Although the exact cause of Alzheimer’s disease is unknown as of 2015, researchers believe that it's caused by a combination of age-related changes in the brain, genetics, and lifestyle and environmental factors, reports the National Institute on Aging. No one knows why the disease mainly strikes older people.
Even though the exact mechanisms are unclear, scientists believe that age-related changes to the brain cause harm to the brain’s neurons and contribute to the damage caused by Alzheimer’s disease, notes the National Institute on Aging. Progressive brain cell failure is the general prognosis for Alzheimer’s patients, reports the Alzheimer’s Association.
Growing old is the single biggest risk factor for developing the disease, according to the Alzheimer’s Association. The risk of developing Alzheimer’s doubles every year after age 65. By age 85, the risk of developing it increases to 50 percent. Still, Alzheimer’s is not considered to be a normal part of the aging process.
Alzheimer’s disease is more likely to develop in those with a family history of the disease affecting children, sisters, brothers or parents. Those with more than one member of the family with the disease are at added risk. Researchers have discovered a deterministic gene; those who in inherit the gene will eventually develop Alzheimer’s disease.