Apathy, but not depression, reflects inefficient cognitive strategies in Parkinson's disease

Abstract

Background: The relationship between apathy, depression and cognitive impairment in Parkinson's disease (PD) is still controversial. The objective of this study is to investigate whether apathy and depression are associated with inefficient cognitive strategies in PD.

Methods: In this prospective clinical cohort study conducted in a university-based clinical and research movement disorders center we studied 48 PD patients. Based on clinical evaluation, they were classified in two groups: PD with apathy (PD-A group, n = 23) and PD without apathy (PD-NA group, n = 25). Patients received clinical and neuropsychological evaluations. The clinical evaluation included: Apathy Evaluation Scale-patient version, Hamilton Depression Rating Scale-17 items, the Unified Parkinson's Disease Rating Scale and the Hoehn and Yahr staging system; the neuropsychological evaluation explored speed information processing, attention, working memory, executive function, learning abilities and memory, which included several measures of recall (immediate free, short delay free, long delay free and cued, and total recall).

Findings: PD-A and PD-NA groups did not differ in age, disease duration, treatment, and motor condition, but differed in recall (p<0.001) and executive tasks (p<0.001). Immediate free recall had the highest predictive value for apathy (F = 10.94; p = 0.002). Depression and apathy had a weak correlation (Pearson index= 0.3; p<0.07), with three items of the depression scale correlating with apathy (Pearson index between .3 and.4; p<0.04). The depressed and non-depressed PD patients within the non-apathetic group did not differ.

Conclusion: Apathy, but not depression, is associated with deficit in implementing efficient cognitive strategies. As the implementation of efficient strategies relies on the fronto-striatal circuit, we conclude that apathy, unlike depression, is an early expression of executive impairment in PD.

Figure 1. Recall and executive profiles of non-apathetic PD patients with and without depression.

The scores are expressed as mean score (the bar shows the standard error). None of the comparisons reaches the statistical significance. CVLT-TS =  California Verbal Learning Test II-Total recall score; CVLT-SFR: California Verbal Learning Test II-Short free recall; CVLT-LFR =  California Verbal Learning Test II-Long free recall; CVLT-LCR =  California Verbal Learning Test II-Long cued recall; CVLT-Rec =  California Verbal Learning Test II-Recognition; WCST-TC =  Wisconsin Card Sorting Test- Total correct; WCST-PR =  Wisconsin Card Sorting Test-Perseverative responses; WCST-NoPR =  Wisconsin Card Sorting Test- Non-perseverative responses; WCST-Cat =  Wisconsin Card Sorting Test- Categories completed.