Registered Nurses' Association of Ontario

Nursing Best Practice Guidelines

What is Delirium?

Delirium is a temporary disordered mental state, characterized by acute and sudden onset of cognitive impairment, disorientation, disturbances in attention, decline in level of consciousness or perceptual disturbance. A prevalent disorder, it is estimated that 14 to 80 percent of all elderly clients hospitalized for the treatment of acute physical illnesses experience an episode of delirium. Studies have shown a marked variability in the epidemiology of delirium results from the differences in study populations, diagnostic criteria, case finding and research techniques (Foreman, Wakefield, Culp & Milisen, 2001).