Characteristics of study samples
| AAT | EOCOPD | ICGN | Norway | |
| No of subjects | 372 | 972 | 3058 | 1909 |
| Mean (SD) age (years) | 52 (10) | 46 (18) | 58 (8) | 61 (11) |
| Female, n (%) | 202 (54) | 567 (58) | 1374 (45) | 847 (44) |
| Ever smokers, n (%) | 231 (62) | 659 (68) | 3058 (100) | 1909 (100) |
| Median (IQR) pack-years of smoking | 5 (0–19) | 14 (0–35) | 39 (25–55) | 23 (13–34) |
| Median (IQR) FEV1 (% predicted) | 58 (33–93) | 84 (60–96) | 58 (35–87) | 76 (48–90) |
AAT, Alpha-1 Antitrypsin Genetic Modifiers Study; EOCOPD, Boston Early-Onset COPD Study; FEV1, forced e xpiratory volume in 1 s; ICGN, International COPD Genetics Network; Norway, the Bergen, Norway Case–Control Study.