Delirium (acute confusional states), a common and often overlooked psychiatric disorder, can occur at any age, but elderly persons are especially prone to develop it. In later life, it is often a conspicuous feature of systemic or cerebral disease and drug (notably anticholinergic) toxicity, and it may constitute a grave prognostic sign. Its development in a hospitalized patient may interfere with his or her management, disrupt ward routine, and cause medicolegal complications as a result of patient injury. Acute onset of a fluctuating level of awareness, accompanied by sleep-wake cycle disruption, lethargy or agitation, and nocturnal worsening of symptoms, are diagnostic. Early recognition of delirium and treatment of its underlying cause are essential.
Lipowski ZJ. Delirium (Acute Confusional States). JAMA. 1987;258(13):1789-1792. doi:10.1001/jama.1987.03400130103041