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

Rationale: High costs of controller therapies may be a barrier to guideline-recommended asthma treatment. Objectives: 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 to 2020. Cases were individuals with an annual household income <$13,750 in whom copays were eliminated in 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-containing medications to all asthma medications, excessive use of short-acting β-agonists (more than one canister per month), and the proportion of days covered by controller therapies. Results: There were 12,940 cases (62% female; mean age, 30.3 yr; standard deviation [SD], 14.9) and 71,331 controls (55% female; mean age, 31.3 yr; SD, 16.3). Removal of OOP payments increased monthly mean medication costs by $3.32 (95% confidence interval [CI], $0.08 to $6.56, 2020 Canadian dollars), days' supply of controller medications by 1.50 days (95% CI, 0.61 to 2.40 d), and the ratio of inhaled corticosteroid-containing medications to total medications by 4.20% (95% CI, 0.73% to 7.66%) compared with the control group. The policy had no effect on the proportion of days covered by controller therapies (0.01; 95% CI, -0.01 to 0.04), but nonsignificantly decreased the percentage of patients with excessive short-acting β-agonist use (-6.37%; 95% CI, -12.90% to 0.16%). Conclusions: Removal of OOP payments increased the dispensation of controller therapies, suggesting cost-related nonadherence could impair optimal asthma management.