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Chronic obstructive pulmonary disease (COPD) is characterised by the presence of airflow limitation caused by loss of lung elastic recoil and/or airway narrowing. 1 Emphysema is the pathological lesion that correlates most closely with loss of lung elastic recoil, 2 while the airway component is characterised by thickening and narrowing of membranous bronchioles. 3 We have previously reported that the relative contributions of these processes to airflow obstruction in individual patients with COPD can be assessed by measuring low attenuation area (LAA) and airway wall thickness/luminal area using CT. 4 5 Dividing patients with COPD into airway dominant, emphysema dominant and mixed phenotypes may aid in the study of the pathogenesis, in the assessment of pharmacological interventions and ultimately in the choice of patient specific therapy. 6
There is increasing evidence that COPD is a systemic illness 7 8 and low body weight is a prominent systemic manifestation. The cachexia associated with COPD was traditionally believed to be more prevalent among those whose airflow limitation was due to predominant emphysema and those who had a relatively maintained ventilatory drive (the "pink puffer" hypothesis). 9 The ability to make quantitative estimates of the degree of emphysema in individual patients allows a test of the longstanding hypothesis that emphysema predominant patients with COPD have a lower lean body mass.
We hypothesised that COPD phenotypes are associated with different patient physiques. In this study, we recruited 238 smokers and patients with COPD and divided them into four groups based on measurements of emphysema and airway dimensions using CT. Body mass index (BMI kg/m 2 ) was compared among the groups and the relationships between BMI and CT parameters were examined.
METHODS
Subjects
This is part of an ongoing COPD follow-up study in Kyoto University. A total of 239 smokers (219 patients with COPD from Kyoto University Hospital and 20 asymptomatic volunteers) were recruited. Results from a subset of these patients have been reported previously, 4 6 but the objectives of the present analyses are distinct from those addressed in the previous study. All asymptomatic volunteers were male, and there were 201 men and 18 women with COPD. Because we did not have enough women who had COPD to determine the influence of BMI in each gender, we excluded...