BRONCHIAL HYPERRESPONSIVENESS AS A PREDICTOR OF WHEEZING IN A FOLLOW-UP-STUDY OF HEALTHY-MEN

We assessed the relationship between bronchial hyperresponsiveness (BH R) and the onset of wheezing 5 years later, by epidemiological analysi s of 194 working men without asthma or wheezing at the first examinati on. In 1985/1986 and 1990/1991, subjects answered a British Medical Re search Council questionnaire and performed lung function measurements and methacholine challenge tests (total dose 6 mg). BHR was measured i n three ways: (1) FEV(1) fall greater than or equal to 20% (PD20+); (2 ) the two-point response slope expressed as percentage decline of FEV( 1)/dose, and (3) a four-parameter model: FEV(1) at dose (d)/prechallen ge FEV(1) = ONE-k(d-delta)(+)(alpha), where 'k' is the slope of the re lative variation of FEV(1) with the dose, 'delta' the threshold dose, and 'alpha' a shape factor. In the 13 new wheezers, the mean values of the two-point slope and of k were significantly increased, and the pr oportion of reactors was almost threefold (the latter was not statisti cally significant). Among nonsmokers, delta was significantly lower in new wheezers than in the others, whereas the slope and k had similar mean values. Among smokers, new wheezers had increased mean values for the slope and k, and an increased proportion of reactors, whereas del ta was not decreased. Thus, BHR was a significant predictor of wheezin g, independent of the method of analysis. Moreover, the model distingu ished between two components of bronchial response: wheezing was predi cted by sensitivity (delta) in nonsmokers, and by reactivity (k) in sm okers.