Department of Health

Key messages

  • Delirium affects up to 50 per cent of older people in certain hospital settings.
  • Older people with an existing cognitive impairment, such as dementia, experience higher rates of delirium so the care plan must address both conditions.
  • Older people who experience delirium are at greater risk of functional and cognitive decline and other adverse outcomes.
  • Delirium is often overlooked, not explored because clinicians think the patient has a pre-existing cognitive impairment, dismissed (“the patient is confused”) or poorly managed; this can have devastating outcomes for older patients and their families.

Studies have reported that:

  • older patients in surgical, palliative care and intensive care settings experience the highest rates of delirium1
  • patients may come to hospital with delirium or may develop delirium while in hospital2
  • patients are frequently discharged from hospital with persisting symptoms of delirium3
  • delirium is preventable in 30–40 per cent of cases3.

Older people who experience delirium are at greater risk of functional and cognitive decline, falls, hospital acquired infections, pressure injuries and incontinence. Delirium can cause longer lasting cognitive impairments in patients after surgery and may ‘lead to permanent cognitive decline and dementia in some patients’3. Delirium is also associated with higher mortality and morbidity, increased length of hospital stay and admission to residential care4,5.

Delirium can be caused by a range of factors

A range of factors affects an older person’s risk of developing delirium in hospital. Some factors are predisposing, that is they are related to characteristics of the person; some are precipitating, that is they are related to the person’s illness or the hospital environment. Delirium involves an interaction between the patient’s predisposing vulnerabilities, which puts them at greater risk when faced with precipitating factors.

Risk factors for delirium

Predisposing factors – related to the person

Precipitating factors – related to the illness or environment

Dementia or cognitive impairment

Older age (age 75 and older)

Functional impairment (mobility and decreased activities of daily living)

Visual or hearing impairment


Severe illness

History or previous episode of delirium


History of transient ischaemia or stroke

Alcohol misuse

Renal impairment

Malnutrition or dehydration


Medications – polypharmacy, psychoactive drugs, sedatives or hypnotics (high risk)

Use of an indwelling catheter

Physiological [electrolyte disturbances] (increased serum urea or BUN:creatinine ratio**; abnormal serum albumin, sodium, glucose or potassium; metabolic acidosis)

Infection (especially chest and urinary)

Use of physical restraint

Hospitalisation/length of stay

Any iatrogenic event

Surgery (aortic aneurysm, non-cardiac thoracic, neurosurgery)

Trauma or urgent admission


Malnutrition or dehydration



Alcohol withdrawal

Uncontrolled pain

Neurological insults

Sleep deprivation

Organ failure


* Comorbidity can be measured using the Charlson Comorbidity Index.

** BUN:creatinine ratio is the ratio of blood urea nitrogen (BUN) to serum creatinine and is used to determine acute kidney problems or dehydration. In Australia, it is referred to as urea:creatinine ratio.

1. Inouye, S.K., R.G.J. Westendorp, and J.S. Sacznski, Delirium in elderly people. The Lancet, 2014. 383: p. 911-922.

2. Travers, C., et al. Delirium in Australian Hospitals: A Prospective Study. Current Gerontology and Geriatics Research, 2013. 2013, 8.

3. Cole, M.G., Persistent delirium in older hospital patients. Curr Opin Psychiatry, 2010. 23(3): p. 250-254

4. Inouye, S., et al., Does delirium contribute to poor hospital outcomes? A three-site epidemiologic study. Journal of General Internal Medicine, 1998. 13(4): p. 234-42.

5. Wass, S., P.J. Webster, and R.N. Balakrishnan, Delirium in the elderly: a review. Oman Medical Journal, 2008. 23(3): p. 150-157.

Reviewed 05 October 2015


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