Treatment of COPD: relationships between daily dosing frequency, adherence, resource use, and costs.

Background: Medication adherence is important in managing COPD. This study analyzed real-world use of inhaled medications for COPD to characterize relationships between daily dosing frequency, adherence, healthcare resource utilization, and cost.

Methods: This retrospective study used a large administrative claims database covering 8 million insured lives in the US from 1999 to 2006. Patients were stratified based on the recommended daily dosing frequency of their first COPD drug claim following COPD diagnosis. Adherence was measured using proportion of days covered (PDC) over 12 months following treatment initiation. Healthcare resource use included inpatient, outpatient, and emergency room visits. A multivariate regression model assessed the relationship between adherence and one-year healthcare resource use, controlling for demographics, comorbidities, and baseline resource use. Unit healthcare costs were obtained from the 2005 Medical Expenditure Panel Survey, adjusted to 2008 dollars.

Results: Based on a sample of 55,076 COPD patients, adherence was strongly correlated with dosing frequency. PDC was 43.3%, 37.0%, 30.2% and 23.0% for QD, BID, TID, and QID patient cohorts, respectively. Regression analysis showed that one-year adherence was correlated with healthcare resource utilization. For 1000 COPD patients, a 5% point increase in PDC reduced the annual number of inpatient visits (-2.5%) and emergency room visits (-1.8%) and slightly increased outpatient visits (+.2%); the net reduction in annual cost was approximately $300,000.

Conclusion: COPD patients who initiated treatment with once-daily dosing had significantly higher adherence than other daily dosing frequencies. Better treatment adherence was found to yield reductions in healthcare resource utilization and cost.