Effects of Part D Star Ratings on racial and ethnic disparities in health care costs

Background: Racial/ethnic minorities are less likely than non-Hispanic White (White) patients to be included in the Medicare Part D Star Ratings measure assessment due to the restrictive inclusion criteria for the measures.Objective: This paper examined the effects of racial/ethnic disparities in the measure assessment in Part D Star Ratings on disparities in healthcare costs among patients with Alzheimer's disease and related dementias (ADRD).Methods: This crosssectional study analyzed 2017 Medicare data. Proportions of Beneficiaries with ADRD were categorized into the included and excluded groups based on the inclusion criteria for the calculation of medication adherence measures in Star Ratings. Outcomes included costs for medications, physician visits, emergency room (ER) visits, and total costs. A generalized linear model was employed to compare costs across racial/ethnic groups. To explore the differential disparities in healthcare costs between the 2 groups, interaction terms between dummy variables for being excluded from the measure calculation and racial/ethnic minorities were included in the models.Results: The patterns of racial/ethnic disparities in healthcare costs found in this study were generally consistent with expectations, with some exceptions. For example, compared with White patients, in the hyperlipidemia cohort, the physician visit cost for Black patients among the included group was 31% lower (cost ratio or CR = 0.69, 95% CI = 0.67-0.72); in the hypertension cohort, the hospitalization cost for Blacks among the excluded group was 15% higher (CR = 1.15, 95% CI = 1.12-1.19). More importantly, exclusion from measurement assessments was associated with differential cost disparities. For example, compared with individuals included in the measure assessment for hypertension, the Black-White disparities in costs for hospitalization and total healthcare were 30% higher (CR = 1.30, 95% CI = 1.26-1.34), and 10% higher (CR = 1.10; 95% CI = 1.08-1.12), respectively, among the excluded group.Conclusions: Medicare Part D Star Ratings may be associated with aggravated racial/ethnic disparities in healthcare costs in the Medicare Part D population.