Cognitive and executive impairments in Parkinson's Disease psychosis: a Bayesian meta-analysis

Background: Cognitive and executive deficits lead to worsening of quality of life and are a risk factor for developing dementia in Parkinson's Disease (PD) patients with psychosis. However, which key cognitive domains are differentially affected in PD patients with psychosis (PDP) compared to those without (PDnP), remains unclear. Here we examined this using a Bayesian meta-analytic approach. Methods: Searches were conducted on PubMed, Web of Science, SCOPUS, Medline and PsycINFO. Hedges' g effect-size estimates were extracted from eligible studies as a measure of standard mean differences between PDP and PDnP patients. Meta-analyses were conducted separately for each cognitive domain and sub-domain, we examined the effect of age, PD medications, PD duration and severity, depression and psychosis severity for all major domains with meta-regressions. Results: Effect-size estimates suggest worse performance on all major domains (k=105 studies) in PDP compared to PDnP patients, with global cognition (k=103 studies, g=-0.57), processing speed (k=29 studies, g=-0.58), executive functions (k=33, g=-0.56), episodic memory (k=30 studies, g=-0.58), and perception (k=34 studies, g=-0.55) as the most likely affected domains. Age, depression, and PD duration had moderating effects on task-related performance across most of the major nine domains. Conclusions: We report extensive deficits across nine domains as well as sub-domains in PD psychosis, with global cognition, processing speed and executive functions as the most likely impaired. Presence of depression may influence task-related performance in PDP, alongside age and PD duration, but not dose of dopamine replacement treatments.