Objective: To consolidate the current literature pertaining to cognitive subtypes derived using data-driven methods in Parkinson’s Disease (PD).

Background: Recent application of the Mild Cognitive Impairment (MCI) concept to PD has proven valuable in identifying patients at risk of dementia. However, it has sparked controversy regarding the existence of cognitive subtypes. The present review critically synthesises current behavioural and neuroimaging literature exploring data-driven subtypes of cognition in PD.

Method: Following PRISMA guidelines, systematic literature searches for peer-reviewed articles on the topic of cognitive subtyping in PD were performed in October 2020 on Web of Science, PsycINFO, PubMed, and CINAHL databases. Articles that used data-driven methodology to derive cognitive subtypes were included. Study quality was assessed using the Newcastle-Ottawa Scale.

Results: Seventeen (17) relevant articles were included in the review: nine behavioural studies and eight neuroimaging studies. All studies were of moderate to high quality. Subtype structures showed either a spectrum of severity or specific domains of impairment. Domain-specific subtypes included the amnestic/non-amnestic and frontal/posterior dichotomies, as well as more complex structures with less definitive groupings. Neuroimaging evidence showed some support for a frontal/posterior distinction, although further evidence is needed to confirm the trajectories of these subtypes and their rates of cognitive decline. Finally, underlying factors contributing to the heterogeneity of the results were acknowledged (e.g., clustering methodology, sample characteristics).

Conclusion: Recurring themes of a memory-impaired group suggest clinical relevance of this cognitive subtype in PD. The current literature on cognitive subtyping in PD is limited but raises critical questions about the utility of data-driven subtyping methods and the influence of comorbid Alzheimer’s disease on results. Regardless, the results encourage further integration of neuroimaging research to define the latent neural mechanisms behind each subtype. While the scientific community has not yet reached consensus, there appears to be growing consistency and inherent value in identifying cognitive subtypes in PD.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/systematic-review-of-cognitive-subtypes-derived-from-data-driven-approaches-in-parkinsons-disease/