Clinical characteristics of subjects
| Variables | Groningen | LAVAL | UBC | |||
| Never-smokers | Current smokers | Never-smokers | Current smokers | Never-smokers | Current smokers | |
| Subjects | 12 | 45 | 27 | 82 | 17 | 88 |
| Male/female | 5 (42%)/7 | 23 (51%)/22 | 6 (22%)/21 | 37 (45%)/45 | 8 (47%)/9 | 54 (61%)/34 |
| Age years | 48.3±15.4 | 57.5±8.7 | 55.8±11.6 | 63±9.2 | 59.6±14.6 | 62±9.4 |
| Smoking pack-years | 0 | 37.9±17.4 | 0 | 53±21.8 | 0 | 53.7±27.1 |
| FEV1 % pred | 98.6±9.38 (7) | 73.3±19.8 (17) | 94.1±13.2 (4) | 75.1±14.4 (1) | 105.4±33.1 (7) | 76.4±18.2 (7) |
| FVC % pred | 98.8±7.3 (7) | 87.1±16.3 (18) | 96.5±12.5 (6) | 87. 1±13.5 (5) | 99.1±31.2 (6) | 86.7±15.7 (7) |
Data are presented as mean±sd, unless otherwise stated. The number of missing values is shown in parentheses. LAVAL: Laval University; UBC: University of British Columbia; FEV1: forced expiratory volume in 1 s; FVC: forced vital capacity.