[Effect of underground work on cardiovascular system 
in coal miners]

To study the effect of underground work on cardiovascular system health in coal miners.

Male coal miners, who received electrocardiographic examinations between June, 2013 and August, 2014 in Hunan Prevention and Treatment Institute for Occupational Diseases to exclude pneumoconiosis, were enrolled for this study (n=3 134). Miners with 2 years or more underground work experience were selected as the exposed group (n=2 370), while miners without underground work experience were selected as the control group (n=764). The prevalence of electrocardiographic abnormalities and the influential factors were compared between the 2 groups.

The prevalences of electrocardiographic abnormalities, hypertension, heart rate abnormalities and cardiovascular system abnormalities in the exposed group vs the control group were 37.6% vs 25.4%, 20.5% vs 13.4%, 5.7% vs 6.0%, 49.8% vs 35.2%, respectively. The cardiovascular system abnormalities were correlated with the underground work (OR=3.128, 95% CI: 1.969-4.970), the underground work experience (OR=1.205, 95% CI: 1.070-1.358) and the type of works (mining worker OR=1.820, 95% CI: 1.527-2.169; auxiliary worker OR=1.937, 95% CI: 1.511-2.482; other worker OR=3.291, 95%CI: 2.120-5.109).

Underground work may increase the prevalence of cardiovascular system abnormalities for coal miners. The longer the coal miners work in underground, the higher the risk of the cardiovascular system abnormalities they are.