There is an accompanying change in at least one other area that may include memory and learning (particularly recent memory), disorientation (particularly to time and place), alteration in language, or perceptual distortion or a perceptual-motor disturbance (Crite- rion C). The perceptual disturbances accompanying delirium include misinterpretations, illusions, or hallucinations; these disturbances are typically visual, but may occur in other modalities as well, and range from simple and uniform to highly complex. Normal atten- tion/arousal, delirium, and coma lie on a continuum, with coma defined as the lack of any response to verbal stimuli. The ability to evaluate cognition to diagnose delirium depends on there being a level of arousal sufficient for response to verbal stimulation; hence, delir- ium should not be diagnosed in the context of coma (Criterion D). Many noncomatose pa- tients have a reduced level of arousal. Those patients who show only minimal responses to verbal stimulation are incapable of engaging with attempts at standardized testing or even interview. This inability to engage should be classified as severe inattention. Low-arousal states (of acute onset) should be recognized as indicating severe inattention and cognitive change, and hence delirium. They are clinically indistinguishable from delirium diag- nosed on the basis of inattention or cognitive change elicited through cognitive testing and interview.
Delirium is often associated with a disturbance in the sleep-wake cycle. This disturbance can include daytime sleepiness, nighttime agitation, difficulty falling asleep, excessive sleepiness throughout the day, or wakefulness throughout the night. In some cases, com- plete reversal of the night-day sleep-wake cycle can occur. Sleep—wake cycle disturbances are very common in delirium and have been proposed as a core criterion for the diagnosis.
The individual with delirium may exhibit emotional disturbances, such as anxiety, fear, depression, irritability, anger, euphoria, and apathy. There may be rapid and unpre- dictable shifts from one emotional state to another. The disturbed emotional state may also be evident in calling out, screaming, cursing, muttering, moaning, or making other sounds. These behaviors are especially prevalent at night and under conditions in which stimulation and environmental cues are lacking.
The prevalence of delirium is highest among hospitalized older individuals and varies depending on the individuals’ characteristics, setting of care, and sensitivity of the detec- tion method. The prevalence of delirium in the community overall is low (1%—2%) but in- creases 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 occurs in 15%—53% of older individuals postoperatively and in 70%—87% of those in intensive care. Delirium oc- curs in up to 60% of individuals in nursing homes or post—acute care settings and in up to 83% of all individuals at the end of life.
While the majority of individuals with delirium have a full recovery with or without treatment, early recognition and intervention usually shortens the duration of the delir- ium. Delirium may progress to stupor, coma, seizures, or death, particularly if the under- lying cause remains untreated. Mortality among hospitalized individuals with delirium is high, and as many as 40% of individuals with delirium, particularly those with malignan- cies and other significant underlying medical illness, die within a year after diagnosis.
Environmental. Delirium may be increased in the context of functional impairment, im- mobility, a history of falls, low levels of activity, and use of drugs and medications with psychoactive properties (particularly alcohol and anticholinergics).