What does "dementia" mean and what are its common causes?

Dementia is a broad term for a group of symptoms affecting memory, thinking, and social abilities severely enough to interfere with daily life. The term comes from the Latin de meaning away from and mens meaning mind. It is not a specific disease but a syndrome caused by various brain disorders. Alzheimer's disease is the most common cause, accounting for 60 to 80 percent of cases, followed by vascular dementia from impaired blood flow to the brain, Lewy body dementia, and frontotemporal dementia.