Table 3

 Incident respiratory symptoms during follow up according to the level of airway responsiveness in subjects asymptomatic at baseline

Level of airway responsiveness (PC20)(mg/ml)No of subjectsNo of incident respiratory symptoms*
PC20, concentration of methacholine provoking a 20% fall in FEV1; AHR, airway hyperresponsiveness.
*Wheezing, shortness of breath, chest tightness, cough, respiratory complaints upon exertion.
†Percentage of subjects complaining of two or more new respiratory symptoms among those with a given PC20 level who developed new respiratory symptoms.
⩽419549/19 (47.4%)
4–819404/19 (21.1%)
With AHR3813 (34.2%)
8–16368614/36 (38.9%)
16–3241538/41 (19.5%)
32313819/313 (2.9%)
Without AHR39031/390 (7.9%)
Overall428301444/428 (10.3%)