Obesity and extent of emphysema depicted at CT

Aim: To investigate the underlying relationship between obesity and the extent of emphysema depicted at CT. Methods and materials: A dataset of 477 CT examinations was retrospectively collected from a study of chronic obstructive pulmonary disease (COPD). The low attenuation areas (LAAs; ≤950 HU) of the lungs were identified. The extent of emphysema (denoted as %LAA) was defined as the percentage of LAA divided by the lung volume. The association between log-transformed %LAA and body mass index (BMI) adjusted for age, sex, the forced expiratory volume in one second as percent predicted value (FEV1% predicted), and smoking history (pack years) was assessed using multiple linear regression analysis. Results: After adjusting for age, gender, smoking history, and FEV1% predicted, BMI was negatively associated with severe emphysema in patients with COPD. Specifically, one unit increase in BMI is associated with a 0.93-fold change (95% CI: 0.91-0.96, p < 0.001) in %LAA; the estimated %LAA for males was 1.75 (95% CI: 1.36-2.26, p < 0.001) times that of females; per 10% increase in FEV1% predicated is associated with a 0.72-fold change (95% CI: 0.69-0.76, p < 0.001) in %LAA. Conclusion: Increasing obesity is negatively associated with severity of emphysema independent of gender, age, and smoking history.