Risk factors for osteoporosis in Caucasian patients with moderate chronic obstructive pulmonary disease: A case control study

The prevalence of osteoporosis is high in chronic obstructive pulmonary disease (COPD) patients. The gold standard for the diagnosis of osteoporosis is bone mineral density (BMD) measurements as assessed by dual energy absorptiometry (DXA) scanning as well as vertebral fractures as assessed by instant vertebral assessment (IVA). The aim of this study was to compare COPD GOLD II patients (that is, patients with moderate COPD, stage II, according to the GOLD classification) with osteoporosis (cases) to COPD GOLD II patients without osteoporosis (controls) to identify risk factors for osteoporosis. The diagnosis of osteoporosis was based on BMD and vertebral fractures. Cases (n=49) were matched for gender, age and forced expiratory volume in the first second to controls (n=49). We assessed pulmonary function, body composition, vitamin D, emphysema score (by high-resolution computer tomography), medical history and medication use in all patients. Variables that were significantly different between the cases and controls were included in a logistic regression analysis. COPD patients with osteoporosis had a significantly lower body mass index (BMI) and higher residual volume as the percentage of total lung capacity (RV%TLC) compared to COPD patients without osteoporosis. Decreasing BMI and increasing RV%TLC increased the odds ratio for osteoporosis. Overweight and obese BMI values were protective for osteoporosis. Screening for osteoporosis should be performed even in moderate COPD patients, especially in those with a low BMI and/or a high RV%TLC.