Assessment of cognitive-driven activity of daily living impairment in non-demented Parkinson's patients

The core criterion for Parkinson's disease dementia (PDD) is the impairment in activities of daily living (ADL) function primarily caused by cognitive, not motor symptoms. There is evidence to assume that mild ADL impairments in mild cognitive impairment (PD-MCI) characterize those patients at high risk for dementia. Data of 216 Parkinson's disease (PD) patients assessed with comprehensive motor and neuropsychological assessments were analysed. Based on linear regression models, subscores of the Functional Activities Questionnaire (FAQ) primarily reflecting patients' global cognitive status (FAQ(C)) or PD-related motor severity (FAQ(M)) were developed. A quotient (FAQ(Q)) of both scores was calculated, with values >1 indicating more cognitive- compared to motor-driven ADL impairment. Both FAQ(C) and FAQ(M) scores were higher in PD-MCI than cognitively normal (PD-CN) patients, indicating more severe cognitive- and motor-driven ADL impairments in this group. One third (31.6%) of the PD-MCI group had a FAQ(Q) score >1, which was significantly different from patients with PD-CN (p = .02). PD-MCI patients with an FAQ(Q) score >1 were more impaired on tests assessing attention (p = .019) and language (p = .033) compared to PD-MCI patients with lower FAQ(Q) values. The differentiation between cognitive- and motor-driven ADL is important, as the loss of functional capacity is the defining factor for a diagnosis of PDD. We were able to differentiate the cognitive-driven from the motor-driven ADL impairments for the FAQ. PD-MCI patients with more cognitive- compared to motor-driven ADL impairments may pose a risk group for conversion to PDD and can be targeted for early treatments.