Faculty of Pharmaceutical Sciences & UBC Division of Respiratory Medicine
Respiratory Evaluation Sciences Program

Research Theme Asthma

Predictors of inappropriate usage of reliever medications in asthma: a 12-year population-based study


Background : Despite robust evidence on harm, many patients continue to receive excessive rescue medications such as short acting beta agonist agents (SABA). Understanding factors associated with inappropriate use of SABA (IUoS) can help develop better policies to tackle this problem.

Objectives: To identify factors which affect inappropriate use of SABA in a large population-based sample.

Methods: We used administrative health data of British Columbia (BC) between 2002 and 2013. We created a retrospective cohort of individuals between 14 and 55 years of age based on a validated asthma definition. The follow-up time was divided into adjacent 12-months periods. The outcome of interest was IUoS, as defined in a published algorithm. Exposures were demographic variables at baseline and indicators of types and quality of care (fee code for spirometry, care provider specialty) as well as appropriate use of Inhaled corticosteroid (ICS) in the previous year. A generalized linear model was used to examine exposure-outcome associations, controlling for several potential confounding variables.

Results: 352,936 individuals (56% female, average age of 30.2 at entry) satisfied the case definition, generating 2.6 million patient-years. On average, 18.4% of patient-years were categorized as IUoS. The factor most strongly associated with IUoS was appropriate use of corticosteroid; (OR=0.32, 95% CI 0.31-0.32). Female sex (OR=0.95, 95%CI 0.93-0.96) and increasing age was associated with lower odds of inappropriate use, and increasing age OR=0.96, 95% CI 0.96-0.96) were associated with a lower likelihood of inappropriate use (. Among type/quality of care indicators, use of spirometry was associated with 3% reduction in odds of IUoS. Patients with history of visit by respiratory medicine, internal medicine, and allergy/immunization specialist at previous year showed 17%, 16% and 13% lower chance of IUoS, respectively, (Table 1).

Conclusions: Despite proven safety issues, inappropriate SABA use is still high, necessitating further research into its determinants. Several factors belonging to patient and process/quality of care are associated with inappropriate use of SABAs. Guidelines have not been successful in ensuring appropriate asthma treatment especially among patients under the care of primary care providers.

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