Sadatsafavi and colleagues address the question of the safety of long-acting β-agonists (LABA) in asthma with and without the concomitant use of inhaled corticosteroids (ICS).1 They carried out a study within the administrative healthcare databases of the province of British Columbia, Canada. The universal healthcare system provides healthcare for all residents of the province and includes coverage of prescription drugs. The results of the study are therefore based on a complete population avoiding the exaggeration of benefit and the minimisation of harm that may result in randomised controlled trials (RCTs) which often exclude those with comorbid disease. Within a cohort of more than 120 000 subjects, aged between 12 years and 45 years at study initiation, who were users of asthma medications, they identified more than 3000 hospitalisations for asthma. They then compared the medication used in the 12 months prior to the asthma hospitalisation with the use of asthma medications among control subjects with similar asthma severity that had not been hospitalised at that time.

Several of the results reported are of interest. First, irregular use of maintenance asthma therapy with ICS or the combination ICS/LABA is substantially more common than regular use. This is not new,2 but is particularly troublesome for the ICS/LABA combination since it is only clearly indicated in subjects who do not achieve control of their asthma with regular ICS use. Second, the risk of an asthma hospitalisation, …