Decrements in lung function associated with workplace exacerbation of asthma

A subset of adults with asthma demonstrate irreversible airway obstruction (IAO) or other decrements in lung function. The aim of this study was to examine whether a history of workplace exacerbation of asthma (WEA) was associated with these outcomes in adults with asthma.

170 adults aged 20-47 (mean age=36) underwent lung function testing pre- and post- bronchodilator. Forced expiratory volume in one second (FEV₁) and forced vital capacity (FVC) were measured. Obstruction was defined as a pre-bronchodilator FEV₁ and FEV₁/FVC less than the lower limits of normal (LLN). IAO was defined, among those obstructed, as a post-bronchodilator (post-BD) FEV₁ less then the LLN. Associations between lung function outcomes and WEA and other variables were evaluated using regression modeling.

Fifteen (8.8%) of the 170 adults tested had IAO. Demographic characteristics, asthma severity, and WEA status were not associated with IAO. Based on regression modeling, a lower post-BD FEV₁ was associated with moderately severe (versus mild) asthma among males (-0.371 liter, p=0.02) but not females (+0.106 liter, p=0.30), controlling for gender, age, height, and weight. Also, those with a history of WEA had a lower post-BD FEV₁ (-0.179 liter, p=0.08).

Our study showed no association between IAO and traditional explanatory factors, but did show that IAO can occur in young adults with mild to moderate asthma. A decrement in FEV₁ was associated with WEA, but was of borderline statistical significance (0.05<p<0.10) in this relatively small group of adults with asthma.