Medical Research: What is the background for this study? What are the main findings?
Dr. Postuma: The background is that we often think about Parkinson’s Disease as a single disease. However, every clinician knows that there is a great deal of variability from patient to patient. If we can understand the main aspects that separate patients into groups, we can target therapy better.
The analysis used a semi-automated means to divide Parkinson’s patients into groups, using extensive information about motor and non-motor aspects of disease. We found that the non-motor symptoms, especially cognition, sleep disorders, and blood pressure changes were the most powerful predictors of which group a patient would be in. Based on these non-motor (and some motor aspects), the most accurate way to divide patients was into three groups – diffuse (many non-motor symptoms), pure motor, and intermediate (halfway between the other). We then followed patients over time. The diffuse group had, by far, the worse prognosis. This was not only for the non-motor aspects, but the motor as well.
Medical Research: What should clinicians and patients take away from your report?
Dr. Postuma: Most importantly, we can start to stratify patients into groups and predict their prognosis, based especially upon non-motor aspects of disease.
Not all patients are the same – if you are seeing mild cognitive changes, REM sleep behavior disorder, orthostatic hypotension and predominant gait dysfunction, prepare for a dramatically worse progression of disease, and be especially vigilant for cognitive changes.
Medical Research: What recommendations do you have for future research as a result of this study?
Dr. Postuma: The most critical thing is that these finding must be confirmed in other long term studies. Any patient population can have its own individual characters (for example, we think that because of the way we recruited patients, we may have had more of the ‘diffuse-malignant’ patients than other groups might have (for example, if they select highly-motivated cognitively well patients)). So, we have to see not only whether the classification holds up, but what the proportions in each group are.
Then, we have to start to understand why there is this variation. Is the underlying pathology different. Does genetics play a role (we already know that certain genetic causes have different phenotypes). Is it partially determined by the presence of other, even very early stage neurologic disease (like prodromal Alzheimer’s)? And finally, should these patients receive different types of therapy?
Ron Postuma, MD, MSc, Associate Professor, Department of Neurology, Montreal General Hospital, & Montreal, Quebec (2015). Parkinson’s Disease Can Be Stratified Into Three Distinct Groups