Cognitive Functional Abilities in Parkinson's Disease: Agreement Between Patients and Informants

Abstract

Background: The Penn Parkinson's Daily Activities Questionnaire-15 (PDAQ-15) assesses cognition-related instrumental activities of daily living (IADL) in Parkinson's disease (PD). Objectives: To assess the degree and predictors of disagreement between patients (PT) and knowledgeable informants (KI) on the PDAQ-15. Methods: We recruited 254 PT and KI pairs (PT-KI), determined predictors of agreement, and compared scores to a performance-based functional measure (Direct Assessment of Functional Status [DAFS]; N = 61). Results: PT and KI total score (intraclass correlation = 0.57) and individual item (Cohen's kappa = 0.46–0.62) agreement were moderate. Patient depression, global cognition, and caregiver burden (all P < 0.05), predicted PT-KI discrepancy. PT-KI discrepancy was highest in patients with a dementia diagnosis, followed by mild cognitive impairment and then normal cognition (all P < 0.01), with PT rating themselves relatively more functionally intact as cognition worsened. DAFS performance was more highly correlated with KI (r = 0.82; P < 0.001) than PT (r = 0.62; P < 0.001) PDAQ-15 score. Conclusions: Our results support using KI as proxies when assessing cognitive IADLs in PD PTs, particularly in cases of more advanced cognitive decline.