Abstract
In addition to the trademark motor symptoms present in Parkinson’s disease (PD), affected individuals are also susceptible to a range of cognitive dysfunctions which have adverse impacts on quality of life. The overarching aim of the current research was to characterize cognitive decline associated with PD over two time points separated by one year using a fully computerised cognitive battery, and to determine interrelationships with conventional measures of global cognitive functioning (Montreal Cognitive Assessment; MoCA) and motor impairment (Part III of the Unified Parkinson’s Disease Rating Scale; UPDRS), as well as other known factors associated with PD-related cognitive dysfunction including age, years of education, affective state, and sleep quality. The initial participant sample consisted of 51 PD patients and 48 healthy matched controls. Results showed that the PD group performed worse on all tasks in comparison to healthy matched controls, as determined by reaction times or accuracy rates, at both time points. Evidence of cognitive decline at follow-up was present for the PD group on only one task, which assessed inhibitory control, and an improvement across time points for both PD and control groups was found on a task assessing working memory, presumably reflecting benefits of practice. Higher MoCA scores were predictive of better performance on some tasks assessing inhibitory control, selective attention, and working memory, but this was not specific to the PD group. Older age was a significant predictor of poorer performance on all but one task. Surprisingly, other covariates – education, affective state, sleep quality, motor impairment, daily dosage of dopamine replacement medication, and impulsive-compulsive symptoms – generally had no relationship with cognitive performance. In summary, as predicted PD patients were found to have consistent deficits in multiple cognitive domains. Inconsistent with our hypotheses, there was a near absence of cognitive decline in the PD group across time points. Covariate measures varied widely in respect to their relationship with cognitive performance.