Impact of adherence to treatment with inhaled corticosteroids/long-acting β-agonists on asthma outcomes in the United States

Background: Suboptimal adherence to maintenance medication has been associated with poor outcomes in asthma. This study examined single-inhaler inhaled corticosteroid (ICS)/long-acting beta 2 agonist (LABA) adherence and asthma-related outcomes. Methods: This retrospective observational study of patients with asthma initiating ICS/LABA used data from IQVIA PharMetrics Plus (1 January 2014-31 March 2019). Patients included were >= 18 years old and had >= 12 months continuous eligibility before, and >= 180 days followup after, the index date. Adherence was measured as proportion of days covered ([PDC] adherent >= 0.8; non-adherent <0.8) each quarter, with outcomes measured each subsequent quarter. Endpoints were asthma-related overall and severe (inpatient/emergency department [ED] visit) exacerbations, rescue medication use, and asthma-related healthcare resource utilization and costs. Regression models evaluated associations between adherence and outcomes, controlling for repeated measures and differences in baseline characteristics. Results: Overall, 50,037 patients were included (mean age 45.3 years; mean follow-up 23.3 months). Adherent patients were less likely to experience asthma-related overall (adjusted odds ratio [aOR] 95% confidence interval [CI]: 0.942 [0.890, 0.998]; p = 0.041), or severe exacerbations (aOR [95% CI]: 0.778 [0.691, 0.877]; p < 0.001) per quarter versus non-adherent patients. Adherent patients had lower severe exacerbation rates (adjusted rate ratio [aRR] [95% CI]: 0.792 [0.702, 0.893]; p < 0.001) but similar overall exacerbation rates (aRR [95% CI]: 0.993 [0.945, 1.044]; p = 0.783) versus non-adherent patients. The odds of rescue medication use were lower per 20% PDC increase (aOR [95% CI] short-acting 132 agonist: 0.991 [0.985, 0.996]; p = 0.001; oral corticosteroid: 0.988 [0.982, 0.995]; p < 0.001). Adherent patients were less likely to visit EDs per quarter (aOR [95% CI]: 0.775 [0.680, 0.883]; p < 0.001) and odds of hospitalization were lower per 20% PDC increase (aOR [95% CI]: 0.930 [0.881, 0.982]; p = 0.009). Across most measures, adherent patients incurred lower costs. Conclusion: This real-world study highlights the short-term clinical and economic benefits of ICS/LABA adherence in asthma, particularly in reducing severe exacerbations.

Automated summary

This study highlights the importance of adherence to inhaled corticosteroid/long-acting beta 2 agonist treatment in asthma patients. Adherent patients had lower rates of overall and severe exacerbations, reduced rescue medication use, and lower healthcare resource utilization and costs. The findings emphasize the short-term clinical and economic benefits of medication adherence in asthma management.