Polymorphisms in the vitamin D receptor gene and type 1 diabetes mellitus risk: An update by meta-analysis

► This is the most comprehensive genetic meta-analysis on polymorphisms in VDR gene and T1DM risk. ► BsmI polymorphism is associated with increased T1DM risks, especially in Asians. ► FokI, ApaI and TaqI polymorphisms are not associated with T1DM risks. ► More studies with larger groups of patients and controls will be required. Four well known polymorphisms (BsmI, FokI, ApaI, TaqI) in the VDR gene have been implicated in susceptibility to type 1 diabetes mellitus (T1DM), but the results to date have been inconclusive. The aim of this study was to investigate the association between polymorphisms in the VDR gene and T1DM risk by meta-analysis. A total of 57 case–control studies in 26 published studies were included. The results indicated that the BsmI polymorphism is associated with increased risk of T1DM (BB+Bb vs. bb: OR=1.30, 95% CI=1.03–1.63), while the FokI, ApaI and TaqI polymorphisms were not. In the subgroup analysis by ethnicity, the increased risk of T1DM remained in the Asian subgroup for the BsmI polymorphism; whereas no significant association was found in other populations for other polymorphisms. Results from the current study suggest that the BsmI polymorphism is associated with increased risk of T1DM, especially in Asians. Further studies are needed to confirm our results.