A population-based study of the burden of severe asthma in Alberta, Canada

Abstract

RATIONALE A comprehensive understanding of the burden of illness and management strategies for severe asthma (SA), especially by disease control, is lacking in Canada. OBJECTIVES The objectives of this study were to describe treatments, exacerbation outcomes and healthcare resource utilization (HCRU) for patients with controlled and uncontrolled SA in Alberta, Canada. METHODS A retrospective cohort of SA patients 12+ years (April 1, 2011 to March 31, 2020) was identified from administrative health data, based on medication dispensed for controlling asthma symptoms, stratified by disease control at index. Treatment patterns were analyzed for incident SA patients. Annualized exacerbation incidence rate ratios (IRR) were estimated throughout follow-up and stratified by disease control at index. Asthma-specific HCRU and direct costs were calculated. RESULTS The study cohort included 74,134 patients (12.4% of eligible asthma patients) of whom 71,099 (95.5%) were classified as controlled and 3,035 (4.1%) as uncontrolled at index. Inhaled corticosteroid + long-acting beta agonist (ICS + LABA) was the most frequent first-line therapy among incident SA patients (n = 53,084), received by 42.7% of patients. A minority received >2 lines of therapy; few received triple therapy. The uncontrolled (at index) versus controlled (at index) cohort had a 5.5 times higher exacerbation rate (IRR: 5.5, 95% CI: 5.1–5.8; p < 0.001), higher HCRU, and higher associated annual costs (mean [SD]: $3,799 [$6,668] uncontrolled vs $1,339 [$2,515] controlled). CONCLUSIONS SA, whether controlled or uncontrolled at index, was associated with ongoing exacerbations and HCRU despite treatment intensification that identified patients as having SA. Some treatment patterns appeared misaligned with guidelines, suggesting potential need for better recognition of asthma severity and escalating therapies.