The relationship of airway responsiveness to respiratory symptom prevalence has been studied in a cross-sectional analysis of a random subpopulation from a large-scale population study on chronic obstructive pulmonary disease (COPD) being conducted in the Netherlands. In 1,905 subjects with complete data on age, sex, area of residence, smoking habits, and respiratory symptom prevalence, airway responsiveness was assessed by a histamine challenge test. Subjects with a decrease in FEV1 of ⩾ 10% at a histamine concentration of ⩽ 16 mg/ml were considered to be responders. Bronchial hyperresponsiveness appeared to be age dependent, with the proportion of responders increasing from 13% in those 14 to 24 yr of age to 40% in those 55 to 64 yr of age (p < 0.001). Respiratory symptom outcomes included chronic cough, chronic phlegm, dyspnea, bronchitic episodes, persistent wheeze, and asthmatic attacks. Respiratory symptom prevalence rates were significantly higher in responders (p < 0.001 for all symptoms).
Cigarette smoking is known to be related to respiratory symptom prevalence and possibly to bronchial responsiveness. Because of these associations, we examined the relationship of bronchial responsiveness to respiratory symptoms within cigarette smoking categories. For all respiratory symptoms, it was found that, regardless of smoking category, responders were more likely to be symptomatic than were nonresponders. Odds ratios ranged from 1.7 for chronic cough to 4.4 for asthmatic attacks. After controlling for potential confounding variables such as age, sex, and area of residence, both cigarette smoking and bronchial responsiveness were significantly associated with each symptom in a dose-response relationship (p < 0.05). No significant interaction between cigarette smoking and bronchial responsiveness on the production of respiratory symptoms could be detected. In none of these analyses does the dose-response relationship change significantly after adjusting for initial pulmonary function level. We conclude that our results are consistent with the hypothesis that nonspecific bronchial responsiveness is associated with the occurrence of chronic respiratory symptoms.