This study evaluates cognitive impairment in subjects with Parkinson disease (PD) and similar neurological disorder through obtaining longitudinal clinical and neuropsychological data. The long term goal is to have a well-characterized subject population to contribute to our understanding of the natural history, diagnosis and ultimate treatment of cognitive impairment in patients with PD and similar disorders.

The Pacific Northwest Udall Center (PANUC) Clinical Core has recruited and characterized a cohort of more than 600 individuals with Parkinson's disease (PD) during the initial funding period. Data from the PANUC Clinical Core, in collaboration with other Udall Centers and other academic medical centers, have helped confirm apolipoprotein E (APOE) (1) and glucocerebrosidase (glucosidase, beta, acid or GBA) (2)as genes that increase the risk and modify the phenotype (1) of cognitive decline in PD. Understanding the mechanisms underlying these gene effects is the focus of this renewal application, and the Clinical Core will provide well-characterized PD and control subjects of appropriate genotypes for PANUC projects. In addition, the majority of the existing cohort will be retained for additional longitudinal clinical and neuropsychological testing follow-up to support ongoing genetic and biomarker studies, with a refined battery of tests and a uniform biannual frequency of visits designed to maximize efficiency. Balance and gait testing (already piloted at the Portland site) will be added to the test battery for the entire cohort as an innovation that is thought to reflect higher order CNS function closely related to cognition. This innovation leverages the expertise of Dr. Horak, an investigator introduced to the PANUC by way of PANUC Pilot Award funding during the last funding period. As in the current cycle, Clinical Core subjects will be followed in identical fashion at two sites: one at UW directed by Dr. Hu, and the other at OHSU directed by Core Leader Dr. Quinn. Project 3 leader Dr. Horak will oversee balance and gait testing at OHSU and Dr. Kelly will oversee balance and gait testing at UW.

Inclusion Criteria:

• Diagnosis of Parkinson disease
• Over 18 years of age

Exclusion Criteria:

- Under 18 years of age

All subjects undergo the following procedures:

• Interview to collect data on medical history and demographics
• Neurological examination
• Questionnaires about mood, activities of daily living, and environmental exposures.
• Psychometric tests

Study companions might also be asked to complete questionnaires about the participant's thinking and memory, activities of daily living, sleep, and neuropsychiatric symptoms.