According to the Alzheimer’s Association, people with a parent or sibling with Alzheimer’s disease are more likely to develop the disease than those who do not have a first-degree relative with Alzheimer’s. In addition, those who have more than one first-degree relative with Alzheimer’s are at an even greater risk of getting Alzheimer’s.
Though family history is not necessary for an individual to develop Alzheimer’s, the AA notes that researchers have identified hereditary Alzheimer’s genes. For example, researchers estimate that between 40 and 65 percent of people diagnosed with Alzheimer’s have the APOE-e4 gene.
APOE-e4 is characterized as a risk gene because it increases the likelihood of developing Alzheimer’s but does not guarantee it will happen. The gene is inherited from a parent, and people who inherit two copies of APOE-e4 from their mother and father have a higher risk for Alzheimer’s than those who inherit one copy of the gene from their mother or father.
The AA also notes that researchers have found deterministic genes that cause Alzheimer’s. However, these genes are rare and have only been found in a few hundred families across the globe, accounting for 1 percent or less of all Alzheimer’s cases.