Pattern of executive impairment in mild to moderate Parkinson's disease.

BACKGROUND/AIMS: The exact pattern of impairment in executive functions (EF) among people with Parkinson's disease (PD) is still debated. Using a data-driven approach we investigated which areas of EF are particularly problematic in mild to moderate PD.

METHODS: Thirty-four patients with mild to moderate PD, who scored in the normal range on general cognition screening tests, but displayed frontal-type deficits indicated by Frontal Assessment Battery screening, completed the 9 tests that comprise the Delis-Kaplan Executive Function System. Patterns of performance were explored using cluster analysis and principal component analysis (PCA), and the frequency of impairments was established using normative data.

RESULTS: Both cluster analysis and PCA identified two distinct groups of EF tests. The first group included tests requiring time-efficient attentional control (e.g. the Trail Making test). The second group included tests measuring abstract reasoning and concept formation abilities (e.g. the 20 Questions test). Impairment was more frequent on the attentional control tests than on the abstract thinking tests.

CONCLUSION: PD pathology in the mild to moderate PD appears to affect the attentional control aspect of EF to a greater extent than abstract reasoning. Understanding the nature of executive deficits in PD is important for the development of targeted pharmacological and cognitive interventions for cognitive disturbances.