Relationship between duration of disease and bronchial responsiveness in 6–8 years old children with asthma

Bronchial hyperresponsiveness (BHR) is a characteristic feature of asthma, and is considered to be one of the major consequences of airway inflammation and remodeling. BHR is usually defined as an increased sensitivity of the airways to inhaled nonsensitizing bronchoconstrictor stimuli, which is evaluated by measuring the dose or concentration (PC20) of inhaled methacholine or histamine that causes a 20% fall in forced expiratory volume in 1 second (FEV1) from baseline. However, there is accumulating evidence that BHR is a more complex functional abnormality that comprises more than just hypersensitivity. Recently, Gibbons et al. proposed a novel indirect method for detection of excessive bronchoconstriction in patients with mild, newly diagnosed asthma. They retrospectively measured the percentage fall in forced vital capacity (FVC) at PC20 (∆FVC), which reflects gas trapped at that point of the dose-response curve due to excessive bronchoconstriction, and found that this index of airway closure was not related to the PC20. A number of cross-sectional studies have shown that duration of asthma was associated with lower levels of lung function. Moreover, multiyear prospective studies of both children and adults with asthma revealed worsening pulmonary function over time, which suggest that childhood asthma seems to be associated with reduced lung function growth, and adult asthmatics may also have increased decline in lung function during their life. However, a few studies have tried to relate the duration of asthma to bronchial responsiveness in the patients with asthma. The Childhood Asthma Management Program (CAMP) study demonstrated that duration of disease correlated negatively with levels of bronchial responsiveness in children with mild-to-moderate Allergy Asthma Respir Dis 2(1):23-29, March 2014 http://dx.doi.org/10.4168/aard.2014.2.1.23 pISSN: 2288-0402 eISSN: 2288-0410