Association between vitamin D receptor gene polymorphisms and susceptibility to Parkinson's disease: a meta-analysis

Previous studies have reported an association between vitamin D receptor (VDR) gene polymorphisms and Parkinson's disease (PD), but the results were controversial. To explore whether VDR gene polymorphisms have an effect on PD risk, we performed this meta-analysis to evaluate the association between three VDR gene polymorphisms (Bsml, Apal, Taql) and PD susceptibility. We performed a systematic literature search for articles published up to February 2014 in multiple databases and selected seven eligible studies. Four studies were included for each polymorphism. Odds ratios (ORs) as well as their corresponding 95% confidence intervals (CIs) were used to estimate the association between VDR gene polymorphisms and PD risk in four phenotype models. Subgroup analysis and publication bias were also performed. Heterogeneity analysis and sensitivity analysis were performed if necessary. We failed to detect any association between Apal, Bsml, Taql polymorphisms and PD susceptibility in all four genetic models. In subgroup analysis grouped by ethnicity, no significant association was detected. The present meta-analysis indicates that the VDR genetic polymorphisms Bsml, Apal and Taql are not associated with susceptibility to PD. Because of the limited number of included studies, the results should be cautiously interpreted. More carefully designed studies are needed to verify our results.