THE UNIVERSITY OF BRITISH COLUMBIA
The role of long-acting β-agonists (LABA) added to inhaled corticosteroids (ICS) in the management of asthma is extensively debated. We thought to assess the risk of asthma-related hospitalisation in individuals who regularly filled prescriptions for ICS+LABA compared to those who regularly filled prescriptions for ICS alone or LABA alone, and compared to those who did not regularly fill such medications. METHODS: Using administrative health databases of the province of British Columbia (BC), Canada, from 1997 to 2012, we conducted a nested case-control analysis of a cohort of asthma patients. Cases were defined as those who experienced asthma-related hospitalisation after the first year of their entry into the cohort. For each case, up to 20 controls were matched based on age, sex, date of cohort entry, and several measures of asthma severity. We categorised individuals as regularly exposed, irregularly exposed, or non-exposed to ICS alone, LABA alone, or ICS+LABA based on dispensation records in the past 12 months. The primary outcome measures were the rate ratio (RR) of the asthma-related hospitalisation among categories of regular exposure. RESULTS: 3319 cases were matched to 43 023 controls. The RR for regular dispensation of ICS+LABA was 1.14 (95% CI 0.93 to 1.41) compared with regular dispensation of ICS alone and 0.45 (95% CI 0.29 to 0.70) compared with regular dispensation of LABA alone. Those who regularly dispensed LABA had to dispense an ICS for at least three quarters of a year to reduce their risk to that of those who did not dispense LABA. CONCLUSIONS: Regular dispensation of ICS+LABA was not associated with an increased risk of asthma-related hospitalisation compared with regular dispensation of ICS alone. Adherence to ICS in patients who regularly receive ICS+LABA seems to be an important factor in the prevention of adverse asthma-related outcomes.