Association of chronic obstructive pulmonary disease maintenance medication adherence with all-cause hospitalization and spending in a Medicare population.

BACKGROUND: Although maintenance medications are a cornerstone of chronic obstructive pulmonary disease (COPD) management, adherence remains suboptimal. Poor medication adherence is implicated in poor outcomes with other chronic conditions; however, little is understood regarding links between adherence and outcomes in COPD patients.
OBJECTIVE: This study investigates the association of COPD maintenance medication adherence with hospitalization and health care spending.
METHODS: Using the 2006 to 2007 Chronic Condition Warehouse administrative data, this retrospective cross-sectional study included 33,816 Medicare beneficiaries diagnosed with COPD who received at least 2 prescriptions for ≥1 COPD maintenance medications. After a 6-month baseline period (January 1, 2006 to June 30, 2006), beneficiaries were followed through to December 31, 2007 or death. Two medication adherence measures were assessed: medication continuity and proportion of days covered (PDC). PDC values ranged from 0 to 1 and were calculated as the number of days with any COPD maintenance medication divided by duration of therapy with these agents. The association of adherence with all-cause hospital events and Medicare spending were estimated using negative binomial and γ generalized linear models, respectively, adjusting for sociodemographics, Social Security disability insurance status, low-income subsidy status, comorbidities, and proxy measures of disease severity.
RESULTS: Improved adherence using both measures was significantly associated with reduced rate of all-cause hospitalization and lower Medicare spending. Patients who continued with their medications had lower hospitalization rates (relative rate [RR] = 0.88) and lower Medicare spending (-$3764), compared with patients who discontinued medications. Similarly, patients with PDC ≥0.80 exhibited lower hospitalization rates (RR = 0.90) and decreased spending (-$2185), compared with patients with PDC <0.80.
CONCLUSIONS: COPD patients with higher adherence to prescribed regimens experienced fewer hospitalizations and lower Medicare costs than those who exhibited lower adherence behaviors. Findings suggested the clinical and economic importance of medication adherence in the management of COPD patients in the Medicare population.