What factors can predict Parkinson’s disease progression?
People with Parkinson’s disease (PD) reasonably want to know how their disease will progress over time. Unfortunately, it is very hard to predict how any individual person’s PD will evolve, and neurologists often refrain from answering these questions.
The Hoehn and Yahr Scale: Uses and Setbacks
To quantify disease progression, there is a commonly referenced staging scale. However, the staging of Parkinson’s disease does have significant drawbacks. The Hoehn and Yahr scale was developed by Drs. Margaret Hoehn and Melvin Yahr in 1967:
- Stage I: Symptoms involve one side of the body
- Stage 2: Symptoms involve both sides of the body, or the midline (that is, symptoms affect structures in the middle of the body such as speech abnormalities)
- Stage 3: Symptoms involve both sides of the body, with impairment of balance
- Stage 4: Symptoms have advanced to the point that although the person can stand and walk without the help of another person, he/she has significant disability. People in this stage typically need at least some help to perform their activities of daily living, or self-care activities such as eating, bathing, dressing, and toileting.
- Stage 5: The person cannot stand or walk without the help of another person
Hoehn and Yahr Scale Doesn’t Factor in Progression of Non-motor Symptoms
The Hoehn and Yahr scale focuses solely on the progression of motor symptoms and does not consider the psychiatric, cognitive, and autonomic non-motor symptoms that often cause more disability than motor symptoms as PD advances. This is a major limitation of the Hoehn and Yahr scale.
For example, someone may be considered Stage 3 on this scale, but have as many difficulties as someone who is at Stage 4 because of dysregulated blood pressure control or a mood disorder. Unfortunately, scales that also quantify the non-motor symptoms have not been developed, and therefore figuring out what stage of PD correlates with what level of actual disability is not straightforward.
In addition, there is no set timeline for how a person progresses through the Hoehn and Yahr stages. For example, many people stay at Stage 2 for a long time, perhaps decades. Many never progress beyond Stage 3. They may develop other health issues as they age which become more prominent than PD. While it is understandable for people with PD to want to prepare for the future, it is not possible, in many cases, to provide this information.
Subtypes of Parkinson’s Disease and Progression
What does seem to hold true for many people with PD (although not all!) is that a person’s rate of progression is typically stable over time. Someone who has had a slow rate of progression in the past tends to have a slow rate of progression overall.
Although the progression of PD can’t be determined exactly for any individual, researchers have tried to associate certain clinical features with rates of progression in the general PD population.
Tremor-predominant PD versus postural instability and gait disorder (PIGD) PD
In the past, several major types of Parkinson’s disease were identified:
- Tremor-Predominant Subtype: tremor is the first and most characteristic feature
- Rigidity/Hypokinesia Subtype: slowness and stiffness are the most characteristic features. Those with the rigidity/hypokinesia subtype were shown to have a faster motor progression than those with the tremor-predominant subtype
- Postural Instability and Gait Disorder (PIGD): balance and walking problems are the most prominent features. This subtype overlaps the rigidity/hypokinesia subtype. Studies also support the conclusion that those with the PIGD subtype experience more rapid motor decline than those with tremor-predominant PD
Diagnosis in middle age versus diagnosis in older age
Another area of research is the association between age of onset of PD and disease progression. One representative study, for example, showed that people who developed PD at an older age (greater than 78) had more motor impairment than people who developed PD in middle age (43-66) after the same amount of disease duration. The older group tended to have more stiffness, slowness, and problems with balance and gait than their younger counterparts at a comparable point after PD diagnosis.
Read more about How Parkinson’s Disease Is Diagnosed
Low non-motor symptom burden at diagnosis versus high non-motor symptom burden at diagnosis
Researchers have incorporated non-motor symptoms into the analyses of disease progression. For example, studies showed that patients with the PIGD subtype of PD who showed a faster progression of motor symptoms were also more likely to develop dementia than those with the tremor-predominant subtype.
Most recently, research into understanding PD progression has grown to include an analysis of a more complex array of non-motor features of PD. For example, one study identified three groups of newly diagnosed people with PD for whom significant amounts of information regarding motor and non-motor symptoms were collected using various validated scales.
These individuals were then followed over time:
- The first group demonstrated primarily motor features at the time of diagnosis, without significant non-motor features. This group had the slowest progression.
- The second group demonstrated more significant non-motor symptom burden at the time of diagnosis including apathy, pain, fatigue, sleepiness, depression, anxiety, autonomic dysfunction (including orthostatic hypotension, constipation, and urinary dysfunction), and certain measures of cognitive dysfunction. They also demonstrated more PIGD motor features on diagnosis. Overall, this group had the fastest progression.
- The third group had intermediate scores on the non-motor scales and demonstrated an intermediate rate of progression.
This study emphasized that non-motor burden is a vital part of predicting disease progression and that those who do not have non-motor symptoms at diagnosis tend to have a slower progression overall than those who have non-motor symptom burden at diagnosis
Can you change your PD progression?
It is important to remember that the studies mentioned above focus on the overall population of people with PD and the progression of any individual will not necessarily follow these rules. In addition, remember what is in your power to control – and that is physical exercise and healthy lifestyle choices. It is never too late to make positive lifestyle changes. Even small changes and adjustments can have a beneficial impact. Please refer to these articles to remind yourself of the ways that you may be able to influence the progression of your PD:
Tips and takeaways
- Although it is very difficult to predict the exact progression of PD in any given person, some generalities do hold true. For example, past rate of progression tends to predict future rate of progression
- Individuals with tremor-predominant symptoms at diagnosis tend to have slower motor progression than those with balance and gait predominant symptoms.
- People who are diagnosed in middle age or earlier tend to have slower motor progression than those diagnosed later in life.
- Individuals who do not have non-motor symptoms at diagnosis tend to have a slower progression overall than those who have non-motor symptom burden at diagnosis.
- Remember: exercise and healthy lifestyle choices may positively impact your PD progression!