Product Director, HEOR at Boehringer-Ingelheim Pharmaceuticals

Dissertation Title

Impact of Medicare Part D coverage gap on Medicare beneficiaries with COPD: Adherence, healthcare resource use, and cost

Dissertation Abstract

Medicare Part D provides prescription drug coverage for beneficiaries to support their pharmacological treatment; however, the complex deductible structure within benefit plans creates a major coverage gap and unexpected consequences. Some evidence has demonstrated reduced adherence resulting from the coverage gap; however, little research has evaluated the effect on healthcare resource use (HRU) and cost, and no studies have been conducted for beneficiaries with chronic obstructive pulmonary disease (COPD). This study examined the impact of the coverage gap on medication adherence as well as healthcare resource use and medical cost among beneficiaries with COPD.

Claims data based on a 5% random sample of Medicare beneficiaries were used in this retrospective cohort study. For each year from 2007 to 2010, beneficiaries diagnosed with COPD were assigned to either an exposure cohort if they were at risk of the coverage gap or a control cohort if they were not.

Exposure and control cohorts were matched using a high-dimensional propensity scores. Adherence was defined as no less than 80% of the proportion of days covered (PDC) by long-acting bronchodilators (LABDs). HRU included medical encounters occurring in all care settings.

Cost included non-drug cost paid by Medicare. All outcomes were estimated at the calendar year level. Multivariable logistic and generalized linear model (GLM) regressions controlling for unbalanced covariates post-matching were applied with generalized estimating equation technique to correct for potential correlation between repeated observations of the same beneficiary. The final exposure and control cohorts each included 4,147 patient-year observations.

The results showed that the coverage gap was associated with lower adherence. Both positive and negative associations with HRU were found, but no significant difference in cost was observed between two cohorts.

This is the first study assessing the effect of the coverage gap on patients with COPD. The findings provide support for phasing out the coverage gap by 2020. More generally, the findings highlight opportunities to design benefit offerings that can improve beneficiaries' access to healthcare in ways that can impact healthcare quality and utilization.