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What is Parkinson's disease?
Parkinson's disease is a condition in which parts of the brain become progressively damaged over many years, according to the NHS website.
What are the symptoms?
The NHS says there are three major symptoms, including tremors or shaking, slowness of movement and muscle stiffness.
Other symptoms include problems with balance, loss of smell, nerve pain, excessive sweating and dizziness.
Some people can also experience lack of sleep, excessive production of saliva and problems swallowing, causing malnutrition and dehydration.
What are the early signs?
Symptoms can start gradually, sometimes beginning with a barely noticeable tremor in just one part of the body.
In the early stages, people may show little or no expression, and their arms may not swing when they walk.
Speech can also become soft or slurred, with the condition worsening over time.
What are the causes?
Some scientists believe a combination of genetic and environmental factors are the cause of Parkinson's disease.
It occurs after a person experiences loss of nerve cells in a part of their brain.
However, it is not known why the loss of nerve cells associated with the condition takes place but research is ongoing to identify potential causes.
Scientists say genetics factor can increase a person's risk of developing the disease, and can therefore run in families.
Other factors attributed to causing the condition include environmental problems such as pollution, though such links are inconclusive, the NHS says.
How is it diagnosed?
No tests can conclusively
