What is dementia?

Dementia is a brain condition, which causes a gradual loss of mental ability, including problems with memory, understanding, judgement, thinking and language.

Dementia is incurable and ultimately terminal. But early diagnosis can help manage the condition and improve people's lifestyles. Raising awareness about the condition can help people recognise the signs and symptoms and encourage them to visit their GP more quickly.

For more information about the symptoms of Dementia, visit our Recognising the signs of dementia page.

Causes of dementia

Dementia can be caused by various diseases or disorders which affect parts of the brain. The most common are below.

Alzheimer's disease

This accounts for over half of all cases of dementia. In Alzheimer's disease the brain shrinks and the numbers of nerve fibres in the brain gradually reduce. Some of the chemical signals produced in the brain also reduce and tiny deposits called plaques form throughout the brain.

Researchers do not know why these changes occur, or exactly how they cause dementia. Alzheimer's disease gradually progresses over time.

Visit our Alzheimer's disease stages page for more information about this cause of dementia.

Vascular dementia or blood vessel dementia

This is the second most common cause of dementia and is caused by a reduction of blood flow to the brain. This is often caused by a stroke or a series of small strokes, where brain cells are deprived of oxygen and die. This can occur in distinct parts of the brain, leaving other areas relatively unaffected.

Dementia with Lewy bodies

This is the third most common cause of dementia, causing around 15 in every 100 cases. Lewy bodies are tiny abnormal protein deposits that develop in nerve cells in the brain of people with this condition. It is not clear why the Lewy bodies develop but they interfere with the normal working of the brain.

Fronto-temporal dementia

Fronto-temporal dementia is a common cause of dementia in people under the age of 65. This type is caused by damage to areas of the brain responsible for behaviour, emotional responses and language.

Who gets dementia?

Unfortunately we don't know why some people develop dementia and others don't. We do know that several things can affect your risk of developing dementia. It's recommended that you: 

  • Eat a healthy diet;
  • Maintain a healthy weight;
  • Exercise regularly;
  • Don't drink too much alcohol;
  • Stop smoking (if you smoke);
  • Keep your blood pressure at a healthy level.

Dementia is increasingly common in older people. Between the age of 65 and 74, 1-2 people in 100 will have dementia, but by the age of 95, a quarter of people will have it. However, dementia is not a normal part of ageing.

Dementia is not inherited, but there is a small, increased risk if you have a relative with dementia. People with some conditions, such as Down's syndrome or Parkinson's disease, also have a higher risk of developing the condition.

For links to useful information, advice and support, visit our Resources for dementia page.