The Impact of Eliminating Out-of-Pocket Payments on Asthma Medication Use

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 <$13,750 in whom copays were eliminated on January 2019; there was no change in public coverage for the control group with annual 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.