Parkinson’s is a neurodegenerative disease. Its symptoms become very significant when enough neuron damage occurs in the substantia nigra portion of the brain. When this region of the brain no longer produces enough of the neurotransmitter dopamine, severe defects in motor function result. Based on current research, other parts of the brain may become damaged first, resulting in less-recognized Parkinson’s symptoms such as loss of smell. Here are the stages of Parkinson’s per Parkinson.org:

Stage One
During this initial stage, the person has mild symptoms that generally do not interfere with daily activities. Tremor and other movement symptoms occur on one side of the body only. Friends and family may notice changes in posture, walking, and facial expressions.

Stage Two
In stage two of Parkinson’s, the symptoms start getting worse. Tremor, rigidity, and other movement symptoms affect both sides of the body. Walking problems and poor posture may become apparent. In this stage, the person is still able to live alone, but completing day-to-day tasks becomes more difficult and may take longer.
Stage Three
Stage three is considered mid-stage in the progression of the disease. Loss of balance and slowness of movements are hallmarks of this phase. Falls are more common. Though the person is still fully independent, symptoms significantly impair activities of daily living such as dressing and eating.
Stage Four
During this stage of Parkinson’s, symptoms are severe and very limiting. It’s possible to stand without assistance, but movement may require a walker. The person needs help with activities of daily living and is unable to live alone.
Stage Five
This is the most advanced and debilitating stage of Parkinson’s disease. Stiffness in the legs may make it impossible to stand or walk. The person requires a wheelchair or is bedridden. Around-the-clock nursing care is required for all activities. The person may experience hallucinations and delusions. While stage five focuses on motor symptoms, the Parkinson’s community acknowledges that there are many important non-motor symptoms as well.