Demographic characteristics and lung function measurements in this study
| Controls | Cases | p-value# | |
| Subjects n | 248 | 244 | |
| Age yrs | 54.9±10.2 | 58.4±8.2 | <0.001 |
| Males % | 51.6 | 59.0 | 0.10 |
| Current smoker % | 57.3 | 48.8 | 0.07 |
| Pack-yrs of smoking | 19.1±13.4 | 28.8±15.1 | <0.001 |
| FEV1 L | 3.30±0.75 | 1.69±0.75 | <0.001 |
| FVC L | 4.15±0.93 | 3.16±1.03 | <0.001 |
| FEV1 % pred | 95.4±10.0 | 50.0±18.4 | <0.001 |
| FVC % pred | 97.9±10.1 | 76.0±17.1 | <0.001 |
| FEV1/FVC ratio | 0.80±0.04 | 0.52±0.13 | <0.001 |
Data are presented as mean±sd, unless otherwise stated. FEV1: forced expiratory volume in one second; FVC: forced expiratory volume; % pred: per cent predicted. #: difference between cases and controls.