No one single factor has been determined as the cause of dementia. It is likely that a combination of factors, including age, genetic inheritance and environmental factors, are responsible. Some of the most common forms are:
This is the most common form of dementia - around two-thirds of people with dementia have Alzheimer's disease. Although we are still learning about the causes, there are typical changes seen in the brain - shrinkage and a build-up of abnormal proteins (plaques and tangles).
Alzheimer’s disease is progressive, starting as forgetfulness and mild confusion, progressing to memory loss, disorientation and changes in personality and behaviour. The specific symptoms can vary, depending on the part of the brain that is affected.
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This is the second most common form of dementia. This group of conditions is caused by poor blood supply to the brain as a result of a stroke or several mini-strokes, or by the slow accumulation of blood vessel disease in the brain. Vascular dementia symptoms can begin suddenly after a stroke or gradually as disease in the blood vessels worsen. Some people will have both vascular dementia and Alzheimer’s disease.
Lewy Body disease
This condition is characterised by the presence of ‘Lewy Bodies’, which are abnormal clumps of protein in the brain. These cause changes in movement, thinking, behaviour and alertness. People with Lewy Body disease can fluctuate between almost normal functioning and severe confusion within short periods, and may also have hallucinations, seeing things that aren't really there.
Fronto-temporal dementia is a group of conditions which affect the frontal and/or temporal lobes of the brain. If a person has affected frontal lobes they will have increasing difficulty with motivation, planning and organising, controlling emotions and maintaining socially appropriate behaviour. If temporal lobes are affected the person will have difficulty with speaking and/or understanding language. Symptoms often begin in a person's 50s or 60s.