Abstract
RATIONALE: Among individuals with chronic obstructive pulmonary disease (COPD), depression is one of the most common yet underrecognized and undertreated comorbidities. Although depression has been associated with reduced adherence to maintenance medications used in other conditions, such as diabetes, little research has assessed the role of depression in COPD medication use and adherence. OBJECTIVES: The objective of this study was to assess the impact of depression on COPD maintenance medication adherence among a nationally representative sample of Medicare beneficiaries newly diagnosed with COPD. METHODS: We used a 5% random sample of Medicare administrative claims data to identify beneficiaries diagnosed with COPD between 2006 and 2010. We included beneficiaries with 2 years of continuous Medicare Parts A, B, and D coverage and at least two prescription fills for COPD maintenance medications after COPD diagnosis. We searched for prescription fills for inhaled corticosteroids, long-acting β-agonists, and long-acting anticholinergics and calculated adherence starting at the first fill. We modeled adherence to COPD maintenance medications as a function of new episodes of depression, using generalized estimated equations. MEASUREMENTS AND MAIN RESULTS: Our primary outcome was adherence to COPD maintenance medications, measured as proportion of days covered. The exposure measure was depression. Both COPD and depression were assessed using diagnostic codes in Part A and B data. Covariates included sociodemographics, as well as clinical markers, including comorbidities, COPD severity, and depression severity. Of 31,033 beneficiaries meeting inclusion criteria, 6,227 (20%) were diagnosed with depression after COPD diagnosis. Average monthly adherence to COPD maintenance medications was low, peaking at 57% in the month after first fill and decreasing to 35% within 6 months. In our adjusted regression model, depression was associated with decreased adherence to COPD maintenance medications (odds ratio, 0.93; 95% confidence interval, 0.89-0.98). CONCLUSIONS: New episodes of depression decreased adherence to maintenance medications used to manage COPD among older adults. Clinicians who treat older adults with COPD should be aware of the development of depression, especially during the first 6 months after COPD diagnosis, and monitor patients' adherence to prescribed COPD medications to ensure best clinical outcomes.