Reduced Bone Density and Vertebral Fractures in Smokers: Men and COPD Patients at Increased Risk

Rationale: Former smoking history and Chronic Obstructive Pulmonary Disease (COPD) are potential risk factors for osteoporosis and fractures. Under existing guidelines for osteoporosis screening, women are included but men are not, and only current smoking is considered. Objectives: To demonstrate the impact of COPD and smoking history on the risk of osteoporosis and vertebral fracture in men and women. Measurements: Volumetric bone mineral density (vBMD) by calibrated quantitative CT (QCT), visually scored vertebral fractures and severity of lung disease were determined from chest CT scans of 3321 current and ex-smokers in COPDGene study. Low volumetric bone mineral density as a surrogate for osteoporosis was calculated from young adult normal values. Methods: Characteristics of participants with low volumetric bone mineral density were identified and associated to COPD and other risk factors. We tested associations of gender and COPD to both volumetric bone mineral density and fractures adjusting for age, race, BMI, smoking and glucocorticoid use. Main Results: Male smokers had a small but significantly greater risk of low volumetric bone mineral density (- 2.5 SD below young adult mean by calibrated quantitative CT) and more fractures than female smokers. Low volumetric bone mineral density was present in 58% of all subjects, was more frequent with worse COPD and rose to 84% of very severe COPD subjects. Vertebral fractures were present in 37% of all subjects and were associated with lower volumetric bone mineral density at each GOLD stage. Vertebral fractures were most common in the mid-thoracic region. COPD and specifically emphysema were associated with both low volumetric bone mineral density and vertebral fractures after adjustment for steroid use, age, pack years, current smoking and exacerbations. Airway disease was associated with higher bone density after adjustment for other variables. Calibrated quantitative CT identified more abnormal subjects than the standard DXA in a subset of subjects and correlated well with prevalent fractures. Conclusion: Male smokers with and without COPD, have a significant risk of low bone mineral density and vertebral fractures. COPD was associated with low volumetric bone mineral density after adjusting for race, gender, BMI, smoking, steroid use, exacerbations and increasing age. Screening for low bone mineral density in men and women smokers using quantitative CT scanning will increase opportunities to identify and treat osteoporosis in this at-risk population.