Electronic Theses and Dissertations

Date of Award


Document Type


Degree Name

Ph.D. in Pharmaceutical Sciences

First Advisor

John P. Bentley

Second Advisor

Sujith Ramachandran

Third Advisor

Marie Barnard


University of Mississippi

Relational Format



This dissertation examined racial and ethnic disparities in: (1) the impact of the Centers for Medicare and Medicaid Services (CMS) policy and payment changes to the Medicare Part D Star Ratings Program on adherence to diabetes, renin-angiotensin system antagonists (RASA) and statin medications, (2) the spillover effect of this program onto nontargeted therapies used to treat hypertension (calcium channel blockers and beta blockers), and (3) insulin non-persistence among Medicare beneficiaries, and quantified the contribution of sociodemographic, clinical and cost factors associated with the racial and ethnic disparities.

For objectives 1 and 2, interrupted time series (ITS) analyses were conducted using 2010 to 2018 data from the Medicare 5% national sample. For objective 3, a Blinder-Oaxaca (B-O) decomposition analysis was conducted using the 2018 Medicare 20% national sample.

Results of the ITS analysis showed that the CMS policy and payment changes to the Star Ratings program have resulted in improved medication adherence not only to the three adherence measures used in the Star Ratings program (diabetes, RASA, statins), but also to nontargeted therapies used to treat hypertension, regardless of race/ethnicity. However, because baseline adherence for some minority populations (e.g., Black beneficiaries) were significantly lower than White beneficiaries, racial and ethnic disparities persist.

Results of the B-O also found significant racial and ethnic disparities in insulin non-persistence for all minority race/ethnicity groups when compared with White beneficiaries. Major contributors to racial and ethnic disparities included low income subsidy/dual eligibility status, patient out of pocket prescription cost, and social determinants of health factors.

The CMS policy and payment changes to the Star Ratings program have resulted in significant improvement in medication adherence for Medicare beneficiaries across race/ethnicity groups. However, racial and ethnic disparities remain. Payers and providers should focus interventions on equitable distribution of resources targeted at minority populations. These interventions should also seek to address social determinant of health factors, which could have the most impact on improving medication use among minority groups, as evidenced by the results of the decomposition analysis.



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