The stages of Parkinson's correspond to the severity of movement symptoms and how much a person’s daily activities are affected. The most commonly used rating scales are focused on the motor symptoms, but new scales include information on non-motor symptoms (such as cognitive problems or sense of smell).
The Hoehn and Yahr scale rates symptoms on a scale of 1 to 5. On this scale, depending on a person’s difficulties, 1 and 2 represent early-stage, 2 and 3 mid-stage, and 4 and 5 advanced-stage Parkinson's.
Another scale commonly used to assess the progression of Parkinson's is the United Parkinson’s Disease Rating Scale (UPDRS). It focuses on movement symptoms. In addition to these, the UPDRS takes into account cognitive difficulties, ability to carry out daily activities, and treatment complications.
Mild Parkinson’s disease
Movement symptoms may be inconvenient, but do not affect daily activities.
Moderate Parkinson’s disease
Movement symptoms occur on both sides of the body and movements are more slowly. Trouble with balance and coordination may develop. Movements may become stuck ("freezing" episodes). Symptoms can reappear quickly and unexpectedly, which could be described as being like a light switch being turned on and off ("on/off" syndrome). Parkinson's medications may "wear off" between doses.
Advanced Parkinson’s disease
This stage corresponds to great difficulty with the ability to get up or walk. The patients might not be able to live alone and assistance is needed with all daily activities. Cognitive problems may be prominent, including hallucinations and delusions.
The beneficial effects of oral medication becomes unpredictable and is failing to control motor fluctuations. Other therapy strategies such as continuous drug delivery or stimulation have to be considered.