Bronchial responsiveness at 8–9 years of age
| 25–32 weeks | 33–34 weeks | 35–36 weeks | Term | |
| Number who had lung function at 8–9 years | 68 | 81 | 248 | 6308 |
| Number (%) who were excluded or did not complete the challenge for the reasons listed below* | 35 (51.5%) | 34 (42.0%) | 90 (36.3%) | 2185 (34.6%) |
| Number (%) who underwent challenge | 33 (48.5%) | 47 (58.0%) | 158 (63.7%) | 4123 (65.4%) |
| Number (%) who responded to methacholine challenge | 9 (27.3%) | 9 (19.1%) | 22 (13.9%) | 646 (15.7%) |
| Geometric mean PD20 in responders (μmol) | 1.20 (0.43, 3.35) | 2.25 (1.08, 4.70) | 2.27 (1.50, 3.42) | 1.71 (1.57, 1.87) |
| Geometric mean PD20 for the whole population who underwent the challenge (μmol) | 6.46 (4.15, 10.04) | 8.86 (7.08, 11.09) | 9.62 (8.65, 10.69) | 8.96 (8.73, 9.19) |
↵* Children did not start or complete the challenge for a number of reasons: the child refused whole/part of session, parent refused, parents did not attend, staff illness/difficulties, need doctor, child ill or taking medications, time restraint, equipment error/failure, staff error (general), child started coughing, child problems/difficulties with task, couldn't get reproducible FEV, excluded due to FEV1 <70% predicted.