PREVALENCE OF BRONCHIAL HYPERRESPONSIVENESS IN THE SOUTHERN, CENTRAL AND NORTHERN PARTS OF SWEDEN

Studies have suggested that there is a higher prevalence of asthma in northern Sweden than in southern Sweden. Bronchial hyper-responsivenes s (BHR) has been shown to be associated with asthma. The aim of this s tudy was to explore the prevalence of bronchical hyper-responsiveness in different parts of Sweden. As part of the European Community Respir atory Health Survey (ECRHS), interviews, skin prick tests, lung functi on tests and methacholine provocation tests of the airways were perfor med in 1448 randomly selected subjects in southern, central and northe rn Sweden. The Mefar dosimeter was used according to the ECRHS protoco l. The responsiveness was calculated both as the PD20 and as the dose response slope (DRS). BHR was defined as a PD20 of less than or equal to 1.6 mg. Atopy was defined as at least one skin prick test of greate r than or equal to 3 mm. The prevalence of BHR was 12.7%, 10.6% in men and 15.0% in women. No difference in prevalence was found between the three different regions of Sweden. The prevalence of BHR was higher i n women than in men and higher in smokers than in non-smokers. Using m ultiple logistic regression, with BHR as the dependent variable, atopy , being female, having a low FEV1 (% predicted) and smoking (both own and passive) increased the odds of having BHR, while age and the regio n of Sweden did not influence BHR. Defining BHR as a PD20 of less than or equal to 1.0 mg or a PD20 of less than or equal to 2.0 mg did not change this. Multiple regression using log DRS as the dependent variab le produced the same result. Both BHR and increasing DRS were associat ed with self-reported wheezing, attacks of shortness of breath during the daytime at rest or after strenuous activity, being awakened by a f eeling of tightness in the chest or an attack of shortness of breath. In subjects without self-reported asthma, BHR was associated with self -reported wheezing and attacks of shortness of breath after strenuous activity. In conclusion, we found that the prevalence of BHR in the th ree investigated areas was 12.7%. We found a trend towards a higher pr evalence of BHR in the most northerly of the study areas, but the diff erence between the areas was not statistically significant. BHR and DR S were associated with atopy, smoking, female sex and FEV1 (%predicted ). The reporting of symptoms from the airways was associated with the degree of bronchical responsiveness.