Alzheimer disease is a degenerative disease of the brain that causes gradual loss of memory, judgment, and ability to function socially. Alzheimer disease currently affects about 5 million people. About 75 percent of Alzheimer disease cases are classified as sporadic, which means they occur in people with no history of the disorder in their family. Although the cause of these cases is unknown, genetic changes are likely to play a role. Virtually all sporadic Alzheimer disease begins after age 65, and the risk of developing this condition increases as a person gets older.
The remaining cases of Alzheimer disease are familial, which means they are found in multiple members of a family. Familial Alzheimer disease can be divided into early-onset disease (symptoms begin before age 65) and late-onset disease (symptoms begin after age 65).
Last updated: 7/2/2013
What is late-onset Alzheimer disease and how is it inherited?
Late-onset Alzheimer disease is a form of Alzheimer disease that begins to affect people after the age of 65. The genetic causes of late-onset Alzheimer disease are less clear. No gene that definitely causes the condition has been identified. However, a gene called APOE has been studied extensively as a risk factor for the disease. In particular, one form (or allele) of this gene seems to increase an individual's risk for developing type 2 Alzheimer disease.