What causes Dementia?

By  , Expert Content
Feb 24, 2012

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Dementia is caused by injury or changes in the brain. There are many causes of dementia –some can be reversed with treatment but most cannot be.

Common causes of dementia which cannot be reversed with treatment include:

Alzheimer's disease: Alzheimer's disease is a brain disorder in which the brain cells degenerate and die, causing a steady decline in memory and mental function. Alzheimer's disease (AD) is the leading cause of mental decline, or dementia among older people.  People with dementia, as a result of Alzheimer's disease, can have problems with memory, thinking and behaviour. The symptoms develop slowly and worsen as the disease progresses and can become severe enough to interfere with daily tasks.

Parkinson's disease: It is type of movement disorder in which the person often develops dementia.

Vascular dementia: It is caused due to interruption of blood supply to the brain. Brain needs constant supply of oxygen and nutrients to function properly and be healthy. Any interruption in the supply of blood causes the brain cells to die, resulting in brain damage. In vascular dementia, the interruption to blood supply occurs gradually, if the vessels inside the brain are narrowed and hardened due to atherosclerosis.

Dementia with Lewy bodies: Lewy bodies are small, circular protein deposits which are formed inside the brain. The exact cause that leads to formation of lewy bodies is not known, and how the lewy bodies damage the brain and cause dementia is also not known. According to one hypothesis, they block the effects of two neurotransmitters called dopamine and acetylcholine. People having dementia with Lewy bodies tend to have frequent highly detailed visual hallucinations (seeing things that are not there). Usually people will see other people or animals that are not real and would have a tendency to fall frequently.

Fronto-temporal dementia: This type of dementia is caused by progressive damage and shrinking of two parts of the brain, the temporal lobe and the frontal lobe. Many people (40-50% of cases) with fronto-temporal dementia inherit a genetic mutation, i.e. an altered gene from their parents. Frontotemporal dementia may cause personality changes or unusual behaviour.  

Some less common cause of dementia are:

  • repeated head injury
  • infections of the brain, such as meningitis or encephalitis
  • Huntington's disease—it is a rare genetic condition which leads to progressive brain damage
  • Creutzfeldt-Jakob disease (CJD)--a rare and fatal condition in which the brain and nervous system are damaged
  • overactive or underactive thyroid gland
  • lack of vitamin B in the diet
  • lead poisoning, poisoning with pesticides
  • certain brain tumours
  • certain lung and heart conditions which cause interruption of supply of blood and oxygen to the brain.

Some causes of dementia which can be treated include:

  • Underactive thyroid gland (hypothyroidism).
  • Vitamin B12 deficiency.
  • Heavy-metal poisoning, such as from lead.
  • Side effects of medicines or drug interactions.
  • Certain brain tumours.
  • Chronic alcoholism.




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