(from L demens
) is progressive decline in cognitive function
due to damage or disease in the brain
beyond what might be expected from normal ageing. Particulary affected areas may be memory
and problem solving
, although particularly in the later stages of the condition, affected persons may be disoriented in time (not knowing what day, week, month or year it is), place (not knowing where they are) and person (not knowing who they are).
Affected person's may also show signs of psychosis and delirium.