Dementia is a term used to describe a group of similar conditions characterised by the gradual impairment of brain function. It is commonly associated with memory loss, but can affect speech, cognition (thought), behaviour and mobility. An individual’s personality may also change, and health and functional ability decline as the condition progresses. 

While there are many forms of dementia, the most common is Alzheimer’s disease—a degenerative brain disease caused by nerve cell death resulting in shrinkage of the brain. Other major forms include: 

  • vascular dementia—mainly caused by haemodynamic (blood flow to the brain) disorders (for example, strokes); thromboembolism (small blood clots that block small blood vessels in the brain); small blood vessel disease in the brain; and bleeding into or around the brain
  • dementia with Lewy bodies—caused by the degeneration and death of nerve cells in the brain due to the presence of abnormal spherical structures, called Lewy bodies, which develop inside nerve cells
  • fronto-temporal dementia—caused by progressive damage to the frontal and/or temporal lobes of the brain. 

The boundaries between different forms of dementia are indistinct and it is possible for a person to have multiple (mixed) types of dementia at the same time.

Although dementia can affect younger people, it is increasingly common with advancing age and mainly occurs among those aged over 65. It is important to note that dementia is not an inevitable part of ageing. Dementia is a major cause of disability and dependency among older people. It not only affects individuals with the condition but it also has a substantial impact on their families and carers, as people with dementia eventually become dependent on their care providers in most, if not all, areas of daily living. 

The AIHW continues to work towards improving the quality and availability of national data on dementia.