366-P: Mean Blood Glucose–Independent Racial Disparity in HbA1c and Higher Risk for Severe Hypoglycemia Is Evident among Participants in the Diabetes Control and Complications Trial

Introduction: HbA1c target levels are often used as a treatment goal for patients with diabetes. Many recent studies indicate that HbA1c overestimates mean blood glucose (MBG) among Non-Hispanic Black (NHB) patients compared to Non-Hispanic White (NHW). We hypothesized that this disparity could be associated with greater risk of hypoglycemia in NHB patients especially where management is primarily based on a treat to HbA1c target. To assess this possibility we analyzed multiyear repeated-measures data from the Diabetes Control and Complications Trial (DCCT).

Methods: Publicly available DCCT data was analyzed using mixed effects general linear modeling to evaluate the differences in HbA1c vs MBG for NWB (n=29) and NHW (n=1391) patients accounting for within patient correlation of HbA1c as well as MBG across multiple assessments. The model also controlled for age, diabetes duration, visit year and quarter, body mass index, study group and stratum. as well as interactive and nonlinear effects. Risk for severe hypoglycemia by ethnicity was separately determined.

Results: Over the course of the DCCT, NHB pts had higher HbA1c than NHW patients at any given level of MBG, with greatest difference at lower MBG levels (p=0.001). The difference between groups in HbA1c by MBG adjusted for covariables was 0.51 at MBG of 150 mg/dl (p<0.03) and 0.39 at MBG of 450 mg/dl (p=0.09) Severe hypoglycemia increased with decreasing HbA1c. Relative risk for severe hypoglycemia for NHB was 1.92 compared to NHW (p=0.02).

Conclusions: Among patients in the DCCT, HbA1c overpredicted MBG among NHB and was associated with greater risk for severe hypoglycemia. Predominant reliance on target HbA1c for management of diabetes may contribute to higher risk for hypoglycemia among NHB patients.