Factors Associated with Guideline-Concordant Maintenance Inhaled Medication for COPD: A Population-Based, Longitudinal Cohort Study

Abstract Rationale: Maintenance inhaled medications are key to managing chronic obstructive pulmonary disease (COPD). Although clinical guidelines provide evidence-based recommendations, many patients either do not receive treatment aligned with these guidelines or have poor adherence to recommended regimens, leading to increased risk of exacerbations and medication-related adverse reactions. We examined trends in the initiation of guideline-concordant medication and adherence to such treatment after initiation, and evaluated patient and health system factors associated with each. Methods: We conducted a population-based cohort study using administrative data from British Columbia, Canada, from 2011 to 2022, which included outpatient medication dispensing records without records of drug samples. Patients aged ≥ 40 years with newly physician-diagnosed COPD were included. Outcomes were analyzed per patient-year from diagnosis. Guideline-concordant medication use was assessed by exacerbation risk, categorized as low risk (≤1 outpatient exacerbation and no hospitalization in the previous year) or high risk (≥2 outpatient exacerbations or ≥1 hospitalization in the previous year). We evaluated the factors associated with 1) the initiation of guideline-concordant maintenance inhaled medication using logistic regression and 2) adherence to guideline-concordant medication in each year after initiation, measured as proportion of days covered (PDC), using linear regression with generalized estimating equations. The initiation of treatment was defined as the first patient-year after diagnosis in which patients received guideline-concordant maintenance inhaled medication of any duration. Results: We identified 88,002 patients with COPD, with a mean follow-up of 6.22 years (SD 2.66). Of these, 37.39% never received any maintenance inhaled medication during follow-up, and 31.91% initiated guideline-concordant treatment. Among initiators, the mean PDC for guideline-concordant medication was 0.30. Patients at high risk of exacerbations initiated guideline-concordant therapy more often than those at low risk (mean 66.21% vs. 13.21%) and had a higher mean PDC (0.58 vs. 0.24) per patient-year. Overtreatment with inhaled corticosteroids in patients at low risk of exacerbation accounted for 70.33% of guideline-discordant regimens, and 68.31% of these patients had no history of asthma. Pulmonologist care and additional outpatient visits were associated with both increased initiation (OR 4.80, 95% CI: 4.58–5.03, and 1.25, 95% CI: 1.24–1.26, respectively) and adherence (PDC increase of 0.03, 95% CI: 0.02–0.03, and 0.004, 95% CI: 0.003–0.005, respectively) to guideline-concordant medications. Conclusions: Guideline-concordant use of maintenance inhaled medications is low in COPD. Addressing barriers at multiple levels of care delivery may improve evidence-based COPD management.