This systematic review only included studies that looked for an independent effect of delirium (i.e., after accounting for other associations with poor outcomes, for example co-morbidity or illness severity). In older persons admitted to hospital, individuals experiencing delirium are twice as likely to die than those who do not (meta-analysis of 12 studies). In the only prospective study conducted in the general population, older persons reporting delirium also showed higher mortality (60% increase). A large (N=82,770) two-centre study in unselected older emergency population found that delirium detected as part of normal care using the 4AT tool was strongly linked to 30-day mortality, hospital length of stay, and days at home in the year following the 4AT test date.Institutionalization was also twice as likely after an admission with delirium (meta-analysis of 7 studies). In a community-based population examining individuals after an episode of severe infection (though not specifically delirium), these persons acquired more functional limitations (i.e. required more assistance with their care needs) than those not experiencing infection. After an episode of delirium in the general population, functional dependence increased threefold.The association between delirium and dementia is complex. The systematic review estimated a 13-fold increase in dementia after delirium (meta-analysis of 2 studies). However, it is difficult to be certain that this is accurate because the population admitted to hospital includes persons with undiagnosed dementia (i.e. the dementia was present before the delirium, rather than caused by it).
Memory impairment: Memory impairment is linked to inattention, especially reduced formation of new long-term memory where higher degrees of attention is more necessary than for short-term memory. Since older memories are retained without need of concentration, previously formed long-term memories (i.e. those formed before the onset of delirium) are usually preserved in all but the most severe cases of delirium. Disorientation: As another symptom of confusion, and usually a more severe one, this describes the loss of awareness of the surroundings, environment and context in which the person exists. One may be disoriented to time, place, or self. Disorganized thinking: Disorganized thinking is usually noticed with speech that makes limited sense with apparent irrelevancies, and can involve poverty of speech, loose associations, perseveration, tangentiality, and other signs of a formal thought disorder. Language disturbances: Anomic aphasia, paraphasia, impaired comprehension, agraphia, and word-finding difficulties all involve impairment of linguistic information processing. Sleep changes: Sleep disturbances in delirium reflect disturbed circadian rhythm regulation, typically involving fragmented sleep or even sleep-wake cycle reversal (i.e. active at night, sleeping during the day) and often preceding the onset of a delirium episode
Psychotic symptoms: Symptoms of psychosis include suspiciousness, overvalued ideation and frank delusions. Delusions are typically poorly formed and less stereotyped than in schizophrenia or Alzheimers disease. They usually relate to persecutory themes of impending danger or threat in the immediate environment (e.g. being poisoned by nurses). Mood lability: Distortions to perceived or communicated emotional states as well as fluctuating emotional states can manifest in a delirious person (e.g.