Analysis of factors associated with the lumbar spine and proximal femur bone mineral density in coal miners: a cross-sectional survey. (December 2017) - Kuang, Sijie
Abstract: Background: Chinese coal miners are at high risk of occupational disease becausethey work underground during most of the daylight hours and are exposed to weight-bearing activity. But data concerning bone mineral density (BMD) and risk factors of BMD is lacking. We aim to identify the factors associated with low bone BMD in coal miners. Methods: Measurements were taken at the lumbar spine and proximal femur using DXA (OSTEOCORE-2 Vision, Medilink, France). Demographic, lifestyle, physical, and occupational characteristics were collected through standardised questionnaires. Univariate, multivariate, and multiple regression were performed. Findings: We recruited 1650 coal miners aged 30–60 years from Kailuan, a city in Hebei province of China, from May to November, 2011. 51 miners (10%) older than 50 years were osteoporotic, and 191 miners (36%) had osteopenia at the lumbar spine. Four miners (1%) were osteoporotic, and 134 miners (25%) had osteopenia at the femoral neck. Pearson correlation showed that lumbar spine and femoral neck BMD correlated positively with weight (r=0·155, p<0·0001; r=0·194, p<0·0001) and body-mass index (BMI; r=0·108, p<0·0001; r=0·177, p<0·0001). Number of years of work (r=–0·134, p<0·0001) and age (r=–0·116, p<0·0001) were negatively correlated with femoral neck BMD. On multiple regression analysis, BMI was the only independent predictor of lumbar spine BMD (η 2 =0·005, p<0·0001), whereas both BMI (η 2 =0·007, p<0·0001) and years of work (η 2 =0·003, p<0·01) were independent predictors of femoral neck BMD. Interpretation: Age, low BMI, and long duration of work are risk factors for low BMD of coal miners in China, along with low calcium supplements intake, less time of sun exposure, smoking, and drinking history. Funding: Specific Research Project of Health Pro bono Sectors, Ministry of Health, China (201002014).