Below is an instruction from Human. Write a response.
    ### Instruction:
    What is (are) Parkinson's Disease ?
    ### Response:
    A Brain Disorder Parkinson's disease is a brain disorder that leads to shaking, stiffness, and difficulty with walking, balance, and coordination. It affects about half a million people in the United States although the numbers may be much higher. The average age of onset is 60 years, and the risk of developing Parkinson's goes up with age.
    