Serum urate and the risk of Parkinson's disease: results from a meta-analysis.

OBJECTIVE Serum urate may exert protective effects against Parkinson's disease (PD) through its antioxidant capacities. In this article, we examine the hypothesis that high serum urate levels are associated with lower risk of PD. METHODS We searched NCBI (PubMed), ISI Web of Science and EMBASE for studies that reported the risk of PD associated with serum urate. Fixed or random effects meta-analysis was used to pool results across studies, and further analysis was used to assess the effects by gender. RESULTS Six studies met the inclusion criteria involving a total of 33 185 participants. Overall, we found a 33% reduction in PD incidence among persons with high serum urate level (relative risk [RR]=0.67; 95% confidence interval [CI], 0.50-0.91). Subgroup analysis was performed with 20 641 men and 12 544 women included, indicating statistically significant protective effects of serum urate in men (RR=0.60; 95% CI, 0.40-0.90) but not in women. A dose-response trend of serum urate to reduce PD risk was also observed involving 11 795 participants (RR=0.77; 95% CI, 0.68-0.88). Additionally, high serum urate levels seemed to slow the clinical decline of PD patients (RR=0.56; 95% CI, 0.43-0.72). CONCLUSIONS In light of these findings, our study confirms previous findings of a robust association between high serum urate level and PD risk, especially in men. It also suggests that long-term exposure to high serum urate may be linked to the delay of PD progression, however more well-designed investigations are needed.