The term "dementia" is used to describe the gradual deterioration of "intellectual" abilities and behavior that eventually interferes with customary daily living activities. "Customary daily living activities" include balancing the checkbook, keeping house, driving the car, involvement in social activities, and working at one's usual occupation. There may also be changes in personality and emotions. Contrary to popular belief, dementia is not a normal outcome of aging, but is caused by diseases that affect the brain. Dementia influences all aspects of mind and behavior, including memory, judgment, language, concentration, visual perception, temperament, and social interactions. Although dementia symptoms are eventually obvious to everyone, in the early stages special evaluations are necessary to demonstrate the abnormalities.
In people over the age of 65, the most common cause of dementia is Alzheimer's disease. Alzheimer's disease is a form of brain degeneration in which abnormal particles called neurofibrillary tangles and neuritic plaques form in the brain and destroy healthy neurons (brain cells). These abnormalities tend to settle in brain areas that control the ability to learn a new fact and remember it 30 minutes, or a day later, a skill we refer to as "memory". Years of studying dementias have shown that Alzheimer's disease is not the only type of brain degeneration. There are other forms of brain degeneration, many of which can affect people in their 50's or even 40's.