Association Between Serum Zinc Levels and the Risk of Parkinson's Disease: a Meta-Analysis.

Recent studies have found that the serum zinc levels were associated with the risk of Parkinson's disease (PD), but the results were inconsistent. Thus, we conducted a meta-analysis to summarize the evidence from observational studies between them. Pertinent studies were identified by a search in PubMed, Embase, and Web of science up to July, 10, 2016. Standardized mean difference (SMD) and 95% confidence intervals (CI) with random-effect model was used to combine the results. Subgroup analysis and meta-regression were also conducted. Publication bias was estimated using Begg's regression asymmetry test. A total of 11 articles involving 822 PD patients and 777 healthy controls were included in the meta-analysis. Our meta-analysis results revealed that the serum zinc levels in PD patients were significantly lower than those in health controls (SMD = -0.779, 95%CI = [-1.323, -0.234], P < 0.001). The association was also significant oriental studies (SMD = -1.601, 95%CI = [-2.398, -0.805], P < 0.001). No publication bias was found. The current study indicated that serum zinc levels in PD patients were significantly lower than those in healthy controls.