Factors associated with guideline-concordant maintenance inhaled medication for COPD: a population-based, longitudinal cohort study

BACKGROUND: Despite guideline recommendations, many patients with chronic obstructive pulmonary disease (COPD) do not receive or persist with guideline-concordant maintenance inhaled medications. We examined patient and health system factors associated with guideline concordance and persistence. METHODS: We conducted a population-based cohort study using administrative data from British Columbia, Canada (2011-2022). Patients aged ≥40 years with newly diagnosed COPD were included. Patients were classified as having high risk (≥2 outpatient or ≥1 inpatient exacerbation in the prior year) or low risk (≤1 outpatient exacerbation) of exacerbations, which we used to determine whether dispensed medications were concordant with guidelines. We used separate generalised linear models to evaluate the association between patient, clinical and health system factors and the initiation of guideline-concordant medications and subsequent persistence. RESULTS: We included 71 996 patients with a mean follow-up of 6.15 years (SD 2.65). 30.42% of patients initiated guideline-concordant treatment. Among those who initiated, the mean proportion of days covered (PDC) by guideline-concordant regimens was 31.93%. Patients at high risk of exacerbations initiated guideline-concordant regimens more often than those at low risk (mean 70.4% vs 13.3%) and had a higher mean PDC (57.33% vs 26.35%) per patient-year. Pulmonologist care and additional outpatient visits increased both initiation (OR 5.14, 95% CI 4.88 to 5.41 and OR 1.25, 95% CI 1.24 to 1.26, respectively) and persistence (OR 1.13, 95% CI 1.09 to 1.17 and OR 1.019, 95% CI 1.015 to 1.024, respectively) with guideline-concordant medications. CONCLUSION: Guideline-concordant use of maintenance inhaled medications is low. Increased access to outpatient and specialist care may support COPD management.