Association Between Serum 25-Hydroxyvitamin D Concentrations, CDX2 Polymorphism in Promoter Region of Vitamin D Receptor Gene, and Chronic Pain in Rural Japanese Residents

BACKGROUND: Previous studies examined the association between chronic pain (CP) and serum 25-hydroxyvitamin D (25(OH)D) concentrations; however, the findings obtained were inconsistent. Single nucleotide polymorphisms (SNP) associated with the transcriptional activity of the vitamin D receptor (VDR) gene may influence the association of 25(OH)D levels with CP. We aimed to clarify the association between CP, serum 25(OH)D concentration, and SNPs. METHODS: In the Shika study, we performed a cross-sectional analysis of 551 participants older than 40 years who were asked whether they had been having persistent pain lasting for at least 3 months in any part of the body on a self-administered questionnaire. Serum 25(OH)D concentrations were assessed as a biomarker of the vitamin D status using a radioimmunoassay. rs731236, rs7975232, rs1544410, rs2228570, and rs11568820 were identified using peripheral blood samples, and participants were assigned to those with or without the minor allele for each SNP. RESULTS: The prevalence of CP was 37.2%. We observed a tendency for lower 25(OH)D levels in participants with CP than in those without CP in the hetero/minor group of rs11568820, which is a polymorphism within the CDX2-binding site in the 1e promoter region of the VDR gene. Furthermore, a logistic regression analysis revealed that lower serum 25(OH)D concentrations were significantly associated with CP in the hetero/minor group, but not in the major group. CONCLUSION: These results suggest that sufficient serum 25(OH)D concentration reduces the risk of CP in individuals with the minor allele of the CDX2 polymorphism.