Dissociation between Low Vitamin D Level and Hypertension in Coal Mine Workers: Evidence from the Kailuan Study

Objective The aim of this study was to evaluate the vitamin D status and the relationship between the vitamin D status and hypertension in a relatively large cohort in northern China. Methods This study was a part of the Kailuan study, consisting of 3,788 coal mine workers (including 2,532 underground workers and 1,256 surface workers) who received periodic health examinations between September 13, 2012 and December 24, 2012. Information on demographic factors, personal history and medical history were collected. The height, weight, blood pressure and serum25-hydroxyvitamin D [25(OH)D] level of each patient were measured. Results The mean 25(OH)D level in this cohort was 21.73±15.82 nmol/L. The number (%) of patients with vitamin D deficiency, insufficiency, inadequacy and sufficiency were 2,509 (66.24%), 1,051 (27.75%), 201 (5.31%) and 27 (0.71%), respectively. In all the participants, after adjusting for the age, salt intake, physical activity, smoking status, alcohol drinking status, work type, work environment, body mass index, diabetes and hyperlipidemia, the odds ratios for hypertension with 25(OH)D level ≥50, 25-50 and <25 nmol/L were 1.00 (reference), 1.44 (95%CI, 0.99-2.11) and 1.39 (95%CI, 0.97-1.99), respectively. Logistic regression models to evaluate the odds ratios and 95% CIs of hypertension for each quintile of the 25(OH)D level did not determine significant associations between the vitamin D status and hypertension. No significant associations were found in the underground workers or in the surface workers. Conclusion There was a high proportion of coal mine workers with vitamin D deficiency and insufficiency in Kailuan. However, no significant association between low vitamin D levels and hypertension was found in this cohort. Further investigations are needed to determine the relationship between vitamin D levels and hypertension.