Parkinson’s Disease: Causes, Symptoms, and Complications Parkinson’s Disease is a challenging condition that affects movement, balance, and coordination, often starting with a barely noticeable tremor in one hand. This progressive disorder can lead to various complications, including difficulty thinking, swallowing, and sleeping. It is the second most common brain disorder in the United States that affects movement. Most people with PD are 60 years or older, but about 5 to 10 percent are diagnosed before they turn 50. While around 500,000 Americans