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

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. 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). 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. 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). 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. In the LRM excluding the PDC, Hispanic ethnicity was positively associated with HbA1c level (β = 0.31, p = < 0.001). In the LRM model including PDC, PDC was negatively associated with HbA1c level (β = − 0.18, p = < 0.001). However, the positive relationship between Hispanic ethnicity and HbA1c level did not change (β = 0.31, p = < 0.001). The findings of this study suggest that the relationship between Hispanic ethnicity, HbA1c level, and factors outside of medication adherence should be explored among primary care patients receiving care in Academic Medical Centers.