Serum uric acid levels in patients with Parkinson’s disease: A meta-analysis

Lower serum uric acid (UA) levels have been reported as a risk factor in Parkinson's disease (PD). However, the results have been inconsistent so far.The aim of the present study was to clarify the potential relationship of uric acid with PD.Comprehensive electronic search in pubmed, web of science, and the Cochrane Library database to find original articles about the association between PD and serum uric acid levels published before Dec 2015. Literature quality assessment was performed with the Newcastle-Ottawa Scale. Random-effects model was used to estimate the standardized mean differences (SMDs) with 95% confidence intervals (CIs). Heterogeneity across studies was assessed using I2 and H2 statistics. Sensitivity analyses to assess the influence of individual studies on the pooled estimate. Publication bias was investigated using funnel plots and Egger's regression test. Analyses were performed by using Review Manager 5.3 and Stata 11.0.Thirteen studies with a total of 4646 participants (2379 PD patients and 2267 controls) were included in this meta-analysis. The current results showed that the serum UA levels in PD patients were significantly lower compared to sex and age-matched healthy controls (SMD: -0.49, 95% CI: [-0.67, -0.30], Z = 5.20, P < 0.001) and these results showed no geographic regional (Asia: SMD = -0.65, 95% CI [-0.84, -0.46], Z = 6.75, p <0.001; Non-Asia: SMD = -0.25, 95% CI [-0.43, -0.07], Z = 2.70, p = 0.007) and sex differences (women: SMD = -0.53, 95% CI [-0.70, -0.35], z = 5.98, p <0.001; men: SMD = -0.66, 95% CI [-0.87, -0.44], z = 6.03, p <0.001). Serum UA levels in middle-late stage PD patients with higher H&Y scales were significantly lower than early stage PD patients with lower H&Y scales (SMD = 0.63, 95% CI [0.36,0.89], z = 4.64, p <0.001).Our study showed that the serum UA levels are significantly lower in PD and the level is further decreased as the disease progresses. Thus it might be a potential biomarker to indicate the risk and progression of PD.