Senility is a less preferred term for dementia, as it implies that confusion in an older person is a normal part of aging. Dementia is an abnormality at any age. The disease occurs in 10 percent of those over age 65 and 45 percent of those over age 85. The time can range from two to 20 years, depending on the age and other health factors of the individual. The disease associated with arteriosclerosis is stroke.
Strokes are the second most common cause of brain failure.
Sufferers are sometimes wrongly thought to be acting deliberately when they display annoying behavior. Alzheimer's and other forms of dementia are the result of a disease process, and though more common with advancing age, they are not a normal part of growing older. The cause of Alzheimer's disease is unknown. It appears that acetylcholine and other chemicals in the brain play a role in Alzheimer's disease. Exposure to aluminum and dental fillings have been mentioned as possible causes, but current evidence does not support these theories.