Association of vitamin D levels in coal miners: A case-control study

Introduction: Coal miners working underground are likely to be at greater risk of developing Vitamin D deficiency due to reduced sunlight exposure. To date, only three studies have been reported, with no significant risk of Vitamin D deficiency among coal miners. None were conducted in the tropical region, where sunlight is ample. Objective: The present study estimated Vitamin D levels among underground coal miners in a tropical region and determined their associated factors. Methods: Serum calcium, 25-hydroxyvitamin D, and bone turnover markers among underground and surface workers were estimated in a matched case-control study. Binary logistic regression analysis was performed using case/control as the dependent variable to estimate odds ratios and 95% confidence intervals of variables which significantly (P < 0.1) differed among the cases and controls. Results: The mean Vitamin D level among both coal miners (22.12 ng/dl) and surface workers (23 ng/dl) were low. No significant difference was noted for all biochemical parameters after adjusting for other covariates except the parathyroid hormone (PTH), which was marginally higher among the surface workers. Conclusions: Even in the absence of statistically significant evidence of low Vitamin D level in underground workers compared to surface workers, there was indirect evidence (of differences in PTH) to indicate that Vitamin D level is lower in underground workers probably because of poor sunlight exposure.