Background: Chronic obstructive pulmonary disease (COPD) is characterized by the presence of airflow limitation due to loss of lung elasticity and/or airway narrowing. The pathological hallmark of loss of lung elasticity is emphysema and airway wall remodeling contributes to the airway narrowing. Using computed tomography (CT) these lesions can be assessed by measuring low attenuation areas (LAA) and airway wall thickness/luminal area, respectively. We have reported that COPD can be divided into airway dominant, emphysema dominant and mixed phenotypes using CT. In this study we postulated that the patients' physique may be associated with the relative contribution of these lesions to airflow obstruction.
Methods: We used CT to evaluate emphysema and airway dimensions in 201 COPD patients. Emphysema was evaluated using the percentage of LAA voxels (LAA%) and the airway lesion was estimated by the percentage wall area (WA%). We divided patients into four phenotypes using LAA% and WA%.
Results: Body mass index (BMI) was significantly lower in the higher LAA% phenotype, i.e. emphysema dominant and mixed phenotypes. BMI correlated with LAA% (ρ=-0.557, p<0.0001) but not with WA%. BMI was significantly lower in the emphysema dominant phenotype than in the airway dominant phenotype, while there was no difference in FEV1 %predicted between the two.
Conclusion: A low BMI is associated with the presence of emphysema, but not with airway wall thickening in male smokers who have COPD. These results support the concept of different COPD phenotypes and suggest that there may be different systemic manifestations of these phenotypes.
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