Association of Vitamin D Levels in Coal Miners: A Case-Control Study

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.

The present study estimated Vitamin D levels among underground coal miners in a tropical region and determined their associated factors.

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.

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.

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.