ABSTRACT
BACKGROUND: Impaired symptom perception is often listed as a risk factor for life-threatening asthma, but there is limited evidence to support this. OBJECTIVE: We aimed to determine whether impaired perception of bronchoconstriction (BC) and/or dynamic hyperinflation (DH) are risk factors for severe asthma exacerbations. METHODS: In this prospective cohort study, individuals with asthma underwent high-dose methacholine challenge testing. Changes in forced expiratory volume in 1 second (FEV1) (% predicted) and inspiratory capacity (IC) (% predicted) were measured to assess the degree of BC and DH, respectively, during high-dose methacholine bronchoprovocation. Participants rated dyspnea intensity during testing and were categorized as poor, normal, and over perceivers of BC and DH based on perception scores at standardized changes (20%, 30%, and 40%) in FEV1 (% predicted) and IC (% predicted). We compared the rates of severe asthma exacerbations (defined as one of emergency department [ED] visit or hospitalization) between groups, using Ontario's administrative health databases. RESULTS: Poor perceivers had higher rates of ED visits and hospitalizations as compared with normal perceivers at 4 of 6 threshold decreases in FEV1 and IC studied. Poor perceivers of severe DH had a 6-fold increase in asthma exacerbations (odds ratio, 5.7; 95% confidence interval, 1.31-25.03). CONCLUSIONS: Health services utilization is increased in individuals with asthma who have poor perception of BC and DH. Poor perceivers of severe DH appear to be at the highest risk of exacerbations.
