Effects of star ratings bonus payments on disparities in medication utilization issues.

Background: Previous literature suggested that the consequences of inappropriate medication use may be borne disproportionately by racial/ethnic minorities. It is, therefore, essential to examine if quality improvement initiatives, such as Medicare Part D Star Ratings (Star Ratings), can improve these disparities.

Objective: To assess the impact of Star Ratings bonus payments to Medicare Advantage prescription drug plans (MAPDs) implemented in 2012 on racial/ethnic disparities in medication utilization issues (MUIs).

Methods: This study mainly used secondary data from Medicare administrative data linked to Area Health Resources Files for years before (2010-2011) and after MAPD bonus payment implementation (2016-2017). Patients in MAPDs were treated as the intervention group, and those in independent prescription drug plans (PDPs) were used as the comparison group because PDPs were ineligible for bonuses. MUIs targeted and not targeted in Star Ratings were both examined to determine spillover effects. A difference-in-differences approach was applied by including in a logistic regression a 3-way interaction term for dummy variables for racial/ethnic minorities, later period of 2016-2017, and MAPD plan.

Results: Racial/ethnic minorities experienced more MUIs: e.g., the odds of MUIs targeted in Star Ratings among MAPD enrollees were 83% higher (odds ratio [OR] = 1.83; 95% confidence interval [CI] = 1.71-1.96) for Black than White patients. Black-White disparities in MUIs targeted in Star Ratings decreased 16% more (OR = 0.84; 95% = CI 0.78-0.91) over time among MAPD enrollees than those in PDPs. This pattern was not found for non-Star Ratings measures. Changes in Hispanic-White disparities were similar between MAPD and PDP enrollees for MUIs targeted and not-targeted by Star Ratings. Asian-White and Other-White disparities in MUIs did not experience a higher reduction among MAPD enrollees than PDP enrollees.

Conclusions: Part D bonus payments are associated with lower Black-White disparities in MUIs targeted by Star Ratings. However, Part D bonus payments may not have reduced Hispanic-White or Asian-White disparities. Future research should explore the causes of the bonus payments' heterogeneous effects across racial/ethnic groups.