Gap in glycemic control between blacks, whites

Differences in medication adherence do not explain the racial disparities.

Targeting medication adherence alone is unlikely to reduce disparities in glycemic control, according to researchers from Harvard Medical School and Massachusetts General Hospital.

The researchers examined medication adherence and self-management as possible determinants of increased glycemic risk among black patients with type 2 diabetes, compared with white patients.

“Our findings suggest that improving medication adherence alone is unlikely to reduce the black — white gap in glycemic control in this setting,” they wrote. “Racial differences in glycemic control at the time of diagnosis are consistent with possible genetic or environmental drivers.”

Retrospective longitudinal study

The researchers studied 1,806 adults (467 blacks) who were new users of oral hypoglycemic therapy. All patients were followed for at least one year.

Upon initiation, black patients had higher average HbA1c values than whites — 9.8% vs. 8.9% (P<.0001). Evidence suggests that racial differences in glycemic control cannot be fully explained by variations in the site or quality of care but are perhaps due to unmeasured biological, cultural or environmental determinants, according to the study.

Black patients were less likely to adhere to their medication during the first year of therapy compared with white patients (72% vs. 78%; P<.0001).

This finding was “associated with clinically significant reductions in HbA1c for both black and white patients but was associated with only a modest reduction by the black —white gap in glycemic control,” the researchers wrote.

Additional research is required to explore possible genetic and environmental determinants of elevated HbA1c among blacks at diagnosis of diabetes, they said. – by Katie Kalvaitis

Adams et al studied 1,800 diabetic patients and found that blacks had higher HbA1c than whites, even after adjusting for a somewhat lower medication adherence rate of 72% vs. 78%. They suggest that there may be a racial propensity to poorer glycemic control, perhaps because of lower socioeconomic factors leading to worse outcome. Perhaps the authors do not recognize the alternative possibility that blacks simply have higher HbA1c levels than whites for a given level of glycemia. This surprising finding was recently reported in an analysis of ethnic difference among participants in the Diabetes Prevention Program, all with impaired glucose tolerance.

– Zachary T. Bloomgarden, MD

Endocrine Today Editorial Board member

For more information:
Adams AS, Trinacty CM, Zhang F, et al. Medication adherence and racial differences in A1c control. Diabetes Care. 2008;31:916-921.