Objective: Identify discrete cognitive phenotypes in a cohort of 199 non-demented Parkinson’s disease (PD) patients.

Background: Methods to detect early cognitive decline and account for heterogeneity of deficits in PD are needed. Quantitative methods such as latent class analysis (LCA) offer an objective approach to delineate discrete phenotypes of impairment.

Methods: LCA was applied to a battery of eight neuropsychological measures to identify cognitive subtypes in non-demented PD patients enrolled in a longitudinal study of cognition (n=199). Two measures each were analyzed from four neurocognitive domains: executive function, memory, visuospatial function and language. Group differences in demographics, global cognition, everyday functioning, motor symptom severity, PD subtype (tremor-dominant versus postural instability/gait disturbance-dominant; PIGD) and consensus cognitive diagnosis based on Movement Disorders Society (MDS) criteria were examined.

Results: LCA identified 3 distinct groups: (1) intact cognition group (n=109; 54.8%); (2) amnestic group (n=64; 32.1%); and (3) mixed impairment (executive and language deficits) group (n=26; 13.1%). The amnestic group showed impaired free recall and recognition on a verbal memory task, but intact performance on other measures. The mixed impairment group had difficulty on measures of verbal fluency, visuoconstruction, and delayed free recall on a memory task, but intact recognition memory. Both impairment groups had significantly lower scores on measures of global cognition and ratings of everyday functioning, and greater motor symptoms, than the cognitively intact group. PD patients with PIGD subtype were more likely to be in one of the impaired groups. Of those with a consensus diagnosis of cognitively normal (n=151), LCA classified 35 (23.2%) patients as amnestic and 15 (9.9%) as mixed impairment.

Conclusions: Non-demented PD patients exhibit distinct neuropsychological profiles. One-third of patients with impairment as determined by LCA were diagnosed as cognitively intact by expert consensus, indicating that classification using a statistical algorithm may assist in detection of very early, subtle changes. Importantly, this study indicates that memory impairment is common even early on in the course of PD even when cognitive impairment is not clinically apparent.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/neuropsychological-subgroups-in-non-demented-parkinsons-disease-a-latent-class-analysis/