Characteristics and spirometry values of participants in the healthy subgroup, stratified by sex and by survey
| BCRDS | PSWON | HCRHS | BD-HUSK | Total | |
| Survey years | 1965–1970 | 1988–1990 | 1996–1997 | 1998–1999 | 1965–1999 |
| Birth years | 1894–1943 | 1944–1958 | 1914–1969 | 1925–1951# | 1894–1969 |
| Number of subjects¶ | 1438 (26) | 5674 (22) | 409 (21) | 521 (19) | 8042 (22) |
| Males | |||||
| Subjects | 328 (23) | 5674 (100) | 154 (38) | 136 (26) | 6292 (78) |
| Age years | 40.8±14.4 | 37.8±4.4 | 44.8±14.9 | 64.5±11.5 | 38.7±7.3 |
| Height cm | 175.5±6.6 | 179.3±6.3 | 179.4±6.8 | 176.5±6.5 | 179.0±6.4 |
| Education | |||||
| <11 years | 81 (26) | 405 (7) | 11 (7) | 16 (12) | 513 (8) |
| 11–13 years | 149 (47) | 2922 (52) | 77 (50) | 60 (44) | 3208 (52) |
| 14–20+ years | 87 (27) | 2277 (41) | 65 (42) | 59 (44) | 2488 (40) |
| FEV1, L | 4.43±0.92 | 4.42±0.59 | 4.14±0.77 | 3.38±0.61 | 4.39±0.64 |
| FEV1, z-score | 0.71±1.11 | 0.11±0.92 | −0.01±0.88 | 0.06±0.91 | 0.14±0.94 |
| FVC, L | 5.35±1.04 | 5.50±0.76 | 5.18±0.94 | 4.32±0.77 | 5.46±0.80 |
| FVC, z-score | 0.48±1.00 | 0.12±0.89 | −0.03±0.81 | −0.09±0.84 | 0.13±0.90 |
| Females | |||||
| Subjects | 1110 (77) | - | 255 (62) | 385 (74) | 1750 (22) |
| Age years | 47.6±14.1 | - | 50.7±15.2 | 61.7±12.3 | 51.1±15.0 |
| Height cm | 161.5±6.1 | - | 164.8±6.2 | 163.0±6.3 | 162.3±6.3 |
| Education | |||||
| <11 years | 559 (52) | - | 48 (19) | 89 (23) | 696 (41) |
| 11–13 years | 420 (39) | - | 118 (47) | 194 (51) | 732 (43) |
| 14–20+ years | 101 (9) | - | 86 (34) | 98 (26) | 285 (17) |
| FEV1, L | 2.91±0.68 | - | 2.87±0.64 | 2.47±0.55 | 2.81±0.67 |
| FEV1, z-score | 0.39±1.16 | - | 0.14±0.90 | 0.01±0.91 | 0.27±1.09 |
| FVC, L | 3.50±0.73 | - | 3.55±0.76 | 3.09±0.65 | 3.42±0.74 |
| FVC, z-score | 0.19±1.03 | - | 0.10±0.84 | −0.11±0.83 | 0.11±0.97 |
Variables are presented as mean±sd or n (%) as appropriate. Z-scores calculated according to Global Lung Function Initiative (GLI-2012) equations. BCRDS: Bergen Chronic Respiratory Disease Survey; PSWON: Pneumoconiosis Survey of Western Norway; HCRHS: Hordaland County Respiratory Health Survey; BD-HUSK: Bronchodilatation Survey of the Hordaland Health Study; FEV1: forced expiratory volume in 1 s; FVC: forced vital capacity. #: two birth cohorts: 1925–1927 and 1950–1951; ¶: percentage refers to the original population.