Association between high uric acid and the risk of Parkinson's disease: A meta-analysis.

BACKGROUND: Uric acid, as an important antioxidant substance in human body, has attracted much attention in relation to the risk of Parkinson's disease (PD). However, the causal relationship between them is still controversial. We perform a meta-analysis to summarize the available evidence from cohort studies on the association between high uric acid and the risk of PD. METHODS: We searched the Cochrane Library, PubMed, Medline, and Embase to obtain the Odds Ratio (OR) of high uric acid and PD and pooled the data using RevMan software (v5.4; Cochrane library). RESULTS: A total of 18 studies involving more than 840,774 participants were included. Overall, we found a significant association (OR = 0.84; 95% CI: 0.77-0.91) between high uric acid and PD. Subgroup analysis was stratified by gender, indicating more statistically significant protective effects of serum urate in men (OR = 0.66; 95% CI: 0.54-0.81) than that of in women (OR = 0.86; 95% CI: 0.76-0.98). People under the age of 60 (OR = 0.53, 95% CI: 0.33-0.86) are more likely to benefit from high uric acid than people over age of 60 (OR = 0.73, 95% CI: 0.63-0.86). The resistance of high uric acid to PD in LRRK2 mutation carriers (OR = 0.22, 95% CI: 0.11-0.45) is stronger than that in non-manifesting LRRK2 mutation carriers (OR = 0.37, 95% CI: 0.16-0.85). In addition, a dose-response trend of serum urate to reduce PD risk was also observed (OR = 0.68; 95% CI: 0.48-0.93). CONCLUSION: Our study confirms a significant association between high uric acid and the risk of PD, especially in men under 60 years old, and a dose-response trend of uric acid to reduce PD risk was also observed. Furthermore, LRRK2 mutation carriers are more likely to benefit from high uric acid than non-manifesting LRRK2 mutation carriers.

Asymmetric transmission of elastic shear vertical waves in solids.

In this work, we propose an asymmetric transmission structure (ATS) for elastic shear vertical (SV) waves in solids, which has been relatively unexplored. The ATS is constituted by a metasurface and a phononic crystal (PC) possessing a directional band gap. While the metasurface aims to redirect the incident wave, the PC acts as a directional filter. The metasurface is composed of a stacked array of composite plates with two connecting parts made of different materials. To examine the performance of the designed ATS, full numerical simulations have been conducted. The numerical results indicate that the proposed ATS offered a relatively broad working frequency band and had a one order of magnitude difference in terms of transmission between the positive and negative incidences. Our study provides an alternative method to control elastic SV waves and could benefit applications in various fields, such as Micro-Electro-Mechanical System (MEMS), in which thin plates are frequently used components.