Exploring the Relationship Between Medication Adherence and Diabetes Disparities among Hispanic Patients in a Large Health System

BACKGROUND: Sub-optimal HbA1c control is a driver of disparities in diabetes outcomes among Hispanic patients. Differences in medication adherence may underlie racial/ethnic differences in HbA1c level. OBJECTIVE: To examine the relationship between medication adherence and disparities in HbA1c level among Hispanic patients, relative to other racial/ethnic groups, obtaining care in the University of California Health System (UC Health). DESIGN: This study used clinical, administrative, and prescription dispensing data (January-December 2021) derived from the electronic health records of 5 Academic Medical Centers in UC Health, and linear regression models (LRMs) to conduct a cross-sectional analysis of the association between medication adherence, race/ ethnicity, and HbA1c level. Adjusted LRMs were run with and without the measure of medication adherence to assess this relationship. PARTICIPANTS: Patients with a UC Health primary care physician (PCP), with >= 1 PCP visit within the last 3 years, ages 18-75, reporting Asian, Hispanic, or White race/ethnicity, and who had >= 2 encounters with an ICD diagnosis of diabetes or had a prescription for a diabetes medication within the last 2 years, as of 12/31/21 (N = 27, 542; Asian = 6253, Hispanic = 7216, White = 14,073). MAIN MEASURES: Our measure of medication adherence was the proportion of days covered (PDC) for diabetes medications in 2021. Our outcome was the most recent HbA1c value. KEY RESULTS: In the LRM excluding the PDC, Hispanic ethnicity was positively associated with HbA1c level ((3 = 0.31, p = < 0.001). In the LRM model including PDC, PDC was negatively associated with HbA1c level ((3 = - 0.18, p = < 0.001). However, the positive relationship between Hispanic ethnicity and HbA1c level did not change ((3 = 0.31, p = < 0.001). CONCLUSIONS: The findings of this study suggest that the relationship between Hispanic ethnicity, HbA1c level, and factors outside of medication adherence