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Background: High costs of controller therapies may be a barrier to guideline-recommended asthma treatment. We determined whether eliminating out-of-pocket (OOP) payments among low-income patients with asthma impacted controller medication use. Methods: We applied a controlled interrupted time series design to administrative claims data in British Columbia, Canada from 2017-2020. Cases were individuals with an annual household income 45, 000. We evaluated trends in asthma medication costs, use, the ratio of inhaled corticosteroid (ICS) -containing medications to all asthma medications, excessive use of short-acting β-agonists (SABA) (>1 canister/month), and the proportion of days (PDC) covered by controller therapies. Results: There were 12, 940 cases (62% female, mean age 30. 3 years, SD 14. 9), and 71, 331 controls (55% female, mean age of 31. 3 years, SD 16. 3). Removal of OOP payments increased monthly mean medication costs by 3. 32 (95% CI 0. 08 – 6. 56, 2020 Canadian dollars), days supply of controller medications by 1. 50 days (95% CI 0. 61 – 2. 40), and the ratio of ICS-containing medications to total medications by 4. 20% (95% CI 0. 73% – 7. 66%) compared to the control group. The policy had no effect on PDC by controller therapies (0. 01, 95% CI -0. 01 – 0. 04), but non-significantly decreased the percentage of patients with excessive SABA use (-6. 37%; 95% CI -12. 90% – 0. 16%). Interpretation: Removal of OOP payments increased the dispensation of controller therapies, suggesting cost-related non-adherence could impair optimal asthma management.
JOHNSON et al. (2024) studied this question.