| Independent variables | Dependent variables | |
| PD15 ≤1.6 mg | PD15 ≤0.4 mg | |
| Age >47 years | 0.70 (0.36–1.38) | 0.63 (0.17–2.36) |
| Female# | 2.14 (1.08–4.24) | 1.05 (0.31–3.53) |
| FEV1 <80% pred | 4.58 (2.07–10.12) | 10.75 (3.20–36.11) |
| Family history of asthma¶ | 1.64 (0.75–3.62) | 1.42 (0.34–5.97) |
| Allergy¶,+ | 0.63 (0.33–1.21) | 0.48 (0.15–1.60) |
| Wheezing or asthma in childhood¶ | 3.66 (1.22–11.05) | 2.18 (0.23–21.11) |
| Smoking history§ | ||
| Non smokers | 1 | 1 |
| <15 pack-years | 0.92 (0.41–2.07 | 1.51 (0.22–10.23) |
| ≥15 pack-years | 3.87 (1.77–8.43) | 9.91 (1.83–53.53) |
Data are presented as OR (95% CI). Bronchial hyperresponsiveness (BHR) tested in April–June was included in the model, nonsignificant (for PD15 ≤1.6 mg OR 0.95, 95% CI 0.47–1.92 and for PD15 ≤0.4 mg OR 1.98, 95% CI 0.60–6.52). Environmental tobacco smoke exposure at work included in the model (for BHR OR 2.02, 95% CI 1.00–4.10, and for marked BHR OR 1.98, 95% CI 0.60–6.52) did not change the significance of the factors. PD15: provocative dose of histamine inducing a 15% fall in forced expiratory volume in 1 s (FEV1); % pred: % predicted. #: males as reference group; ¶: “no” as reference group; +: atopy or symptoms of allergic rhinoconjunctivitis; §: in pack-years, current and ex-smokers included.