In common usage, delirium is often used to refer to drowsiness, disorientation, and hallucination. In medical terminology, however, a number of different symptoms, including temporary disturbance in consciousness, with reduced ability to focus attention and solve problems, are the core features of delirium. Occasionally sleeplessness and severe agitation and irritability are part of "delirium." Hallucination, drowsiness, and disorientation are not required, but may be contribute to the diagnosis.
The available data for the incidence and prevalence of delirium is varied. It appears that 15% to 30% of elderly patients will have delirium on admission to hospital and up to 56% will develop delirium during their stay.
Treatment of delirium involves two main strategies: first, treatment of the underlying presumed acute cause or causes; secondly, optimizing conditions for the brain. This involves ensuring that the patient with delirium has adequate oxygenation, hydration, nutrition, and normal levels of metabolites, that drug effects are minimized, constipation treated, pain treated, and so on. Detection and management of mental stress is also very important. Therefore, the traditional concept that the treatment of delirium is 'treat the cause' is not adequate; patients with delirium actually require a highly detailed and expert analysis of all the factors which might be disrupting brain function.
On Disease Delirium also found to worsen severity in those already diagnosed with dementia and increase the pace of cognitive decline because some delirium is preventable; it is plausible that delirium prevention may lead to dementia prevention.