Although Parkinson’s disease (PD) is progressive and worsens over time, it is highly individual and affects people differently. Not all people who have PD will experience all the symptoms, and symptoms may vary in their severity between patients. Different people experience progression at different speeds, as well. However, physicians have established stages that describe how the disease progresses. These five stages are known as the Hoehn and Yahr Scale used by physicians throughout the world to classify patients in research studies.1,2
- Stage One of Parkinson’s Disease – In stage one, the earliest stage, the symptoms of PD are mild and only seen on one side of the body (unilateral involvement), and there is usually minimal or no functional impairment. The symptoms of PD at stage one may be so mild that the person doesn’t seek medical attention or the physician is unable to make a diagnosis. Symptoms at stage one may include tremor, such as intermittent tremor of one hand, rigidity, or one hand or leg may feel more clumsy than another, or one side of the face may be affected, impacting the expression. This stage is very difficult to diagnose and a physician may wait to see if the symptoms get worse over time before making a formal diagnosis.
- Stage Two of Parkinson’s Disease – Stage two is still considered early disease in PD, and it is characterized by symptoms on both sides of the body (bilateral involvement) or at the midline without impairment to balance. Stage two may develop months or years after stage one. Symptoms of PD in stage two may include the loss of facial expression on both sides of the face, decreased blinking, speech abnormalities, soft voice, monotone voice, fading volume after starting to speak loudly, slurring speech, stiffness or rigidity of the muscles in the trunk that may result in neck or back pain, stooped posture, stooped posture, and general slowness in all activities of daily living. However, at this stage the individual is still able to perform tasks of daily living. Diagnosis may be easy at this stage if the patient has a tremor; however, if stage one was missed and the only symptoms of stage two are slowness or lack of spontaneous movement, PD could be misinterpreted as only advancing age.
- Stage Three of Parkinson’s Disease – Stage three is considered mid-stage and is characterized by loss of balance and slowness of movement. Balance is compromised by the inability to make the rapid, automatic and involuntary adjustments necessary to prevent falling, and falls are common at this stage. All other symptoms of PD are also present at this stage, and generally diagnosis is not in doubt at stage three. Often a physician will diagnose impairments in reflexes at this stage by standing behind the patient and gently pulling the shoulders to determine if the patient has trouble maintaining balance and falls backward (the physician of course will not let the patient fall). An important clarifying factor of stage three is that the patient is still fully independent in their daily living activities, such as dressing, hygiene, and eating.
- Stage Four of Parkinson’s Disease – In stage four, PD has progressed to a severely disabling disease. Patients with stage four PD may be able to walk and stand unassisted, but they are noticeably incapacitated. Many use a walker to help them. At this stage, the patient is unable to live an independent life and needs assistance with some activities of daily living. The necessity for help with daily living defines this stage. If the patient is still able to live alone, it is still defined as Stage Three.
- Stage Five of Parkinson’s Disease – Stage five is the most advanced and is characterized by an inability to rise from a chair or get out of bed without help, they may have a tendency to fall when standing or turning, and they may freeze or stumble when walking. Around-the-clock assistance is required at this stage to reduce the risk of falling and help the patient with all daily activities. At stage five, the patient may also experience hallucinations or delusions.
While the symptoms worsen over time, it is worth noting that some patients with PD never reach stage five. Also, the length of time to progress through the different stages varies from individual to individual. Not all the symptoms may occur in one individual either. For example, one person may have a tremor but balance remains intact. In addition, there are treatments available that can help at every stage of the disease. However, the earlier the diagnosis, and the earlier the stage at which the disease is diagnosed, the more effective the treatment is at alleviating symptoms.