Adherence to Inhaled Medications and Its Effect on Healthcare Utilization and Costs Among High-Grade Chronic Obstructive Pulmonary Disease Patients

Background: Adherence to inhaled medication regimens affects chronic obstructive pulmonary disease (COPD) prognosis and quality of life, and reduces the use of healthcare services, resulting in cost savings.

Objectives: To examine the effects of adherence to inhaled medication regimens on healthcare utilization and costs in high-grade COPD patients.

Methods: We performed an observational retrospective cohort study using a longitudinal data set from the Korean Health Insurance Review and Assessment Service (2008-2013) containing healthcare services' information for 50 million beneficiaries. The study population was high-grade COPD patients. "Adherent" was defined as a patient attaining a medication possession ratio (MPR) ≥ 80%. We estimated the effects of adherence on the use of intensive care units (ICUs) and emergency rooms (ERs) using a multivariate logistic regression, and estimated the effects on costs (all-cause and COPD-related) using a generalized linear model, with adjustment for patient sociodemographic characteristics, health status, and comorbidities.

Results: Of 9086 high-grade COPD patients, adherence declined from 34.7 to 22.3% over 4 years. Adherence was inversely associated with use of ICUs and costs, and this association got stronger as the adherence period lengthened. Over the 4-year period, the adherent group had a lower likelihood of using ICUs [odds ratio (OR) = 0.74, 95% confidence interval (CI) 0.60-0.91] than the non-adherent group. Similarly, the adherent group had a 10.4% lower all-cause cost (p < 0.001) and an 11.7% lower COPD-related cost (p < 0.0001) versus the non-adherent group.

Conclusions: Adherence reduces healthcare utilization and costs, so adherence is not only clinically effective but also economically efficient. However, less than one-quarter of this population remained adherent over the 4-year period, suggesting that strategies are needed to improve adherence.