Dementia with Lewy bodies: what is it and what causes it?

Dementia with Lewy bodies (DLB) is a type of dementia that shares symptoms with both Alzheimer's disease and Parkinson's disease.

What is dementia with Lewy bodies?

Dementia with Lewy Bodies (DLB) may account for 10-15 per cent of all cases of dementia. DLB can be diagnosed wrongly and is often mistaken for Alzheimer's disease. 

DLB is sometimes known by other names. These include Lewy body dementia, Lewy body variant of Alzheimer's disease, diffuse Lewy body disease and cortical Lewy body disease. All these terms refer to the same condition.


What causes dementia with Lewy bodies?

Lewy bodies are named after the German doctor who first identified them. They are tiny deposits of a protein (alpha-synuclein) that appear in nerve cells in the brain. Researchers don't have a full understanding of why Lewy bodies appear, or exactly how they contribute to dementia. However, this is linked to two factors:

  • low levels of important chemicals (mainly acetylcholine and dopamine) that carry messages between nerve cells
  • a loss of connections between nerve cells, which then die.

Lewy bodies are the cause of DLB and Parkinson's disease. They are two of several diseases caused by Lewy bodies that affect the brain and nervous system and get worse over time. These are sometimes called Lewy body disorders. 

The way someone is affected by DLB will depend partly on where the Lewy bodies are in the brain: 

  • Lewy bodies at the base of the brain are closely linked to problems with movement (motor symptoms). These are the main feature of Parkinson's disease.
  • Lewy bodies in the outer layers of the brain are linked to problems with mental abilities (cognitive symptoms), which is a feature of DLB.

People with a Lewy body disorder can have problems with movement and changes in mental abilities at the same time.

A person with Parkinson's disease is at high risk of going on to develop dementia (Parkinson's disease dementia) as their condition progresses. Dementia may be more likely in a person who has developed Parkinson's later in life or who has been living with it for several years.

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