Delirium is an acute disorder of attention, awareness, and altered mental status. It develops over a short period of time (usually hours to a few days) and tends to fluctuate in severity during the course of a day. Other key clinical features of delirium include disorganized thinking, altered level of consciousness, disorientation, memory impairment, perceptual disturbances (illusions or hallucinations) and delusions, increased or decreased psychomotor activity, and disturbance of the sleep–wake cycle.
People with delirium can present with hypoactive or hyperactive forms. In the hypoactive form, people present as lethargic, withdrawn, and sleepy, and their delirium often goes unrecognized by clinicians and caregivers. The hyperactive form is characterized by restlessness, agitation, being hyperalert, and often hallucinations and delusions. Many people may fluctuate between the two forms (mixed delirium).
A number of health conditions—including neurocognitive, mood, anxiety, and psychotic disorders—may mimic delirium and cause it to be overlooked or misdiagnosed. Distinguishing between these disorders can be especially difficult when people do not have family or caregivers available to provide knowledge of the person’s baseline mental status and when the changes occurred. Delirium can be easily overlooked in people living with dementia because some of the symptoms overlap, and many people have both conditions (22% to 89% of people in the community and hospital have both).
Although delirium may be caused by a single factor, it is more commonly the result of a combination of predisposing factors that make the person vulnerable (e.g., older age, coexisting medical conditions, dementia or cognitive impairment, depression, problems with hearing and vision) and exposure to acute precipitating factors or stresses (e.g., medications, malnutrition, acute illness, use of physical restraints, use of a bladder catheter, pain, sleep interruptions, surgery). In up to 30% of cases, no cause can be found.
Delirium is very common in older people in the hospital setting: overall occurrence rates range from 29% to 64%. Settings with the highest incidence rates include intensive care (19% to 82%), post-surgical care (11% to 51%), palliative care (42% to 88%), and long-term care or post-acute care (20% to 22%). The prevalence of delirium in the community setting is lower (1% to 2%), but its onset usually requires emergency care. Delirium is present in 8% to 17% of older people who present at the emergency department.
Delirium is an acute medical emergency that requires prompt recognition and treatment of underlying causes. Delirium has been identified as the third most common harmful event experienced by people admitted to Canadian hospitals. It has been associated with increased mortality across multiple care settings, including the emergency department, hospital acute care and intensive care units, and long-term care homes. Delirium is also linked to prolonged hospital length of stay and increased placement in long-term care homes after hospitalization. Delirium can be a stressful and frightening experience for the person and their family and caregivers, as well as for their health care providers.
An episode of delirium is often associated with decreased functional independence and cognitive decline (i.e., worsening of pre-existing cognitive impairment or dementia and increased risk of new-onset dementia). Prolonged delirium, in which the symptoms persist at or beyond discharge from hospital, may occur in 29% to 55% of patients. As many as 30% have persistent symptoms 6 months after discharge from hospital.
Despite the obvious burdens to individuals and to the health care system, delirium is often unrecognized, misdiagnosed as another disorder, or misattributed to dementia. Indeed, delirium is recognized in only about one-third of cases. However, early identification of risk factors is important because delirium can be prevented in 30% to 40% of cases, using preventive interventions. Guidelines support screening for those at risk, and tailored interventions can prevent and manage delirium. When symptoms of delirium are not identified early, assessment and treatment of the underlying causes and implementation of multicomponent management strategies are delayed.
Consulting with a medical specialist (i.e., geriatrician, geriatric psychiatrist) for older people who are undergoing emergency surgery can reduce the occurrence of delirium. Compared with usual care (reactive geriatric assessment), preoperative assessment and postoperative follow-up by a geriatrician have been shown to reduce the incidence of delirium by over one-third and reduce severe delirium by over one-half in people with a hip fracture.
When there are barriers to communication (e.g., language discordance, or hearing or speech impairments) delirium is more difficult to identify because many of the instruments used to screen for delirium rely on the ability to communicate. Barriers to communication can also hinder people’s understanding of specific information related to delirium and its ongoing management.
The Senior Friendly Hospital Strategy in Ontario has identified improvements in practices related to delirium, but also some variation in the spread of these practices within and among participating Ontario hospitals (135 hospitals across the province). As part of a broader strategy to improve the care of older adults who are hospitalized, the Senior Friendly Care (sfCare) Framework has been supporting best practices related to delirium. Following the implementation of the sfCare Framework, the percentage of participating hospitals reporting delirium screening and detection practices increased from 62% in 2011 to 92% in 2014. Hospitals reporting delirium prevention and management strategies increased from 62% in 2011 to 88% in 2014. Despite these improvements, in 2014, only 36% of participating hospitals reported spreading screening and detection practices across the entire organization, and only 23% reported spreading prevention and management practices across the entire organization.
Regional disparities also exist for access to specialty geriatric services and other providers who may have special expertise in identifying and managing delirium.