Department of Health

Key messages

  • The symptoms of dementia vary depending on the form of dementia and the areas of the brain that are affected.
  • Behavioural and psychological symptoms, such as wandering, agitation, depression, aggression, social inappropriateness, repetitive behaviour, sleep disturbances and hallucinations affect up to 90 per cent of people with dementia.
  • Dementia usually progresses gradually from mild to severe.
  • There are many types of dementia. Alzheimer’s disease is the most common.

Dementia is generally under-recognised and under-diagnosed in the early stages of the disease because the signs are very subtle (1). An admission to hospital may be the first opportunity to initiate investigations that lead to a diagnosis and a greater understanding of how to support the person to maintain as much independence as possible during and after the admission.

Dementia is not one specific disease; it is an umbrella term to describe a set of symptoms caused by a number of neurological diseases that affect the brain and a person’s ability to think, remember, understand, make judgments, communicate, socially interact and perform everyday tasks.

The type of symptoms and how they develop vary depending on the form of dementia a person has and the areas of the brain that are damaged.

Dementia usually has a gradual onset and is progressive and irreversible.

Symptoms and signs

Most people are aware that dementia affects a person’s memory; in particular their short-term memory. It can also impact a person’s thinking, behaviour, movement and ability to do everyday tasks.

Symptoms and signs of dementia can include:

  • loss of insight, difficulty learning and following instructions
  • difficulty with language and comprehension
  • problems with calculation, judgment and reasoning
  • difficulty with decision making and concentration
  • lack of motivation, including apathy and withdrawal
  • change in their personality and social behaviour
  • problems with orientation to time and place
  • difficulty sequencing tasks, such as coordinating getting dressed
  • poor hygiene and dental care.

Behavioural and psychological symptoms of dementia (BPSD)

Changes in behaviour, such as wandering, pacing, agitation, depression, aggression, social inappropriateness, repetitive behaviour, sleep disturbances and hallucinations, are common in people with dementia - affecting up to 90 per cent of people with dementia.


The severity of dementia is commonly referred to as mild, moderate or severe:

  • Mild – at the early stage, deficits are noted in a number of areas but the person can function with minimal assistance.
  • Moderate – deficits become more obvious and greater levels of assistance are needed to help the person function.
  • Severe – the person is almost totally dependent on the care and supervision of others1.


There are many types of dementia. Alzheimer’s disease is the most common (50–70 per cent of all dementia cases worldwide); vascular dementia accounts for 20–30 per cent of cases, frontotemporal dementia accounts for 5–10 per cent of cases, and Dementia with Lewy bodies (DLB) accounts for 5 per cent of cases. Other types of dementia include younger onset dementia, alcohol-related dementia (Korsakoff’s Syndrome) and dementia in other diseases (such as Parkinson Disease, Huntington’s Disease, AIDS and Down syndrome). Mixed dementia may be more widespread with Alzheimer/vascular dementia accounting for 25 per cent of dementia cases and Alzheimer/DLB accounting for 15 per cent, particularly with increasing age.

1. Draper, B., Understanding Alzheimer's and other dementias 2011, Woollahra, NSW: Longueville Books.

Reviewed 05 October 2015


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