A Comprehensive Meta-analysis on Short-term and Working Memory Dysfunction in Parkinson's Disease

Area of Science:

• Neuroscience
• Cognitive Psychology
• Neurology

Background:

• Previous meta-analyses indicated short-term memory (STM) and working memory (WM) dysfunction in Parkinson's disease (PD).
• Subsequent research has raised questions about the extent of these cognitive impairments in PD.
• A comprehensive quantitative review is needed to clarify the nature and moderators of STM and WM deficits in PD.

Purpose of the Study:

• To provide the largest statistical overview of STM and WM dysfunction in Parkinson's disease (PD).
• To identify moderating factors influencing the heterogeneity of effect sizes in PD-related cognitive deficits.
• To offer novel insights into the cognitive profile of individuals with PD.

Main Methods:

• A systematic literature search was conducted across major scientific databases (PubMed, PsycINFO, PsycArticles, Scopus, Web of Science).
• 350 effect sizes from 145 empirical studies comparing STM and WM scores in PD patients versus healthy controls were analyzed.
• Meta-regression and subgroup analyses were employed to investigate moderating factors.

Main Results:

• Patients with PD exhibited general dysfunction in visuospatial domains and impaired verbal working memory.
• Mild cognitive impairment was associated with difficulties in both STM and WM in PD patients.
• Disease duration significantly predicted visuospatial STM variance (R² = .8272).
• Higher daily levodopa equivalent doses correlated with WM dysfunction (verbal: R² = .1812; visuospatial: R² = .2340).
• Years of education partially explained verbal STM variance (R² = .1171).

Conclusions:

• This quantitative review confirms significant visuospatial STM and verbal WM deficits in Parkinson's disease.
• Cognitive status (mild cognitive impairment), disease duration, medication dosage, and educational background are key factors modulating these deficits.
• Findings provide a deeper understanding of cognitive functioning in PD and guide future research directions.