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Government of

Information and public services for the Island of Jersey

L'înformâtion et les sèrvices publyis pouor I'Île dé Jèrri

Types and causes of dementia

What causes dementia ​

Although we don’t know exactly what causes dementia, some lifestyle factors such as smoking and obesity are being linked to an increased risk of developing the condition. 

Dementia may also be a result of other health problems, such as a stroke or mini-stroke, or may stand alone by itself. 

What happens to the brain if you have dementia​ 

Dementia changes the structure of the brain which results in the loss of nerve cells or neurons. This makes the ability to function in daily life increasingly difficult. ​

Alzheimer’s disease​

Alzheimer’s disease is the most common cause of dementia and accounts for approximately 55% of all cases.

What happens to the brain with Alzheimer’s disease​

Damage to brain cells and nerves causes disruption to the transmitters that carry messages to the brain, especially those responsible for storing memories, which means poor short term memory will often be the first sign of a problem. 

How to spot Alzheimer’s disease​ 

There will normally be evidence from a scan, normally a CT scan, which will show parts of the brain tissue that has shrunk. The scan will also show either localised or general damage to the brain.

Level of progression ​

The progression of Alzheimer’s disease is often slow, with a gradual decline in ability over many years. 

Vascular dementia ​

Damage to the brain as a result of strokes or a disease of cerebral blood vessels may result in vascular dementia. This is the second most common cause of dementia and accounts for approximately 20% of diagnoses. 

What happens to the brain with vascular dementia

The brain relies on a network of vessels to bring it oxygen bearing blood. If the oxygen supply to the brain fails, brain cells die, which can cause vascular dementia.  

How to spot vascular dementia​ 

Vascular dementia can often result in someone becoming more emotional, upset or angry than before. Symptoms can occur either suddenly after a full stroke, or over time through a series of small strokes. 

Level of progression​ 

Progression of vascular dementia is often less easy to predict. Progression is more stepwise than in Alzheimer’s and a pattern of good and bad days is common. 

Dementia with Lewy bodies (DLB)​

Dementia with Lewy bodies (DLB) is the third most common type of dementia, accounting for approximately 15% of diagnoses. 

What happens to the brain with DLB​

There will be distinct biochemical changes in the brain and impairment of brain function which can be detected on an EEG. 

How to spot DLB

Dementia with Lewy bodies may present symptoms such as:

  • problems with movement and proneness to falls
  • difficulty using common objects, eg a television remote
  • delusions or hallucinations
  • falling asleep suddenly and without warning 
  • becoming prone to short losses of consciousness 

These symptoms may be more prominent than memory loss, and diagnosis should carefully rule out other causes which may also cause movement problems, eg Parkinson’s disease. 

Fronto-temporal dementia (FTD), including Pick’s disease

Fronto-temporal dementia (FTD) is not common, accounting for about 5% of diagnoses in older people with cognitive problems. In people under 65 with cognitive problems, FTD accounts for around 20% of diagnoses. 

How to spot fronto-temporal dementia (FTD)

Diagnosis can be difficult to make, as onset is gradual and symptoms are often subtle and non-specific. Initially, problems are often unusual behaviours and problems with language; either talking too much or having difficulty in finding words.

A person with FTD will often either become more volatile, apathetic or lose interest and motivation. 

Rarer causes of dementia 

There are many other causes of dementia, including:

  • progressive supranuclear palsy (PSP)
  • Korsakoff’s syndrome
  • Binswanger’s disease
  • HIV 
  • Creutzfeldt-Jakob disease (CJD)

Those at risk of developing dementia 

People with multiple sclerosis, motor neurone disease, Parkinson’s disease or Down’s Syndrome all have an increased risk of developing dementia. 

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