Multimethod assessment of everyday functioning and memory abilities in Parkinson's disease.

Objective: This study compared functional abilities in individuals with Parkinson's disease (PD) with normal cognition (PD-CN) and mild cognitive impairment (PD-MCI) using multiple assessment methods. Cognitive and physical correlates were also examined. Method: Participants were 42 nondemented individuals with PD (24 PD-CN, 18 PD-MCI) and 42 age-matched healthy controls. Functional abilities were assessed through direct observation and self-and informant-report questionnaires. Participants were administered an activity-based memory paradigm that assessed prospective, content, and temporal order memory as well as a test of mobility. Results: Compared to the PD-CN and healthy control groups, participants with PD-MCI performed significantly worse on directly observed everyday activities, self- and informant-reports of instrumental activities of daily living (IADLs), and self-report of everyday activities requiring physical capacity. No significant differences were observed between PD-CN and healthy controls. Among participants with PD, content memory correlated with all of the functional outcome measures, temporal order memory correlated with self-reported IADLs, and physical mobility correlated with self-reported physical capacity and content memory. Conclusions: The results indicated that PD-MCI is associated with decreased ability to perform everyday activities. Reduced ability to correctly recall and sequence activities may contribute to lower functional abilities on IADLs, whereas noncognitive factors (i.e., mobility) may become more salient when the everyday task requires physical capacity. The results from this study suggest that subtle cognitive impairments in Parkinson's disease are associated with lower functioning in daily life. Understanding the differential role of cognitive and physical limitations in Parkinson's disease may help identify those at risk for functional decline and improve interventions to promote functional independence.