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Delirium and dementia

2-minute read

Dementia is a condition where a person’s memory, thinking, understanding or judgement can be affected. It gets worse with time. People who have dementia are at a higher risk of developing delirium. Delirium is a more sudden change in consciousness or thinking that can often be prevented or treated.

What is delirium?

Delirium is where there is a recent change in a person's thinking and behaviour that can come and go. The person often has difficulty paying attention. They may be very sleepy or restless, or be thinking in a disorganised way.

Delirium often occurs in older people in hospital. People who have delirium when they are in hospital are at a higher risk of developing further medical complications.

What are the symptoms of delirium?

A person with delirium may be confused and have problems with memory, They may be agitated or drowsy.

Signs of delirium include:

  • having problems with memory, particularly of recent events
  • being disoriented, not knowing where they are, who they are or what time it is
  • problems with perception
  • rambling or incoherent speech
  • restlessness, agitation or aggression
  • having hallucinations (seeing or hearing something that's not there) or delusions
  • alternatively, being quiet, drowsy and lethargic

What are the causes of delirium?

Delirium can be caused by changes in a person's health, such as an infection or a medication change. It can also be caused by things such as constipation, dehydration and pain. Many people will have more than one problem leading to their delirium. Sometimes it is difficult to find the cause.

People with dementia, cognitive impairment, or hearing or vision loss are at an increased risk of delirium.

How is delirium diagnosed?

To diagnose delirium, a health worker may talk to family, friends or carers about changes in the person's behaviour or mental state. If there have been changes over a short period of time, the person might have delirium.

The health worker will also observe for changes in the person's consciousness and thought patterns. If someone is found to have delirium, further tests may be done to find the cause.

Management of delirium

It is important to try and find the cause of delirium and treat that. Always report increasing confusion in a hospitalised person to a health care worker. It can also be helpful to do simple things like removing excess noise and making sure the person:

If a person is a risk to themselves or others, medication is sometimes used.

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Last reviewed: May 2020


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Delirium and dementia

This Q&A sheet provides information about what delirium is, and, how it relates to people with dementia.

Read more on Dementia Australia website

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