Introduction: High-level language abilities tend to decline throughout the progression of Parkinson’s disease, but little is known about their deterioration rate. Since these abilities depend on executive functions, their decline may be related to the evolution of executive deficits. The main objective of this preliminary study was to determine if metaphor comprehension, a particularly sensitive high-level language ability, deteriorates over two years and whether this deterioration is related with an executive function decline.
Methods: Twelve patients with Parkinson’s disease and 13 controls completed a metaphor comprehension task, and different executive tasks at baseline (Parkinson’s disease and control groups) and two-year follow-up (group with Parkinson’s disease).
Results: Metaphor comprehension was impaired in Parkinson’s disease at baseline (p = .04; d = -1.22) and significantly deteriorates after two years (p < .0005; d = -1.03). However, this deterioration was not related with a decline in the executive functions tested.
Conclusion: Metaphor comprehension could be a marker that will help to monitor more precisely the cognitive deficits progression in Parkinson’s disease.