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 people with Parkinson's disease (PD) with psychosis (PDP). However, which key cognitive domains are differentially affected in PDP compared with those without (PDnP), remains unclear. Here, we examined this using a Bayesian meta-analytical 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 participants. Meta-analyses were conducted separately for each cognitive domain and subdomain, 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 with PDnP participants, 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 subdomains in PD psychosis, with global cognition, processing speed and executive functions as the most likely impaired. The presence of depression may influence task-related performance in PDP, alongside age and PD duration, but not dose of dopamine replacement treatments.

Parkinson's disease psychosis associated with accelerated multidomain cognitive decline.

BACKGROUND: Cognitive deficits are associated with poor quality of life and increased risk of development of dementia in patients with Parkinson's disease (PD) psychosis. The trajectory of cognitive decline in PD psychosis remains however unclear. OBJECTIVE: We examined this using data from the Parkinson's Progression Markers Initiative study. METHODS: We analysed data from patients with drug-naïve PD (n=676) and healthy controls (HC, n=187) over 5 years, and examined all cognitive measures assessed at each time point. We classified patients with PD into those who developed psychosis over the course of the study (PDP) and those without psychosis throughout (PDnP) using the Movement Disorders Society Unified Parkinson's Disease Rating Scale part I hallucinations/psychosis item. We used linear mixed-effect models with restricted maximum likelihood. Age, sex, ethnicity, education and neuropsychiatric and PD-specific symptoms were entered as covariates of interest. FINDINGS: There were no baseline cognitive differences between PD patient groups. There were differences in cognitive performance between PD and HC across the majority of the assessments.Patients with PDP exhibited greater cognitive decline over 5 years compared with PDnP across most domains even after controlling for sociodemographics, depression, sleepiness, rapid eye movement sleep behaviour disorder and motor symptom severity (immediate recall, b=-0.288, p=0.003; delayed recall, b=-0.146, p=0.003; global cognition, Montreal Cognitive Assessment, b=-0.206, p<0.001; visuospatial, b=-0.178, p=0.012; semantic fluency, b=-0.704, p=0.002; processing speed, b=-0.337, p=0.029). CONCLUSIONS: Patients with PD psychosis exhibited decline in semantic aspects of language, processing speed, global cognition, visuospatial abilities and memory, regardless of sociodemographic characteristics, neuropsychiatric and motor symptoms. These cognitive domains, particularly semantic aspects of language may therefore play an important role in PD psychosis and warrant further investigation. TRIAL REGISTRATION NUMBER: NCT01141023.