The association of low bone mineral density with systemic inflammation in clinically stable COPD.

Chronic obstructive pulmonary disease (COPD) is known to be a systemic inflammatory disease which affects the function of many organs, and the low bone mineral density (BMD) may be the result of systemic inflammation. The aim of the present study was to explore the association of BMD with systemic inflammation in patients with clinically stable COPD. BMD and inflammatory markers, including C-reactive protein, tumor necrosis factor-alpha (TNF-α), and interleukin-6 (IL-6), were determined in all the recruited patients with clinically stable COPD. The patients were classified according to T scores, and the relationship between BMD with markers of systemic inflammation and that with other osteoporosis risk factors was assessed. There were no differences in age, female sex, body composition, tobacco exposure, and the use of respiratory medications among these groups. As the abnormality of BMD went severer, COPD patients with osteoporosis had significantly higher levels of systemic inflammation than those with either normal BMD or osteopenia. The presence of systemic inflammation was associated with a greater likelihood of low BMD, and multivariate logistic regression analysis showed that TNF-α and IL-6 were independent predictors of low BMD. It can be concluded that systemic inflammation is a significantly independent predictor of low BMD in patients with clinically stable COPD.