Three main types of Dementia

Alzheimer's Disease

Alzhemier’s disease is the most common type of dementia. In New Zealand, around 50 to 70 % of those with dementia have Alzheimer’s disease. In Alzheimer's disease, the number of nerve cells in the brain gradually reduces and the brain shrinks. The person with Alzheimer's therefore gets progressively worse as more cells are destroyed. The nerve signals that are essential for language and problem solving and controlling movements are impaired. During late stages of the

Symptoms of Alzheimer's disease:

• usually starts with forgetfulness
• problems working things out
• difficulty finding the right words
• changes in behaviour
• difficulty with everyday tasks; getting dressed and washing
• disorientation is common
• loss of sense of time and place
• confusion caused by new surroundings and people
• difficulty recognising previously well-known family and friends

Dementia with Lewy Bodies

Dementia with Lewy bodies may account for 10 to 15 per cent of all cases of dementia in older people. Lewy bodies are tiny protein deposits found in nerve cells. Their presence in the brain interrupts the action of chemical messengers, and disrupts its normal functioning.

With similarities to Alzheimer's and Parkinson's, it causes impairment of memory, language and reasoning. It can also affect areas of the brain that control movement and balance as well as vision and recognition of what we see.

People with Lewy body disease may have symptoms including:

• difficulty moving, resulting in falling and slowness
• problems judging differences
• hallucinations, causing the person to become agitated and disturbed
• abilities changing almost hourly, therefore an activity just carried out can later be unachievable.

Vascular Dementia

Sometimes called multi-infarct dementia, Vascular dementia accounts for 20 per cent of all dementias. It is caused by small blood vessels in the brain becoming blocked which prevents oxygen reaching nearby brain cells, leading eventually to their death.

It is likened to having many tiny strokes in the brain causing gradual decline in mental ability.

This type of dementia is usually identified by sudden changes in behaviour. The exact changes will depend on the area of the brain where the small strokes have occurred. As more of the brain is damaged by these strokes, the dementia starts to resemble Alzheimer's disease.

Vascular disease is treatable and treatment may help to reduce the risk of further incidents to the brain.

Other types of dementia

There are other types of dementia including fronto-temporal dementia (Pick's disease) which initially affects behaviour and personality more than memory, and alcohol-related dementia that is typically observed in middle age. There are also rarer causes of dementia, including progressive supranuclear palsy, Binswangers disease, HIV and Creutzfeldt-Jacob disease (CJD). People with multiple sclerosis, motor neurone disease, Parkinson's disease and Huntington's disease may also be more likely to develop dementia.