Background: Lung function determined by spirometry and the severity of dyspnea correlate weakly in asthma patients. We attempted to determine the risk factors in asthma patients having persistent airway obstruction despite of having only mild subjective symptoms, and to examine the possibility of improving FEV1 by treating asthma on the basis of the bronchodilator change in FEV1.
Methods: We examined asthma patients in their 20s and who visited Sagamihara National Hospital for the first time over a period of four years, by reviewing their clinical records. They underwent tests on the bronchodilator change in FEV1 and a test of airway hyperresponsiveness to histamine dihydrochloride.
Results: One hundred thirty-eight subjects (mean age, 25.6 years; 51 males, 87 females; current smoking, 30.4%; history of childhood asthma, 48.6%) were enrolled. Among them, 18.8% (26/138) showed persistent airway obstruction (postbronchodilator FEV1/FVC (%) <80%). Using the multiple logistic regression model, we found that history of childhood asthma and smoking history were the significant isolated risk factors for persistent airway obstruction. Moreover, we determined that the factors associated with the reversibility of airway obstruction in asthma patients without subjective symptoms were history of childhood asthma.
Conclusions: In this study, patients not undergoing treatment for asthma were examined. History of childhood asthma and smoking history may be the risk factors for persistent airway obstruction in the asthma patients with mild subjective symptoms. Tests on the bronchodilator change in FEV1 should be performed in patients with history of childhood asthma and smoking history, even if they have only mild subjective symptoms.