A data-driven approach to the study of heterogeneity in idiopathic Parkinson's disease: identification of three distinct subtypes

TLDR

Idiopathic Parkinson’s disease has been subclassified by motor symptoms, age at onset, depression, and cognition, yet these subgroups are often arbitrarily defined and lack reliable neuropathologic distinction. The study aimed to investigate IPD heterogeneity in a data‑driven manner. Researchers analyzed comprehensive demographic, motor, mood, and cognitive data from 176 IPD patients. Cluster analysis identified three subtypes—motor‑only, motor‑and‑cognitive, and rapid‑progression—at 5.6 years, with two subtypes at 13.4 years, showing distinct clinical progressions, no motor‑cognitive correlation, and suggesting independent neuropathologic processes.

Abstract

Idiopathic Parkinson's disease (IPD) has been subclassified on the basis of predominant motor symptomatology, age at disease onset, depressive affect, and cognitive performance. However, subgroups are usually arbitrarily defined and not reliably based on qualitatively distinct neuropathology. We explored heterogeneity in IPD in a data-driven manner using comprehensive demographic, motor, mood, and cognitive information collected from 176 patients with IPD. Cluster analysis revealed three subgroups of patients at a disease duration of 5.6 years and two subgroups at 13.4 years. The subgroups may represent the clinical progression of three distinct subtypes of IPD. The "motor only" subtype was characterized by motor symptom progression in the absence of intellectual impairment. Equivalent motor symptom progression was shown by the "motor and cognitive" subtype which was accompanied by executive function deficits progressing to global cognitive impairment. The "rapid progression" subtype was characterized by an older age at disease onset and rapidly progressive motor and cognitive disability. There was no relationship between the motor and cognitive symptoms in any subtype of IPD. We conclude that the clinical heterogeneity of IPD is governed by distinct neuropathologic processes with independent etiologic influences.