Reference sample selection criteria and characteristics of the study sample
| Males | Females | |
| Participants (White) interviewed n | ||
| Total | 13883 | 16646 |
| Less invalid spirometry data | 11854 | 13554 |
| Less ever smokers | 4643 | 6845 |
| Less nonhealthy subjects | 3107 | 4195 |
| Less irreproducible data | 2497 | 3556 |
| Age in years n | ||
| 16–24 | 424 | 507 |
| 25–34 | 620 | 802 |
| 35–44 | 583 | 750 |
| 45–54 | 376 | 593 |
| 55–64 | 260 | 416 |
| 65–74 | 157 | 329 |
| 75–84 | 51 | 134 |
| ≥85 | 8 | 25 |
| Age last birthday yrs | 40±15.7 | 43±17.0 |
| Height cm | 176±6.8 | 162±6.4 |
| FEV1 L | 4.1±0.81 | 2.9±0.65 |
| FVC L | 5.0±0.94 | 3.5±0.74 |
| FEV1/FVC | 0.82±0.072 | 0.83±0.071 |
Data are presented as absolute values or mean±sem
FEV1: forced expiratory volume in one second
FVC: forced vital capacity