Executive dysfunction in Parkinson's disease: A meta-analysis on the Wisconsin Card Sorting Test literature.

Executive dysfunctions are a frequently described non-motor symptom in patients with Parkinsonös disease (PD). However, the nature, extent, variability, and determinants of executive dysfunctions in PD are still poorly understood. To improve the characterization of executive dysfunctions in PD, we conducted a meta-analysis of the studies administering the Wisconsin Card Sorting Test (WCST) to patients with PD and healthy controls. We included k = 161 studies, which allowed us to precisely estimate the size of PD-related WCST deficits and to run powerful tests for potential moderators of these deficits. We found robust WCST deficits in PD, which were medium-to-large in size. These deficits were most pronounced in patients tested after withdrawal from dopaminergic medication and in samples characterized by severe motor impairment and long disease duration. Substantial WCST impairment was also detected in non-demented, non-depressed, and never-medicated patients with PD as well as after conservatively correcting for publication bias. Based on these findings, impaired WCST performance can be considered as a major hallmark of executive dysfunction in PD.