A-103: Parkinson’s Disease Subtypes and the Relationship Between Category and Letter Fluency Performance

Abstract

Objective: Category but not letter fluency is diminished in Parkinson’s disease (PD). It’s unclear if these findings extend to subtypes defined by type of initial motor symptom. Individuals with an initial non-tremor (NT) motor symptoms (rigidity, akinesia, postural instability) tend to have greater cognitive deficits relative to those with tremor (T). We hypothesized that PD-related weaknesses on category fluency are driven by the NT subtype. Method/Data Selection: Fifty PD participants (NT=24,T=26) and 25 normal controls (NC) participated in this study. Participants were non-demented as indicated by an MMSE score above 26. Groups were statistically similar in regard to age (x-=66.85,SD=7.11), education (x-=16.57,SD=2.27), and sex (44% female). Participants completed DKEFS Verbal Fluency. PD groups had similar motor symptom severity as indicated by the unified Parkinson’s disease rating scale (x-=20.96,SD=13.59). Results/Data Synthesis: One-way ANOVAs indicated no group differences on letter fluency. On category fluency, group differences emerged at the 15-30, 30-45 and 45-60 second intervals (p-values <.05). At the 15-30 and 30-45 intervals the NT group performed significantly worse than the other groups. At the 45 to 60 second interval the T group performed worse than the NC group. Conclusions: PD has been associated with worse category fluency, relative to letter fluency. It is unclear if these findings are driven by cognitive differences between PD subtypes. In the present study, PD with initial non-tremor motor symptoms produced less words in category, but not letter fluency, compared to tremor subtype and controls. This difference may reflect greater disruption of semantic networks within this subtype.