Exploring the Association Between Emphysema Phenotypes and Low Bone Mineral Density in Smokers with and without COPD

Rationale Emphysema and osteoporosis are tobacco-related diseases. Many studies have shown that emphysema is a strong and independent predictor of low bone mineral density (BMD) in smokers; however, none of them explored its association with different emphysema subtypes. Objective To explore the association between the different emphysema subtypes and the presence of low bone mineral density in a population of active or former smokers with and without chronic obstructive pulmonary disease (COPD). Methods One hundred and fifty-three active and former smokers from a pulmonary clinic completed clinical questionnaires, pulmonary function tests, a low-dose chest computed tomography (LDCT) and a dual-energy absorptiometry (DXA) scans. Subjects were classified as having normal BMD or low BMD (osteopenia or osteoporosis). Emphysema was classified visually for its subtype and severity. Logistic regression analysis explored the relationship between the different emphysema subtypes and the presence of low BMD adjusting for other important factors. Results Seventy-five percent of the patients had low BMD (78 had osteopenia and 37 had osteoporosis). Emphysema was more frequent (66.1 vs 26.3%, p=<0.001) and severe in those with low BMD. Multivariable analysis adjusting for other significant cofactors (age, sex, FEV1, and severity of emphysema) showed that BMI (OR=0.91, 95% CI: 0.76-0.92) and centrilobular emphysema (OR=26.19, 95% CI: 1.71 to 399.44) were associated with low BMD. Conclusion Low BMD is highly prevalent in current and former smokers. BMI and centrilobular emphysema are strong and independent predictors of its presence, which suggests that they should be considered when evaluating smokers at risk for low BMD.