[Definition and epidemiology of delirium in the elderly]

Delirium in the elderly is a transient, mostly reversible organic-mental syndrome with acute confusion, cognitive impairment, decline of vigilance, increased or reduced psychomotor activity and a disturbed sleep-wake-cycle. The etiology of delirium is multifactorial. The prevalence of delirium at hospital admission ranges from 14 to 24 percent. In addition, the incidence of developing delirium during hospitalisation ranges from 5 to 56 percent. Further, a close association between delirium and increased mortality rate has been documented. Unfortunately, if not specifically looked for, delirium often remains undiscovered by patients, physicians and nurses. Recent scientific work demonstrates the important effects of delirium both on an individual and societal level, as well as on the health-care system.