Can Physical Exercise Be Considered as a Promising Enhancer of Global Cognition in People with Parkinson's Disease? Results of a Systematic Review and Meta-Analysis.

Background: Physical exercise interventions are known to improve quality of life, motor and non-motor symptoms in people with Parkinson's disease (PD). However, systematic reviews and meta-analyses on cognitive outcomes are rare. Objective: To perform a systematic review and meta-analysis of physical exercise intervention effects compared with passive and active control groups (CGs) on global cognition in people with PD. Methods: A literature search was performed for randomized controlled trials (RCTs) on physical exercise interventions in PD using nine databases. We included RCTs reporting global cognition outcomes. A meta-analysis was performed using random-effects models and standardized mean differences (SMDs) with 95% confidence intervals (CIs). Bias was assessed with the revised Cochrane Risk of Bias tool and the certainty of evidence was rated using the GRADE approach. Results: Seventeen studies (ten with passive, seven with active CGs) were included in the systematic review. Exercise interventions varied considerably between studies. The meta-analysis included nine studies with 236 people with PD (seven with passive, two with active CGs). The SMD was 0.33 (95% CI 0.00; 0.65) demonstrating a small effect (p = 0.05) in favor of physical exercise. Compared with passive CGs, physical exercise had a small non-significant effect (SMD = 0.22, 95% CI -0.14;0.58, p = 0.24). Compared with active CGs, physical exercise had a medium significant effect (SMD = 0.72, 95% CI 0.12;1.33, p = 0.02). Conclusions: Physical exercise may increase global cognition in people with PD, but the evidence is very uncertain. Further large-scale RCTs are needed to confirm this finding and to identify the most effective type of physical exercise for improving cognition.