Neuropsychiatric Predictors of Cognitive Decline in Parkinson Disease: A Longitudinal Study.

OBJECTIVES: To examine the relationship between anxiety, depression, apathy, and cognitive decline in Parkinson disease (PD). DESIGN: Longitudinal study design to assess whether specific neuropsychiatric, demographic, and clinical features predict future cognitive decline. SETTING: Veterans Affairs San Diego Medical Center and the University of California, San Diego. PARTICIPANTS: PD patients (N = 68) and healthy controls (N = 30). MEASUREMENTS: Participants were administered self-report measures of depression (Geriatric Depression Scale), anxiety (State Trait Anxiety Scale), and apathy (Apathy Scale), and a comprehensive neuropsychological battery assessing attention, language, visuospatial function, verbal and visual learning and memory, and executive function. Participants were tested at baseline and after an approximate 2-year period. RESULTS: Anxiety and depression at baseline were the strongest predictors of longitudinal decline on measures of verbal and visual learning, over and above other clinical and demographic characteristics. However, baseline neuropsychiatric symptoms did not significantly correlate with decline in other cognitive domains. No significant correlations were detected between neuropsychiatric symptoms and cognition in the healthy control group. CONCLUSIONS: These results suggest that anxiety and depression in PD may be risk factors for subsequent declines in learning. Emerging evidence suggests nonmotor symptoms are critical determinants of PD prognosis, and the results of this study highlight the importance of assessment of depression and anxiety early in PD.