Background: Understanding the population-level impact of drugs with corticosteroid-sparing effects in severe asthma requires knowledge of ‘real-world’ trends in exposure to systemic corticosteroids. Objectives: To estimate the extent, trends, and factors associated with exposure to oral corticosteroids (OCS) in a large, population-based severe asthma cohort.

Methods: We used administrative health databases of British Columbia, Canada (1997–2014) and validated algorithms to create a cohort of severe asthma patients. Exposure to OCS was measured in two ways during a year: chronic exposure as receiving on average ≥2.5mg/day (prednisone-equivalent) OCS, and episodic use as the number of distinct episodes of OCS exposure for up to 14 days. Trends and factors associated with them exposure on three time axes (calendar year, age, and time since diagnosis) were evaluated using Poisson regression.

Results: 21,144 patients (55.4% female; mean entry age 28.7) contributed 40,803 follow-up years, in 8.2% of which OCS was used chronically. Chronic OCS use declined by 3.8%/calendar year (P<0.001). The average number of episodes of OCS use was 0.89/year, which increased by 1.1%/calendar year (P<0.001). Trends remained significant for both exposure types in adjusted analyses. Both chronic and episodic exposure increased by age and time since diagnosis.

Conclusions: There was a secular increasing upward downward trend in chronic OCS use and a modest downward upward trend in episodic use in this population-based severe asthma cohort. Whether the increasing use of biologics in severe asthma will accelerate the downward trends in chronic use or curb the upward trend in episodic OCS use should be monitored in future studies.