Table 2 Symptoms and lung function at baseline by presence or absence of bronchial hyperresponsiveness (BHR).
| Baseline measures | No BHR (n = 4855) | BHR | p value* | |
|---|---|---|---|---|
| Silent (n = 492) | Symptomatic (n = 478) | |||
| Proportion of total population (%) | 83 | 9 | 9 | – |
| Sex (% female) | 47 | 67 | 64 | <0.001 |
| Mean (SD) age (years) | 40 (11) | 40 (11) | 41 (12) | 0.41 |
| Current smokers (%) | 31 | 29 | 40 | <0.002 |
| Never smokers (%) | 46 | 51 | 38 | 0.0001 |
| Atopic | 20.8 | 32.3 | 42.3 | <0.001 |
| Physician‐diagnosed asthma (%) | 3.2 | – | 34.3 | – |
| Wheeze in last 12 months without cold (%) | 4.7 | – | 26.8 | – |
| Shortness of breath while walking (%) | 20.3 | – | 60.0 | – |
| Chronic cough (%) | 3.5 | – | 14.0 | – |
| Chronic phlegm (%) | 5.3 | – | 15.1 | – |
| COPD† (%) | 5.8 | 13.4 | 12.8 | <0.001 |
| Mean (SD) FEV1 (% pred)31 | 103 (11) | 96 (11) | 93 (12) | <0.001 |
| Mean (SD) FVC (% pred) | 102 (12) | 100 (12) | 97 (13) | <0.001 |
| Mean (SD) FEV1/FVC | 80 (6) | 78 (7) | 77 (8) | <0.001 |
| FEV1/FVC <0.7 (%) | 6 | 13 | 20 | <0.001 |
| Geometric mean methacholine dose‐response slope‡ | 0.7 | 6.5 | 10.0 | <0.001 <0.001 |
*Significance test between individuals without BHR and individuals with asymptomatic BHR.
†COPD was defined as FEV1/FVC <0.70 and no physician's diagnosis of asthma at either survey.
‡Percentage decline in FEV1 per μmol methacholine relative to maximum FEV1.