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.