Types of dementia
The most common types of dementia are Alzheimer's disease, vascular dementia (VD), dementia with Lewy bodies, and frontotemporal dementia.
Alzheimer’s disease is the most common type of dementia, accounting for about 50 to 70 per cent of dementia cases worldwide. It is characterised by short-term memory loss, apathy and depression in the early stages and progresses to decline in most cognitive functions in later stages. This form is most common among older people with dementia, particularly among women.
It is a deteriorating illness that attacks the brain. As the disease progresses abnormal material builds up as 'tangles' in the centre of the brain cells, and 'plagues' outside the brain cells. These disrupt messages within the brain, damaging connections between brain cells. The brain cells eventually die and this means that information cannot be recalled or assimilated. As Alzheimer’s disease affects each area of the brain, certain functions or abilities are progressively lost.
Vascular dementia is the broad term for dementia associated with problems of circulation of blood to the brain and is the second most common type of dementia, with about 20 to 30 per cent of dementia cases thought to be this type. The presentation of the disease is somewhat different from Alzheimer's disease because it affects different parts of the brain and cognitive functions although these two forms of dementia overlap and share a number of characteristics. It is caused by cerebrovascular conditions including stroke. Mood fluctuations are more common in vascular dementia than Alzheimer’s disease.
Frontotemporal dementia accounts for 5-10 per cent of dementia and is more common in males and has a younger onset. Early symptoms include personality and mood changes, and language difficulties.
Dementia with Lewy bodies
Dementia with Lewy bodies accounts for up to 5 per cent of dementia cases and is associated with the development of abnormal cells in the brain, called Lewy bodies. Symptoms for dementia with Lewy bodies include fluctuation in cognitive ability and visual hallucinations, as well as symptoms similar to Parkinson disease. Progression tends to be more rapid than Alzheimer's disease.
There are many different diagnostic types of dementia other than four main type of dementia described above. These include dementia associated with Parkinson’s disease, dementia associated with Huntington’s disease, dementia secondary to alcohol and/or drug abuse, HIV/AIDS related dementia, dementia secondary to Down’s syndrome, dementia associated with multiple sclerosis and prion diseases such as Creutzfeldt-Jakob disease.
(Resource: Dementia in Australia, AIHW, 2012, Alzhimer’s Australia)