What is Parkinson’s disease?
Parkinson's disease, or PD as it is sometimes referred to, is a progressive, neurological condition. It is predominantly characterised by difficulties with body movements, known as ‘motor symptoms’ – the most identifiable, perhaps, being tremor. Other difficulties that are not related to movement can also occur, such as pain, sleep disturbance and depression - these are known as ‘non-motor symptoms’.
According to the Global Declaration for Parkinson’s Disease, 6.3 million people have Parkinson's worldwide, affecting all races and cultures. The age of onset is usually over 60, but it is estimated that one in ten people are diagnosed before the age of 50, with slightly more men than women affected.
Parkinson’s is life-altering, but it is not life-threatening.
What causes Parkinson’s?
Our movements are controlled by nerve cells in the brain. To prompt a movement, the cells pass messages to one another - and to the rest of the body - using neurotransmitters. In healthy people, these messages are carried efficiently but, in people with Parkinson’s, the messages are disrupted and are not transmitted smoothly to the muscles. This is when difficulties controlling movement arise.
The messages fail to transmit properly because of a lack of dopamine - one of the neurotransmitters involved in the control of movement. In people with Parkinson’s, between 70 and 80% of the cells which produce dopamine have degenerated and been lost. This occurs mainly in a small section of the brain called the substantia nigra. If there is insufficient dopamine, nerve cells do not function properly and are unable to pass on the brain messages which results in Parkinson’s symptoms.
While dopamine is the main neurotransmitter involved, other neurotransmitter abnormalities also occur in Parkinson's. This is one explanation why simply replacing dopamine does not necessarily result in the benefits that might be expected. The abnormalities in other neurotransmitters may also explain why so many non-motor symptoms are present in Parkinson’s.
Why dopamine-producing cells become depleted is not clear. It is generally thought that multiple factors are responsible and areas of current research include ageing, genetic factors, environmental factors and viruses. It is also unclear why some people develop the disease but not others.