Association between adherence to medications for COPD and medications for other chronic conditions in COPD patients

BACKGROUND: Patients with COPD often have multiple comorbidities requiring use of multiple medications, and adherence rates for maintenance COPD (mCOPD) medications are already known to be suboptimal. Presence of comorbidities in COPD patients, and use of medications used to treat those comorbidities (non-COPD medications), may have an adverse impact on adherence to mCOPD medications. OBJECTIVE: The objective of the study was to evaluate the association between non-adherence to mCOPD medications and non-COPD medications in COPD patients. METHODS: COPD patients were identified using a large administrative claims database. Selected patients were 40–89 years old and continuously enrolled for 12 months prior to and 24 months after the first identified COPD diagnosis (index date) during January 1, 2009 to December 31, 2010. Patients were required to have ≥1 prescription for a mCOPD medication within 365 days of the index date and ≥1 prescription for one of 12 non-COPD medication classes within ±30 days of the first COPD prescription. Adherence (proportion of days covered [PDC]) was measured during 365 days following the first COPD prescription. The association between non-adherence (PDC <0.8) to mCOPD and non-adherence to non-COPD medications was determined using logistic regression, controlling for baseline patient characteristics. RESULTS: A total of 14,117 patients, with a mean age of 69.9 years, met study criteria. Of these, 40.9% were males and 79.2% were non-adherent to mCOPD medications with a mean PDC of 0.47. Non-adherence to mCOPD medications was associated with non-adherence to 10 of 12 non-COPD medication classes (odds ratio 1.38–1.78, all P<0.01). CONCLUSION: Adherence to mCOPD medications is low. Non-adherence (or adherence) to mCOPD medications is positively related to non-adherence (or adherence) to non-COPD medications, implying that the need to take medications prescribed for comorbid conditions does not adversely impact adherence to mCOPD medications.