| Category of change in smoking behaviour | Subjects n | Change in bonchial reactivity slope# % (95% CI) | p-value |
| Persistent smokers | 601 | Ref. | |
| Persistent ex-smokers | 606 | -27.7 (-37.9– -15.9) | <0.001 |
| Quitters | 250 | -23.9 (-37.8– -6.8) | 0.008 |
| Uptakers | 99 | -17.3 (-37.6–9.4) | 0.202 |
| Intermittent smokers | 100 | -12.8 (-30.0–8.8) | 0.156 |
| Persistent never-smokers | 1349 | -24.6 (-33.5– -14.5) | <0.001 |
Ref.: reference category. #: percentage change in bronchial reactivity slope from the baseline value; bronchial reactivity slope is defined as percentage change in forced expiratory volume in 1 s (FEV1) per micromole of methacholine; estimates are from a mixed linear regression model with random effects for area and adjusting for sex, age, age squared, body mass index (BMI), change in BMI, atopy, FEV1, forced expiratory volume at 25–75% of forced vital capactiy (FVC), FVC, occurrence of colds and seasonal terms.