Prevalence, predictors, and emerging biomarkers for cognitive impairment and neuropsychiatric manifestations in Parkinson's disease in Africa: A systematic review.

BackgroundCognitive impairment and neuropsychiatric manifestations are common disabling non-motor symptoms that can negatively impact quality of life in Parkinson's disease. This review aimed to critically appraise and synthesize evidence on the prevalence, predictors, and emerging biomarkers of cognitive impairment and neuropsychiatric manifestations among patients with Parkinson's disease in Africa.MethodsWe conducted a systematic review of studies reporting cognitive and neuropsychiatric outcomes among individuals with Parkinson's disease in African populations, following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. We used the Critical Appraisal Skills Program checklist to determine the quality of the included studies. The Grading of Recommendations, Assessment, Development, and Evaluation approach was used to estimate the certainty of the evidence.ResultsA total of 32 studies, including 3687 patients, were analyzed. The prevalence of cognitive impairment ranged from 21.6% to 92%. Depression was the most common neuropsychiatric symptom (up to 81.7%). Consistent predictors of cognitive impairment included older age, advanced disease, and greater motor severity. Importantly, APOE ε4 homozygosity was associated with a twofold increase in the risk of cognitive impairment, while findings on LRRK2 G2019S mutations were heterogeneous across populations. Additionally, hypocalcemia and retinal nerve fiber layer thinning were linked to worse cognitive outcomes. Functional neuroimaging studies revealed altered emotional processing, with enhanced activation of limbic and cortical networks in response to positive emotional stimuli.ConclusionsEvidence from this review suggests that cognitive impairment and neuropsychiatric manifestations are common in African PD populations and may be associated with clinical, genetic, metabolic, and neurobiological factors, although the quality of the evidence is low. Larger, community-based, and longitudinal studies are warranted.