Pulmonary function, exposure time and smoking habits in the three groups, identified on the basis of standard chest radiograph
| Group 1 | Group 2 | Group 3 | p‐value | |
| FVC % | 90.6±9.1 | 83.5±10.4 | 64.0±6.2 | <0.001 |
| FEV1 % | 94.6±15.4 | 77.8±9.1 | 68.7±4.2 | 0.004 |
| FEF25–75 % | 111.1±30.7 | 80.0±5.5 | 74.0±4.0 | 0.014 |
| Exposure yrs | 15.0±7.4 | 31.2±3.0 | 31.3±3.5 | <0.001 |
| Cigarettes day | 10.9±11.2 | 12.2±12.4 | 2.7±3.1 | NS |
Data are presented as mean±sd unless otherwise stated
FVC: forced vital capacity
FEV1: forced expiratory volume in one second
FEF25–75: forced mid-expiratory flow
NS: nonsignificant