Increased level of bronchial responsiveness in inactive children with asthma

We estimated the association between bronchial responsiveness and hours of exercise per week in children with and without asthma. A random sample of s chool children (n = 2188), 6-16 years old, was enrolled in a cross-sectiona l study of asthma in Oslo using the ISAAC questionnaire. Lung function and bronchial responsiveness (BR) using methacholine was measured in a random s ample of 80 children with asthma, wheeze and no asthma/no wheeze. The relat ion between hours of exercise per week and BR [log (DRS)] was estimated by linear regression. Sex and age were included as covariates. Hours of exerci se were categorized in: none, 30 min, 1 h, 2-3 h, 4-6 h and 7 h or more. Th e mean values of log (DRS) were different in the low and high exercise grou ps for children with asthma (P = 0.02), whereas there was no effect of exer cise on BR for children without asthma. BR increased with decreasing hours of exercise per week in children with asthma. The bronchial responsiveness decreased with 0.11 (95% CI - 0.20, -0.01) pr unit in scale. This pattern w as not present in children without asthma. The results suggest that there i s a relation between hours of exercise per week and bronchial responsivenes s in children with asthma. (C) 2001 Harcourt Publishers Ltd.