Association between vitamin D receptor gene polymorphisms and intervertebral disc degeneration: A meta-analysis

Background: Studies that have investigated the association between vitamin D receptor (VDR) gene polymorphisms and intervertebral disc degeneration (IDD) have yielded inconsistent results. Methods: To investigate the association between VDR gene polymorphisms and IDD, a systematic literature search for relevant published studies was performed on PubMed, Embase, Web of Science, Cochrane library, Wan-Fang, and CNKI databases. A random effects model was used for heterogeneous data; while a fixed effect model was used for homogenous data. Odds ratios (OR) and 95% confidence intervals (CI) were calculated to evaluate the strength of the association. Results: We observed no association between VDR FokI, TaqI-ApaI polymorphisms and IDD. However, on subgroup analysis by ethnicity, VDR FokI mutation was associated with a significantly lower risk for IDD [dominant model: OR = 0.78, 95% CI = 0.65-0.93; heterozygote model: OR = 0.76, 95% CI = 0.63-0.92; allele model: OR = 0.86, 95% CI = 0.75-0.98] among Caucasians. Conclusion: These results suggest that the VDR FokI polymorphism may be associated with IDD among Caucasians. However, the association between VDR TaqI-ApaI polymorphisms and IDD in Asians is still not clear. Further well-designed studies are needed to arrive at a definitive conclusion. (C) 2016 The Japanese Orthopaedic Association. Published by Elsevier B.V. All rights reserved.