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What causes dementia?

Dementia is an umbrella term that describes a collection of symptoms, not one specific disease. There are more than 100 different diseases that cause dementia. The most common are Alzheimer’s disease, vascular dementia and Lewy body disease.

Alzheimer’s disease

Alzheimer’s disease is the most common form of dementia. It is more common in older people than younger people, usually coming on after the age of 65. More than 70% of people with dementia have Alzheimer’s disease .

A few people develop Alzheimer’s disease while much younger. It is likely that these people have inherited Alzheimer’s disease due to problems with one or more of their genes.

People with Alzheimer’s disease have, scattered through their brains, deposits of certain proteins and other material that shouldn’t be there. It is likely that these deposits interfere with the way a person thinks and uses their memory.

Apart from the few cases of familial Alzheimer’s disease (Alzheimer’s that is inherited through a faulty gene), the causes of Alzheimer’s disease are unknown.

Alzheimer’s disease results in a progressive worsening of symptoms and death usually within 7 to 10 years.

Vascular dementia

Vascular dementia refers to dementia associated with problems in the circulation of blood to the brain. Some people develop dementia after having lots of small strokes, many of which they would not have even noticed. This is called multi-infarct dementia.

Some people develop dementia because of poor blood flow to the brain, usually due to high blood pressure and thickened arteries. This is called Binswanger's disease or subcortical vascular dementia.

People can also develop dementia after having one large stroke.

Lewy body disease

Lewy body disease is a common form of dementia, similar to Alzheimer’s disease. It is caused by the degeneration and death of nerve cells in the brain. Lewy bodies are unusual round objects that develop within cells in the brain. They probably play a role in killing these cells. It is not clear why they form, nor exactly what they do. It seems they are not inherited.

Frontotemporal dementia

In this type of dementia, the front and/or sides of the brain are affected more than the back of the brain or the central areas.

Frontotemporal dementias begin more often in the 40s and 50s than other types of dementia. They are also more likely to have a genetic element.

People with these types of dementia are particularly prone to problems with:

  • their mood
  • their judgement
  • their behaviour
  • their self-control
  • their hearing
  • their speech.

Expert advice - is dementia inevitable?

Although dementia is associated with ageing, it is not inevitable. Learn more from an expert about the risk factors of dementia such as ageing, smoking and high cholesterol and blood pressure.


Read the related video transcript

Last reviewed: November 2016

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Alzheimer's Australia | Areas of dementia research

Researchers are currently investigating a number of aspects of dementia. Research into the causes of dementia There is still much to learn about the possible causes of dementia, including Alzheimer's disease - the most common form of dementia.

Read more on Alzheimer's Australia website

Alzheimer's Australia | About dementia

Information The information in this section defines dementia, describes the symptoms and causes of dementia and explains the difference between normal memory problems and dementia. What is dementia? What is younger onset dementia?

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Alzheimer's Australia | Vascular dementia

Vascular dementia is the second most common cause of dementia after Alzheimer's disease. What is vascular dementia? Vascular dementia is the broad term for dementia associated with problems of circulation of blood to the brain. Are there different types of vascular dementia? There are a number of different types of Vascular dementia. Two of the most common are Multi-infarct dementia and Binswanger's disease.

Read more on Alzheimer's Australia website

Alzheimer's Australia | What is dementia?

Information The information in this section defines dementia, describes the symptoms and causes of dementia and explains the difference between normal memory problems and dementia. What is dementia? Dementia describes a collection of symptoms that are caused by disorders affecting the brain. It is not one specific disease. Dementia affects thinking, behaviour and the ability to perform everyday tasks. Brain function is affected enough to interfere with the persons normal social or working life.

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Alzheimer's Australia | Lewy Body disease resources

Lewy body disease is a common neurodegenerative disease of ageing. It affects over 100,000 Australians. Lewy body disease causes gradual brain damage. For reasons not fully understood, it occurs when there is an abnormal build up of a protein called alphasynuclein in brain cells. These abnormalities occur in specific areas of the brain, causing changes in movement, thinking and behaviour. Lewy body disease is one of the most prevalent causes of dementia, but unlike Alzheimer's disease, it is not well known.

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Dementia - Alzheimer's disease

Alzheimer’s disease is a physical disease of the brain with progressive damage that causes dementia. Some risk factors can lower your risk or delay the onset of dementia. Visiting a doctor is critical for an early diagnosis.

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Creutzfeldt–Jakob disease (CJD) is a fatal, degenerative brain disorder that causes rapidly progressive dementia and loss of muscle control. It is a rare disease, affecting 1–2 people in every million in Australia.

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Alzheimer's Australia | Types of dementia

Dementia is the umbrella term for a number of neurological conditions, of which the major symptom includes a global decline in brain function. It is a condition that has been noted in people for hundreds of years. Dementia was a relatively rare occurrence before the 20th century as fewer people lived to old age in pre-industrial society. It was not until the mid 1970s that dementia begun to be described as we know it today. We now know dementia is a disease symptom, and not a normal part of aging.

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The importance of early diagnosis of dementia and information about the diagnosis process. This information may be helpful to people who have concerns about dementia or to those who are concerned about their family members or friends.

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