Clinical characterics of cases and controls
| Controls | Cases | p value | |
| Subjects | 280 | 441 | |
| Age years | 59 (15) | 65 (9) | <0.001# |
| Sex male % | 64 | 68 | 0.23 |
| Smoking history pack-years | 22 (19)+ | 41 (18) | <0.001# |
| BMI kg·m−2 | 27.9 (5.7) | 27.8 (6.1) | 0.57 |
| BODE index | 0 | 1 (2) | <0.001# |
| FEV1/FVC LLN % | 0 | 78 | <0.001# |
| 6MWD m | 545 (136) | 468 (124) | <0.001# |
| Dyspnoea score | 0 (0) | 1 (1) | <0.001# |
| Spirometry | |||
| FEV1 L | 3.2 (1.0) | 1.9 (0.8) | <0.001# |
| FEV1 % predicted | 109 (19) | 71 (27) | <0.001# |
| FEV1/FVC % | 78.8 (6.6) | 56.8 (15.8) | <0.001# |
| Bronchodilator reversibility L | 0.11 (0.16) | 0.13 (0.17) | <0.001# |
| Lung mechanics | |||
| Raw kPa·s·L−1 | 0.18 (0.11) | 0.3 (0.21) | <0.001# |
| sRaw kPa·s | 0.7 (0.38) | 1.4 (1.1) | <0.001# |
| Rin kPa·s·L−1 | 0.15 (0.09) | 0.23 (0.14) | <0.001# |
| Rex kPa·s·L−1 | 0.2 (0.14) | 0.36 (0.32) | <0.001# |
| Lung volumes | |||
| TLC L | 6.5 (1.8) | 7.1 (2.0) | <0.001# |
| TLC % predicted | 107 (19) | 115 (24) | <0.001# |
| RV L | 2.4 (0.8) | 3.4 (1.3) | <0.001# |
| RV % predicted | 106 (30) | 150 (55) | <0.001# |
| RV/TLC % predicted | 0.95 | 1.23 | <0.001# |
| Gas exchange | |||
| PO2 mmHg | 78.8 (12.05) | 70.9 (10.4) | <0.001# |
| PCO2 mmHg | 38.49±3.67 | 38.0±3.7 | 0.087 |
| PA–aO2 mmHg | 22.88 (13.0) | 31.1 (12.3) | <0.001# |
| TLCO/VA % predicted | 100 (21) | 79 (33) | <0.001# |
| Blood parameters | |||
| Leukocytes 109 cells·L−1 | 6.3 (2.0) | 7.1 (2.4) | <0.001# |
| Lymphocytes 109 cells·L−1 | 1.8 (0.7) | 1.9 (0.8) | 0.47 |
| Neutrophils 109 cells·L−1 | 3.8 (1.7) | 4.3 (2.0) | <0.001# |
| Eosinophils 109 cells·L−1 | 0.12 (0.12) | 0.16 (0.16) | <0.001# |
| Haemoglobin mg·dL−1 | 14.3±1.2 | 14.5±1.2 | <0.001# |
| Haematocrit % | 42 (4) | 43 (5) | <0.001# |
| Erythropoetin mIU·mL−1 | 8.8 (6.5) | 11.5 (8.4) | <0.001# |
| IgE kU·L−1 | 33 (75) | 11 (8) | <0.001# |
| CRP mg·dL−1 | 0.3 (0.4) | 0.4 (0.3) | <0.001# |
| AAT mg·dL−1 | 123 (21) | 130 (30) | <0.001# |
| CT parameters | |||
| WA/BSA mm2·m−2 | 15.6 (7.2) | 15.4 (6.3) | 0.94 |
| LA/BSA mm2·m−2 | 7.9 (3.7) | 7.9 (5.5) | 0.81 |
| WA % | 61.2 (10.8) | 64.0 (9.7) | <0.001# |
| Lung density Perc15 HU | −907 (17.4) | −919 (26) | <0.001# |
| Emphysema distribution | −1.7 (20.2) | −3.3 (30.2) | 0.48 |
Data are presented as median (interquartile range) or mean±sd, unless otherwise stated. BMI: body mass index; BODE: body-mass index, airflow obstruction, dyspnoea, exercise; FEV1: forced expiratory volume in 1 s; FVC: forced vital capacity; LLN: lower limit of normal; 6MWD: 6-min walk distance; Raw: airway resistance; sRaw: specific airway resistance; Rin: inspiratory resistance; Rex: expiratory resistance; RV: residual volume; TLC: total lung capacity; PO2: oxygen tension; PCO2: carbon dioxide tension; PA–aO2: alveolar–arterial oxygen tension differential; TLCO: transfer capacity of the lung for carbon monoxide; VA: alveolar volume; Ig: immunoglobulin; CRP: C-reactive protein; AAT: α1-antitrypsin; CT: computed tomography; WA/BSA: airway wall area corrected for body surface area; LA/BSA: lumen area corrected for body surface area; WA: airway wall area; Perc15: 15th percentile point. #: significant after correction for multiple testing; +: 47 out of 280 were never-smokers.