Analysis of Parkinson's disease motor subtypes: Mexican Registry of Parkinson - ReMePARK

Background: Parkinson's disease (PD) is commonly classified into tremor dominant (TD) and a postural instability and gait disorder (PIGD) subtypes. Motor subtyping is primarily empirical. Data-driven approaches classify PD into multiple groups. Using hierarchical clustering to analyze the Parkinson's progression markers initiative cohort, we found five motor subtypes and an overall shift away from TD as disease progressed. However, replication is needed to validate results. Objective: To identify motor subtypes and analyze changes in a PD Mexican cohort utilizing a cluster analysis. Methods: We used the Mexican Registry of PD (ReMePARK). Scores to the motor components of the MDS-UPDRS Part II and III at all timepoints were utilized for the analysis. To identify motor subtypes without using a priori models, we applied correlational hierarchical clustering of the MDS-UPDRS scores. Names assigned to these groups were based on the MDS-UPDRS questions they each included. 197 patients were analyzed finding five groups: a TD group, an intermediate group (IG), and a PIGD group. Three subgroups within the IG emerged: axial, appendicular, and rigidity subgroup. We then assigned subtypes for each visit. Patients with inconsistent subtypes were analyzed separately by computing subtype frequencies over time using a bin width of 6 months to produce sample-level averages to document a change in subtype over time. Results: The motor subtype frequencies between 0 and 2 years of diagnosis were as follow: 60% TD, 0% axial, 14% appendicular, 5% rigidity, and 21% PIGD between 0 and 2 years of diagnosis. Linear regression showed that subtype increased (worsened) with disease duration p < 0.05. Of the patients resulting in subtypes that changed at 6-8 years of diagnosis (n = 77), frequencies were as follows: to 37% TD, 8% axial, 13% appendicular, 0% rigidity, and 42% PIGD. Conclusion: Five motor subtypes of PD patients resulted from our cluster analysis. Similar than our previous study. The overall shift away from TD was replicated in a cohort with 6-8 years of disease duration. Our results supports that disease duration may affect PD subtype. We replicated our previous study using the same systematic analysis with a different population.