| All | Without BHR | With BHR | |
| Cohort participants included in study, N (%) | 4426 (100) | 3800 (85.9) | 626 (14.1) |
| Women, N (%) | 2169 (49.0) | 1758 (46.3) | 411 (66.7) |
| Baseline characteristics | |||
| Mean (SD) age at baseline (years) | 40.5 (11.3) | 40.3 (11.2) | 41.4 (11.7) |
| BMI at baseline (kg/m2) | 23.7 (3.5) | 23.6 (3.4) | 23.9 (4.0) |
| Total IgE >100 kU/l, N (%) | 821 (20.1) | 657 (18.6) | 164 (29.3) |
| Atopy, N (%) | 908 (21.0) | 680 (19.6) | 159 (28.0) |
| Geometric mean (SD) methacholine response slope§ | 1.0 (3.7) | 0.7 (2.9) | 7.1 (2.8) |
| Non-smokers, N (%) | 2069 (46.8) | 1780 (46.9) | 289 (46.3) |
| Former smokers, N (%) | 1016 (23.0) | 900 (23.7) | 116 (18.6) |
| Current smokers, N (%) | 1337 (30.2) | 1118 (29.4) | 219 (35.1) |
| Mean (SD) pack-years among ever smokers at baseline | 16.5 (17.7) | 16.0 ( 17.3) | 19.7 (19.6) |
| ETS exposure reported at baseline, N (%) | 879 (19.9) | 757 (19.9) | 122 (19.6) |
| Gas, fumes and dust exposure at work at baseline, N (%) | 1348 (30.6) | 1144 (30.2) | 204 (32.6) |
| Mean (SD) FEV1 (% pred) | 101.6 (12.2) | 102.7 (11.8) | 94.7 (12.1) |
| Mean (SD) FVC (l) | 4.6 (1.0) | 4.7 (1.0) | 4.2 (1.0) |
| Mean (SD) FEV1/FVC (%) | 79.8 (6.8) | 80.2 (6.6) | 77.3 (7.2) |
| FEV1/FVC <0.7, N (%) | 324 (7.5) | 232 (6.3) | 92 (15.0) |
| Wheezing without cold in last 12 months, N (%) | 207 (4.7) | 149 (3.9) | 58 (9.3) |
| Chronic phlegm, N (%) | 222 (5.1) | 181 (4.8) | 41 (6.7) |
| Chronic cough, N (%) | 157 (3.6) | 119 (3.1) | 38 (6.1) |
| Woken up at night by shortness of breath, N (%) | 117 (2.6) | 94 (2.5) | 23 (3.7) |
| ⩾1 of respiratory symptoms above, N (%) | 561 (12.7) | 438 (11.5) | 123 (19.7) |
| Selected follow-up characteristics | |||
| BMI at follow-up (kg/m2) | 25.7 (4.2) | 25.7 (4.1) | 26.1 (4.9) |
| Mean (SD) weight change during follow-up (kg) | 5.6 (6.1) | 5.5 (6.1) | 5.7 (6.3) |
| Never smokers, N (%) | 1905 (43.0) | 1631 (43.0) | 267 (43.0) |
| Ever smokers, N (%) | 2521 (57.0) | 2164 (57.0) | 357 (57.0) |
| Mean (SD) pack-years¶ | 6.1 (7.6) | 6.0 (7.6) | 7.0 (7.8) |
| ETS exposure reported at follow-up, N (%) | 585 (13.2) | 507 (13.3) | 78 (12.5) |
| Gas, fumes and dust exposure at work at follow-up, N (%) | 1143 (27.9) | 1013 (28.7) | 130 (22.9) |
| GST genotypes | |||
| GSTP1 Ile105Val, N (%) | |||
| Ile/Ile | 2071 (46.8) | 1792 (47.2) | 253 (44.6) |
| Ile/Val | 1945 (43.9) | 1650 (43.4) | 266 (46.9) |
| Val/Val | 410 (9.3) | 358 (9.4) | 48 (8.5) |
| Ile/Val or Val/Val | 2355 (53.2) | 1828 (52.5) | 314 (55.4) |
| GSTM1, N (%) | |||
| No homozygous deletion | 2100 (47.5) | 1802 (47.5) | 298 (47.7) |
| Homozygous deletion | 2322 (52.5) | 1995 (52.5) | 327 (52.3) |
| GSTT1, N (%) | |||
| No homozygous deletion | 3600 (81.4) | 3090 (81.4) | 510 (81.6) |
| Homozygous deletion | 822 (18.6) | 707 (18.6) | 115 (18.4) |
BHR, bronchial hyperresponsiveness; BMI, body mass index; FEV1, forced expiratory volume in 1 s; FVC, forced vital capacity; ETS, environmental tobacco smoke; GST, glutathione S-transferase.
*Given as absolute numbers and percentages for categorical variables and as mean (SD) for continuous variables.
†Numbers do not consistently add up to full sample size owing to missing information on some of the presented characteristics.
‡Atopy was defined as a positive skin prick test reaction to at least one common allergen.
§Percentage decrease in FEV1 per μmol methacholine challenge
¶Pack years smoked during follow-up among ever smokers.