AD is a progressive dementing illness in which the core symptom is memory loss. Other symptoms include impairments in language, abstract reasoning, and visual spatial abilities. Personality changes are common and range from apathy to restless agitation. Psychiatric symptoms, including depression, delusions, and hallucinations, may also occur during the course of AD. Symptoms worsen every year, and death usually occurs within ten years of initial onset.
AD is the most common cause of dementia in adults and is estimated to affect more than 2 million men and women over the age of 65 in the United States. The parts of the brain that direct cognition are especially affected, and definitive diagnosis of AD is only possible through autopsy.
Although the cause of AD is unknown, two risk factors have been identified: advanced age and genetic predisposition. The risk of developing AD is less than one percent before the age of 50, but increases to 30 percent in by the age of 90. The immediate relatives of patients have a 50 percent risk of developing the disease. Researchers found that one form of the gene apolipoprotein-E , on chromosome 19, seems to protect people from getting AD.
There are no treatments that reverse the illness or the retardation.