The symptoms and impact of Parkinson's vary from person to person. 

• PD is most common in people over 60 years old, but there is a young-onset variation.

• Historically, it was thought to originate in the brain, but some researchers believe there is a variation that originates in the gut.

• A recent video about Parkinson's -- Link to YouTube     (An hour long, but good.) 

• A series of short videos (5 to 10  min) by the Veterans Admin.   VA YouTube 

Parkinson’s disease (PD) occurs when brain cells that make dopamine, a chemical that coordinates movement, stop working or die. Because PD can cause tremor, slowness, stiffness, and walking and balance problems, it is called a “movement disorder.” But constipation, depression, memory problems and other non-movement symptoms also can be part of Parkinson’s. PD is a lifelong and progressive disease, which means that symptoms slowly worsen over time.   https://www.michaeljfox.org/parkinsons-101 

"Your doctor may refer to a scale to help you understand the progression of the disease. Parkinson's stages correspond both to the severity of movement symptoms and to how much the disease affects a person’s daily activities. The most commonly used rating scales focus on motor symptoms. They are:

• The Hoehn and Yahr stages,  a rating scale used to describe how motor symptoms progress in PD.

  • On a scale of 1 to 5,  1 and 2 represent early-stage, 2 and 3 mid-stage, and 4 and 5 advanced-stage Parkinson's.

• The Unified Parkinson’s Disease Rating Scale (UPDRS) is a more comprehensive tool used to account for non-motor symptoms, including mental functioning, mood, and social interaction.

  • Accounts for cognitive difficulties, ability to carry out daily activities and treatment complications.

New scales include information on non-motor symptoms (such as sense of smell).

Symptoms and disease progression are unique to each person. Knowing the typical stages of Parkinson’s can help you cope with changes as they occur. Some people experience the changes over 20 years or more and may not progress to the final stage. Others find the disease progresses more quickly.

Additional information is available on the Parkinson's site:  Stages of Parkinson's.