Association Between Collagen Ix Tryptophan Polymorphisms And Risk Of Lumbar Disc Degeneration: A Meta-Analysis

Purpose: The aim of this study was to examine the association between collagen IX tryptophan (COL9A2/Trp2, COL9A3/Trp3) polymorphisms and risk of lumbar disc degeneration (LDD). Methods: Data were collected from several electronic bibliographical databases, including PubMed, EMBASE, the Cochrane Library, and Web of Science, with the most recent report published on June 20, 2018. Odds ratios (OR) and 95% confidence intervals (CI) were used to assess the strength of association between collagen IX tryptophan (COL9A2/Trp2, COL9A3/Trp3) polymorphisms and LDD risk. Statistical analysis was performed using STATA 12.0 software. Results: A total of 1,509 LDD cases and 1646 controls from 9 studies were included, comprising Asian and Caucasian populations. For the determination of associations of collagen IX Trp2 allele and Trp3 allele polymorphisms, six and eight studies, respectively, were included in the final meta-analysis. There was no evidence that Trp2 polymorphism in COL9A2 had a significant association with LDD risk. However, Trp3 polymorphism had a significant association with LDD risk (allele model: OR=2.11, 95% CI=1.52-2.93, P<0.001; dominant model: OR=2.13, 95% CI=1.51-3.01, P<0.001; heterozygote model: OR=2.31, 95% CI=1.44-2.89, P<0.001; additive model: OR=0.50, 95% CI=0.35-0.70, P<0.001). Subgroup analysis, stratified by Caucasian populations, confirmed the above results. Furthermore, no significant publication bias was observed in this study. Conclusion: Overall, this meta-analysis suggests that the Trp3 allele polymorphism in COL9A3 may be associated with an increased risk of LDD. However, the Trp2 allele polymorphism is nota major risk factor for LDD. Further studies with a larger and more homogeneous sampling of individuals with LDD are required to confirm these results.