Dementia (meaning "deprived of mind") is a cognitive impairment. It may be static, the result of a unique global brain injury or progressive, resulting in long-term decline in cognitive function due to damage or disease in the body beyond what might be expected from normal aging. Although dementia is far more common in the geriatric population, it may occur in any stage of adulthood. This age cut-off is defining, as similar sets of symptoms due to organic brain syndrome or dysfunction, are given different names in populations younger than adult. Up to the end of the nineteenth century, dementia was a much broader clinical concept.

Dementia is a non-specific illness syndrome (set of signs and symptoms) in which affected areas of cognition may be memory, attention, language, and problem solving. It is normally required to be present for at least 6 months to be diagnosed; cognitive dysfunction which has been seen only over shorter times, particularly less than weeks, must be termed delirium. In all types of general cognitive dysfunction...