Meta-analysis of the association between serum iron levels and Parkinson's disease: Evidence from 11 publications

Background: There is no consensus on the serum iron levels and Parkinson's disease (PD). The aim of this study is to conduct a systematic review and meta-analysis to analyse the relationship between serum iron levels and PD risk. Methods: We searched the databases of PubMed, Web of knowledge, Embase, the Cochrane Library, China National Knowledge Infrastructure (CNKI) and China Biology Medical literature to assess the association between serum iron levels and PD risk. Standardized mean differences (SMD) and 95% confidence intervals (CI) with random-effect model were used to combine the results. Results: Eleven related articles met our selection criteria and contained a total of 829PD patients and 1219 healthy controls. Our meta-analysis results revealed that the serum iron levels in PD patients were significantly higher than those in healthy controls (SMD=0.27, 95% CI=0.18, 0.37, P < 0.001). Subgroup analysis by ethnicity showed that the serum iron levels in PD patients were significantly higher than controls both in Asian populations and European populations. Significant associations were also found in prospective studies and case-control studies. Conclusions: Our meta-analysis showed strong evidence that a significantly higher serum iron levels are present in PD patients when compared to the healthy controls. (C) 2016 Elsevier B.V. All rights reserved.