Motor Phenotype Transitions in Parkinson's Disease and Their Association With Cognitive Decline: A Narrative Review

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Parkinson’s disease is clinically heterogeneous, with variation in motor manifestations and cognitive outcomes. This narrative review synthesises evidence on the classification of motor phenotypes, their longitudinal stability, factors associated with transitions between subtypes, and the potential relationship between such transitions and cognitive decline. The literature indicates that phenotype classification may change over time and that the postural instability and gait difficulty phenotype is associated with less favourable cognitive outcomes. However, evidence that subtype transition itself independently predicts cognitive decline remains limited and heterogeneous. Longitudinal studies with standardised repeated assessment of motor phenotypes and cognitive outcomes are needed to clarify its prognostic value.