Delirium: an important (but often unrecognized) clinical syndrome.

Delirium is a clinical syndrome characterized by the acute onset of a disturbance in consciousness accompanied by a reduced ability to focus, sustain, or shift attention. It may foreshadow impending death in as many as 25% of hospitalized inpatients and may be a source of significant morbidity in those who present with this syndrome. The disorder may go unrecognized by hospital staff as well as those close to an affected individual, and this oversight may lead to poorer outcomes including longer lengths of stay in acute care hospitals, the need for nursing home placement, prolonged cognitive disturbances, and protracted disability. This paper will address this complex condition, focusing on its history, definition, epidemiology, pathophysiology, recognition, risk factors, and clinical quantification. Its prevention and treatment will be covered elsewhere in this journal.