Introduction Introduction: Cognitive dysfunction is common in Parkinson's disease (PD) and associated with reduced functional abilities and increased dependence. To date, however, little is known about the relationship between performance of instrumental activities of daily living (IADLs) and cognitive stages in PD, and there are conflicting reports as to whether declines in specific cognitive domains predict IADL impairment. Methods Methods: Participants with PD were drawn from the Pacific Udall Center and included in the study if both participant and study partner IADL ratings and cognitive tests were completed (n = 192). Logistic regression analyses were performed to determine whether participant and/or study partner rating predicted mild cognitive impairment or dementia. Correlations are reported for the relationship between participant/study partner IADL reports as well as for specific cognitive tests.
ResultsResults: Although both participant and study partner ratings of IADL performance were associated with a diagnosis of PD with dementia, only participant self-rating of functional ability was significantly associated with a diagnosis of PD with mild cognitive impairment. Functional ability correlated most strongly with measures of processing speed, auditory working memory, and immediate verbal recall for both the participant and study partner ratings. Conclusion Conclusion: For participants with PD in the early stages of cognitive decline, self-rating may be more sensitive to the impact of cognitive changes on IADL function than ratings made by a knowledgeable study partner. Changes in executive function, processing speed, and learning may indicate a higher likelihood of IADL impairment. Careful assessment of cognition and IADL performance is recommended to permit individualized interventions prior to significant disability.Cognitive impairment is pervasive in Parkinson's disease (PD), often resulting in devastating impacts on quality of life, functional performance, and independence. 1 A decline in the ability to perform instrumental activities of daily living (IADL) related to cognitive impairment, although often initially subtle, can negatively impact disease outcome if not identified and adequately compensated. 2 Although significant functional impairment may be more apparent in PD-related dementia (PDD), subtle deficits in complex IADLs occur frequently among those with PDrelated mild cognitive impairment (PD-MCI), and the presence of such deficits may help to reveal the presence of early cognitive decline. 3 The assessment of functional change in PD presents challenges, however. Performance-based measures are not often