Abstract
Purpose: Although the explanation for inconsistencies in the reported association between serum 25-hydroxyvitamin D [25(OH)D] levels and chronic pain (CP) has not yet been determined, understanding this discrepancy is necessary for the development of vitamin D supplementation as an effective treatment for CP. The aim of this cross-sectional study was to examine the relationship between 25(OH)D concentrations and CP according to drinking habits in Japanese subjects. Patients and methods: We distributed invitation letters to 2314 individuals older than 40 years in Shika town, a rural area in Japan, and 724 subjects (386 females; mean age: 63.9 ± 10.4 years) were recruited. CP was defined as persistent pain lasting at least 3 months in any part of the body. Serum concentrations of 25(OH)D, a biomarker of the vitamin D status, were measured using a radioimmunoassay. A serum 25(OH)D level <20 ng/mL was defined as serum 25(OH)D deficiency. Drinking habits were assessed using a self-administered questionnaire. There were three choices, "rarely drink", "sometimes" and "everyday". Respondents who answered "rarely drink" were labelled as non-drinkers and the others as drinkers. Results: The prevalence of CP was 40.6%. A significant interaction between CP and drinking habits on 25(OH)D concentrations was observed (p = 0.098). A one-way analysis of covariance was performed to compare 25(OH)D concentrations between the subjects with and without CP in each drinking group, and the serum 25(OH)D levels of subjects with CP were significantly lower than those without CP among drinkers (p = 0.007). A logistic regression analysis revealed a correlation between serum 25(OH)D deficiency and CP in drinkers after adjustments for several confounding factors (odds ratio: 0.499; 95% confidence interval: 0.268 - 0.927; p = 0.028). Conclusion: The present results suggest that low serum 25(OH)D concentrations are associated with the development of CP in drinkers.