Has Medicare Part D Reduced Racial/Ethnic Disparities in Prescription Drug Use and Spending?


  • Elham Mahmoudi,

    Corresponding author
    1. Department of Physical Medicine & Rehabilitation, University of Michigan, Ann Arbor
    • Address correspondence to Elham Mahmoudi, Ph.D., Postdoctoral Fellow, Department of Physical Medicine & Rehabilitation, University of Michigan, 325 E. Eisenhower, Suite 100, Ann Arbor, MI 48108; e-mail: Mahmoudi@med.umich.edu.

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  • Gail A. Jensen

    1. Institute of Gerontology, Wayne State University, Detroit, MI
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To evaluate whether Medicare Part D has reduced racial/ethnic disparities in prescription drug utilization and spending.


Nationally representative data on white, African American, and Hispanic Medicare seniors from the 2002–2009 Medical Expenditure Panel Survey are analyzed. Five measures are examined: filling any prescriptions during the year, the number of prescriptions filled, total annual prescription spending, annual out-of-pocket prescription spending, and average copay level.

Study Design

We apply the Institute of Medicine's definition of a racial/ethnic disparity and adopt a difference-in-difference-in-differences (DDD) estimator using a multivariate regression framework. The treatment group consists of Medicare seniors, the comparison group, adults without Medicare aged 55–63 years.

Principal Findings

Difference-in-difference-in-differences estimates suggest that for African Americans Part D increased the disparity in annual spending on prescription drugs by $258 (p = .011), yet had no effect on other measures of prescription drug disparities. For Hispanics, DDD estimates suggest that the program reduced the disparities in annual number of prescriptions filled, annual total and out-of-pocket spending on prescription drugs by 2.9 (p = .077), $282 (p = .019) and $143 (p < .001), respectively.


Medicare Part D had mixed effects. Although it reduced Hispanic/white disparities related to prescription drugs among seniors, it increased the African American/white disparity in total annual spending on prescription drugs.