Parkinson’s Disease Patient Information Fact Sheet

What is Parkinson’s disease?
Parkinson’s disease is a progressive disease of the nervous system. In the United States, 50,000 to 60,000 new cases of Parkinson’s disease are diagnosed each year, adding to the one million people who currently have Parkinson’s disease. In fact, it is estimated that 4 to 6 million people around the world suffer from the condition. Parkinson’s disease becomes more common with increasing age, though there are those diagnosed with early- or young-onset Parkinson’s disease, perhaps actor Michael J. Fox being the most famous. He was diagnosed at age 30 and has raised awareness and research for this disease via his foundation.

Symptoms of the disease usually first appear in people over the age of 50, although as noted above, younger people can also develop the disease. There is no evidence that Parkinson’s disease is hereditary, although in around 5% of cases there is another family member affected. It is believed that genetics may make some people more prone to developing Parkinson’s disease, but only if combined with exposure to external factors. To date, scientists have identified nine genes linked to Parkinson’s disease.

What are the symptoms of Parkinson’s disease?
The main symptoms of Parkinson’s disease are tremor, stiff muscles and joints, and slowness or difficulty in walking. In most people the presenting symptom of the disease is tremor, which usually begins on one side of the body (unilaterally) in the hand or arm. The tremor usually occurs at rest and decreases when the affected part is being used. It usually increases during times of stress or heightened emotion and decreases during sleep. Stiffness or rigidity of the muscles can also occur; this can be quite painful and can cause difficulty in performing many everyday motions. Walking may be slowed and it can be difficult to start to walk. A lack of coordination may also cause problems. Other symptoms include difficulties with balance, speech and writing, and sometimes a lack of facial expression, altered posture and fatigue.Some people may also experience non-motor symptoms such as cognitive impairment, mood disorders, sleep difficulties, loss of smell, constipation, and drooling.

What causes Parkinson’s disease?
The reasons people develop Parkinson’s disease are not yet fully known. However, it is known that it is caused by a decrease in the nerve cells in a particular area of the brain called the substantia nigra. These cells produce and store dopamine, a chemical messenger involved in the coordination of movements in the body. The amount of dopamine being produced is therefore reduced while the level of acetylcholine, another chemical messenger, remains normal, causing an imbalance between the two. Symptoms of Parkinson’s disease usually appear when around 80% of the dopamine-producing cells have been lost.