dementia

Mental deterioration as a result of physical changes in the brain. It may be due to degenerative change, circulatory disease, infection, injury, or chronic poisoning. Senile dementia, a progressive loss of mental faculties such as memory and orientation, is typically a disease process of old age, and can be accompanied by depression. Alzheimer's disease is a form of dementia that has become more widespread in those countries where the life expectancy has increased in the 20th century.

Dementia is distinguished from amentia, or severe congenital (from birth) mental insufficiency.