A third of those affected by the disease go on to develop senile dementia . As the cells die, less dopamine is produced and transported to the striatum , the area of the brain that co-ordinates movement.
Symptoms develop as neurones die off and dopamine levels drop.
Parkinson's affects one to two people per 100,000 of the population. In the UK, 8000-10,000 people are diagnosed every year. However, some people have developed Parkinson's in their teens. The risk rises so that by the age of 80 more than two people per 100 of the population have developed some signs of the condition. Both sexes and all races appear to be equally affected.