Relationship of Movement Disorders Society–Unified Parkinson's Disease Rating Scale Nonmotor Symptoms to Cognitive Functioning in Patients with Parkinson's Disease

Background: Few studies assess the relationships between nonmotor aspects of experiences of daily living and cognitive functioning in Parkinson's disease (PD). Objective: To evaluate the relationships among the Movement Disorders Society–Unified Parkinson's Disease Rating Scale (MDS-UPDRS) part I items and neuropsychological tests in PD.Methods: We assessed 151 PD patients with the MDS-UPDRS part I and a battery of cognitive tests focused on the following 5 cognitive domains: attention/working memory, executive functioning, recent memory, language, visuoperception. Raw scores for individual cognitive tests were transformed to z scores, and cognitive domain scores were calculated by averaging z scores within each domain. Individual items from the MDS-UPDRS part I were entered in a stepwise linear regression analysis assessing item contribution to cognitive domain scores. Results: The MDS-UPDRS part I item scores for hallucinations and psychosis and light headedness on standing predicted attention/working memory domain scores (P = 0.004). These same item scores, along with apathy, depressed mood, and dopamine dysregulation syndrome, predicted executive functioning (P = 0.044). The apathy and dopamine dysregulation syndrome items predicted language (P = 0.006). In addition, the cognitive impairment and sleep items were predictors of recent memory (P = 0.031). None of the items were predictors of visuoperception (P = 0.006). Other part I items were not significantly related to cognitive domain scores. Conclusions: Specific nonmotor MDS-UPDRS part I items, particularly mood, behavior, and autonomic-related items, exhibited significant relationships with cognitive domains. The highest number of items were predictive of the executive functioning domain, which is the hallmark cognitive dysfunction in PD.