It is characterized by loss of function and death of nerve cells in several areas of the brain, leading to loss of mental functions such as memory and learning. Alzheimer's disease is the most common cause of dementia.
Researchers have yet to learn what causes the disease.
It usually begins after age 65 but onset may occur as early as 40. The early symptoms of AD, which include forgetfulness and loss of concentration, can be easily missed, as they resemble natural signs of aging. One out of every 10 people over the age of 65 has Alzheimer's. A person with Alzheimer's lives an average of eight years and as many as 20 years from the onset of symptoms. Researchers at the University of South Florida have found a vaccine that can stop or slow Alzheimer's in mice that have been genetically engineered to develop the disease.