What is dementia?


What is dementia?

What is dementia?

Dementia is used to describe a general decline in all areas of mental ability. It is caused by brain injury or diseases such as Alzheimer’s.

What is dementia?


  • Dementia is a term used to describe a general decline in all areas of mental ability.
  • Symptoms include deterioration in mental processes including memory and language.
  • In the UK, dementia affects around 800,000 people.
  • About 60-80 per cent of dementia cases are the result of Alzheimer’s disease.

Alzheimer’s disease

  • Causes 60-80 per cent of dementia cases
  • Alzheimer’s causes tangles to form in the brain made from a protein called tau.
  • These tangles kill the nerve cells in the brain causing it to shrink.
  • This results initially in difficulties with day-to-day memory, problem solving and making decisions but can eventually lead to severe disorientation and confusion.

Vascular dementia

  • About 10 per cent of people with dementia have vascular dementia.
  • This is due to reduced blood flow to the brain because of blockages in the arteries leading up to the brain.
  • These blockages are usually a result of atherosclerosis, where blood vessels become clogged with fatty deposits, such as cholesterol.

Lewy body dementia

  • About 10 per cent of people with dementia have Lewy body dementia.
  • Lewy bodies are tiny spherical deposits of protein that form in the nerve cells of the brain.
  • It is not known exactly how these deposits form
  • The presence of Lewy bodies is linked to low levels of chemical messengers, such as dopamine, and a loss of communication between nerve cells.

Reversible dementia

  • Only about 10 per cent of dementia cases are treatable or potentially reversible.
  • In these cases the dementia is often caused by short-term illnesses such as vitamin B12 deficiency, a brain tumour, syphilis infection or alcohol dependence.

Pre-senile vs senile dementia

  • Traditionally, dementia was divided into ‘presenile’ or ‘senile’.
  • Presenile dementia has an onset before 65 years of age.
  • Senile dementia has an onset after 65 years of age.
  • This separation has helped in the search for genetic causes of early-onset Alzheimer’s.
  • An early diagnosis can help people with dementia get the right support, maintain their general wellbeing and help their close family and friends to prepare for the future.

This page was last updated on 2021-07-21

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