Alternative names: Alzheimer’s disease, Chronic brain syndrome; Lewy body dementia; DLB; Vascular dementia 

Definition: Dementia is a loss of brain function. It is not a single disease. Instead, dementia refers to a group of illnesses that involve memory, behavior, learning, and communicating problems. The problems are progressive, which means they slowly get worse.


Causes, incidence, and risk factors: The two major causes of degenerative (non-reversible) dementia are Alzheimer’s disease and vascular dementia (loss of brain function due to a series of small strokes). Conditions that damage blood vessels or nerve structures of the brain can also lead to dementia. Treatable causes of dementia include normal pressure hydrocephalus, brain tumors, and dementia due to metabolic causes, thyroid conditions, low vitamin B12 levels, and infections.

Dementia may be diagnosed when a patient has two or more problems in brain function. Problems may involve language, memory, perception, emotional behavior or personality, and cognitive skills (such as calculation, abstract thinking, or judgment). Dementia usually first appears as forgetfulness. Other symptoms may only be seen during a medical exam or with cognitive tests.

Dementia usually occurs in older age. Dementia is rare in people under age 60. The risk for dementia increases as a person gets older.