Association between seasonal patterns of the airway response to humid air and dynamics of lung function and disease control in asthma patients

Abstract

Background: Previously we found that osmotic airway hyperresponsiveness (OAH) may fluctuate in its degree depending on the seasonal humidity. Besides, the onset of humid season is usually accompanied by deterioration in bronchial obstruction and disease control in asthma patients.

Objectives: We aimed to establish a possible relationship between seasonal patterns of OAH and dynamics of asthma symptoms and lung function depending on air humidity.

Methods: Eighty-two patients with mild-to moderate asthma aged 40.5±1.07 years were enrolled. The patients were examined during two consecutive visits in dry (humidity <70%) and humid (humidity >70%) seasons. Lung function was measured by spirometry before and after the test with 3-min inhalation of nebulized distilled water. Asthma control was evaluated by Asthma Control Test (ACT) questionnaire.

Results: All the patients were divided into four groups according to dynamics of OAH status: 1 – stable negative OAH (48%); 2 – OAH onset in humid season (35%); 3 – OAH disappeared in humid season (4%); 4 – stable positive OAH (13%). Patients in group 2 had significant negative seasonal dynamics of airway patency and asthma control. In these patients we observed a decrease of FEV1 (from 103.0±3.15% to 86.8±3.38%, p=0.001), FEV1/FVC (from 93.6±1.85% to 84.5±2.17%, p=0.001) and ACT score (from 21.0 (17.0-24.0) to 17.0 (13.0-22.0), p=0.005). Patients in the other groups did not show any significant changes.

Conclusions: Seasonal dynamics of OAH, asthma symptoms and lung function seem to be interrelated. Deterioration in ACT score and airway patency in humid season coincides with the appearance of OAH.