| Characteristic | No COPD | Mild COPD | Severe COPD |
| Patients | 7 | 6 | 13 |
| GOLD stage | I and II | III and IV | |
| Age yrs | 63.3±7.1 | 69.8±3.6 | 56.2±2.1* |
| Sex male/female | 1/6 | 5/1 | 5/8 |
| FEV1 % pred | 115.9±8.5 | 79.7±3.3 | 21.1±2.3 |
| Smoking pack-yrs | 0 | 35±6.8 | 61.3±9.0 |
| Current smoker | 0 | 1 | 0 |
| Medication | |||
| Oral corticosteroid | 0 | 2 | 1 |
| Inhaled corticosteroid | 0 | 0 | 5 |
| Accompanied with lung cancer | 4 | 5 | 1 |
Data are presented as n or mean±se, unless otherwise stated. COPD: chronic obstructive pulmonary disease; GOLD: Global Initiative for Chronic Obstructive Lung Disease; FEV1: forced expiratory volume in 1 s; % pred: % predicted.*: p<0.05 versus mild COPD.