Osteoporosis prevalence and associated factors in patients with COPD: a cross-sectional study.

BACKGROUND Osteoporosis is one of the systemic features of COPD. OBJECTIVE To determine the prevalence of osteoporosis in a sample of COPD out-patients, and investigate the correlation between T-score (a comparison of the patient's bone mineral density to that of a healthy 30-year-old of the same sex and ethnicity) and several factors suggested to be associated with osteoporosis. METHODS In a cross-sectional study, we conducted dual-energy X-ray absorptiometry bone mineral density scans of the hips and lumbar spine, and collected data on smoking and alcohol habits, menopausal status, comorbidities, inhaled and oral corticosteroid dose and duration of treatment, previous bone fractures, pulmonary function tests, calcium intake (via questionnaire on food frequency), vitamin D intake (via questionnaire on sunlight exposure), and physical activity (via the International Physical Activity Questionnaire). RESULTS We evaluated 95 patients. Forty (42%) were osteoporotic, 40 (42%) were osteopenic, and 15 (16%) had normal bone mass. We found significant bivariate correlations between femoral-neck T-score and body mass index (r = 0.551, P < .001), and femoral-neck T-score and International Physical Activity Questionnaire total activity score (r = 0.378, P < .001). There was a significant inverse relationship between femoral-neck T-score and BODE (body mass index, air-flow obstruction, dyspnea, and exercise capacity) index (r = -0.246, P = .02). We also found significant correlations between T-score and FEV(1) (r = 0.251, P = .01), forced vital capacity (r = 0.229, P = .03), percent-of-predicted functional residual capacity (r = -0.415, P < .001), inspiratory capacity (r = 0.252, P = .01), ratio of inspiratory capacity to total lung capacity (r = 0.241, P = .02), and absolute and percent-of-predicted diffusing capacity of the lung for carbon monoxide (r = 0.366, P < .001, and r = 0.338, P = .003, respectively). CONCLUSIONS We identified a high prevalence of osteoporosis and osteopenia in out-patients with COPD. Patients with osteoporosis had more severe COPD than patients with normal bone mass.