Baseline characteristics of subjects (mean values)
| Characteristic | Smoking status at baseline | Statistic (p value) | |
| Current (n=548) | Former (n=178) | ||
| Gender, male/female (n) | 295/253 | 98/80 | 0.843 |
| Age, years (range) | 58.0 (49–71) | 58.2 (50–69) | 0.623 |
| Pack-years (SD) | 36 (12) | 35 (12) | 0.362 |
| BMI (SD) | 24.9 (3.9) | 26.2 (3.6) | <0.001 |
| FEV1 (SD) | 2.8 (0.7) | 3.0 (0.8) | 0.014 |
| Predicted % FEV1 (SD) | 92% (17) | 96% (17) | 0.004 |
| FEV1/FVC (SD) | 70% (7.5) | 72% (7.3) | 0.001 |
The χ2 test was applied to obtain the p value for gender, while Student's t test was used for the rest.
BMI, body mass index; FEV1, forced expiratory volume in the first second; FVC, forced vital capacity.