Delirium

Prevalence

Highest among hospitalized older individuals.
Varies depending on the individuals' characteristics, setting of care, and sensitivity of the detection method.
The prevalence of delirium in the community overall is low (1%-2%) but increases with age, rising to 14% among individuals older than 85 years.
The prevalence is 10%-30% in older individuals presenting to emergency departments, where the delirium often indicates a medical illness.
The prevalence of delirium when individuals are admitted to the hospital ranges from 14% to 24%, and estimates of the incidence of delirium arising during hospitalization range from 6% to 56% in general hospital populations.

Delirium may be increased in the context of:

Functional impairment.
Immobility.
History of falls.
Low levels of activity.
Use of drugs and medications with psychoactive properties (particularly alcohol and anticholinergics).

Both major and mild NCDs can increase the risk for delirium and complicate the course.
Older individuals are especially susceptible to delirium compared with younger adults.
Susceptibility to delirium in infancy and through childhood may be greater than in early and middle adulthood. In childhood, delirium may be related to febrile illnesses and certain medications (e.g., anticholinergics).

A disturbance in attention and awareness (reduced orientation to the environment).
The disturbance develops over a short period of time (usually hours to a few days), represents a change from baseline attention and awareness, and tends to fluctuate in severity during the course of a day.
An additional disturbance in cognition (e.g., memory deficit, disorientation, language, visuospatial ability, or perception).
The disturbances are not better explained by another preexisting, established, or evolving neurocognitive disorder and do not occur in the context of a severely reduced level of arousal, such as coma.
There is evidence from the history, physical examination, or laboratory findings that the disturbance is a direct physiological consequence of another medical condition, substance intoxication or withdrawal (i.e., due to a drug of abuse or to a medication), or exposure to a toxin, or is due to multiple etiologies.