Association of nasal inflammation and lower airway responsiveness in schoolchildren based on an epidemiological survey

BACKGROUND/AIMS We sought to increase our understanding of the rhinitis-asthma relationship and improve strategies for the treatment of patients with these diseases. The aim of this study was to identify a connection between upper airway inflammation and lower airway responsiveness. METHODS We counted eosinophils on nasal smears, and performed spirometry, allergic skin tests, and methacholine challenge tests in 308 schoolchildren plus a questionnaire on respiratory symptoms. The methacholine concentration causing a 20% fall in forced expiratory volume in 1 second (PC20 < 25 mg/mL) was used as the threshold of bronchial hyperresponsiveness (BHR). RESULTS In total, 26% of subjects had positive nasal eosinophils on a smear, and 46.2% of subjects had BHR at < 25 mg/mL methacholine PC20. Nasal symptoms were higher in subjects with than without nasal eosinophils (p = 0.012). Asthma symptoms did not differ between subjects with and without nasal eosinophils. Nasal eosinophils were higher in subjects with atopy than those without (p = 0.006), and there was no difference in PC20 methacholine according to atopy (15.5 ± 1.07 vs. 17.5 ± 0.62; p > 0.05). No difference in BHR was detected when comparing subjects with and without nasal eosinophils. There were significant differences in the PC20 between subjects with greater than 50% nasal eosinophils and without nasal eosinophils (11.01 ± 2.92 mg/mL vs. 17.38 ± 0.61 mg/mL; p < 0.001). CONCLUSIONS These findings demonstrated that nasal eosinophilic inflammation might contribute to lower airway responsiveness in schoolchildren, based on an epidemiological survey.