Bronchial hyperresponsiveness in an adult population in Helsinki: decreased FEV1, the main determinant

INTRODUCTION Bronchial hyperresponsiveness (BHR) elevates the risk for development of respiratory symptoms and accelerates the decline in forced expiratory volume in the first second (FEV1 ). We thus aimed to assess the prevalence, determinants and quantity of BHR in Helsinki. OBJECTIVES This study involved 292 randomly selected subjects age 26-66years, women comprising 58%. METHODS Following a structured interview, a spirometry, a bronchodilation test, and a skin-prick test, we assessed a bronchial challenge test with inhaled histamine using a dosimetric tidal breathing method. Results included the provocative dose inducing a decrease in FEV1 by 15% (PD15 FEV1 ) and the dose-response slope. For statistical risk factor-analyses, the severity of BHR was considered; PD15 values ≤1.6mg (BHR) and ≤0.4mg [moderate or severe BHR (BHRms )] served as cut-off levels. RESULTS BHR presented in 21.2% and BHRms in 6.2% of the subjects. FEV1<80% of predicted [odds ratio (OR) 4.09], airway obstruction (FEV1 /forced vital capacity<88% of predicted) (OR 4.33) and history of respiratory infection at age <5 (OR 2.65) yielded an increased risk for BHR as ORs in multivariate analysis. For BHRms , the determinants were decreased FEV1 below 80% of predicted (OR 27.18) and airway obstruction (OR 6.16). Respiratory symptoms and asthma medication showed a significant association with BHR. CONCLUSIONS Of the adult population of Helsinki, 21% showed BHR to inhaled histamine. The main determinants were decreased FEV1 and airway obstruction. Quantitative assessment of BHR by different cut-off levels provides a tool for characterization of phenotypes of airway disorders in epidemiologic and clinical studies.