of a variety of factors including genetics. Genetic research has turned up that there could be a link between Alzheimer’s disease and the genes on four chromosomes labeled 1, 14, 19, and 21. Scientists who study the genetics of Alzheimer’s disease differentiate between familial Alzheimer’s disease (FAD) which runs in families and sporadic Alzheimer’s disease which does not seem to have as obvious an inheritance pattern.
Most of the cases of Alzheimer’s are the sporadic kind known as late-onset Alzheimer’s. This form does not seem to be a hereditary disease from what researchers know. In recent studies conducted scientists have found that the gene located on chromosome 19 known as APOE has been linked to late-onset Alzheimer’s. Many studies around the globe have confirmed that the inheritance of one of the variants of the APOE gene, APOE4, does increase the lifetime risk of developing Alzheimer’s. However, there are certain people with the APOE4 gene that do not develop Alzheimer’s. Scientists have determined that APOE4 is not a consistent genetic marker for the disease.
Less than ten percent of cases are familial Alzheimer’s disease. FAD has been found to strike early and fairly often in certain families, making it appear to have a hereditary factor. Research on the DNA of families who have experienced FAD has found an abnormality in one gene on chromosome 21 in some families. There are also links to the genes on chromosomes 1 and 14 in FAD cases. There is much research on Alzheimer’s and its heredity going on today. With time it is quite possibly that scientist will be able to determine more of the genetics of Alzheimer’s disease.