BRONCHIAL RESPONSIVENESS IN A NORWEGIAN COMMUNITY

Bronchial responsiveness to methacholine was examined in a Norwegian general population sample (n = 490) 18 to 73 yr of age. Altogether, 20 and 6% of the sample had PC20 less-than-or-equal-to 32 mg/ml and PC20 less-than-or-equal-to 8 mg/ml, respectively. The relationship of bronchial responsiveness to the following potential predictors were examined: sex, age, smoking habits, airway caliber (FEV1), FEV1 percent predicted (% FEV1), urban-rural area of residence, occupational airborne exposure in present job, and total serum IgE. After adjusting for age and FEV1, the odds ratio for PC20 less-than-or-equal-to 32 mg/ml was higher for men than for women in smokers and in ex-smokers, but did not vary by sex in nonsmokers, the adjusted odds ratio for PC20 less-than-or-equal-to 32 mg/ml in male compared with female smokers being 8.4 (95% Cl: 2.5-37.4). Irrespective of smoking status the sex- and FEV1-adjusted odds ratio for PC20 less-than-or-equal-to 32 mg/ml fell with increasing age. For every 10-yr increase in age the adjusted odds ratio for PC20 less-than-or-equal-to 32 mg/ml methacholine in nonsmokers decreased by 2.0 (95% Cl: 1.3-3.3). Also FEV1 and %FEV1 were predictors of PC20 less-than-or-equal-to 32 mg/ml after adjusting for sex and age irrespective of smoking status. Bronchial responsiveness (PC20 less-than-or-equal-to 8 mg/ml) was more prevalent in rural than in urban areas, the adjusted odds ratio being 2.5(95% Cl: 1.1-5.9) for bronchial responsiveness in rural compared with urban residence after adjusting for sex, age, smoking habits, and FEV1. Bronchial responsiveness was not associated with present airborne occupational exposure. No relationship was found between sex-and age-adjusted level of serum IgE and bronchial responsiveness. In this general population the following variables were independent predictors of bronchial responsiveness: male sex, younger age, smoking, level of airway caliber (FEV1), level of pulmonary function (% FEV1), and rural area of residence.