An analysis combining 11 separate research studies found that blacks with diabetes have poorer control of blood sugar than whites, according to researchers from Wake Forest University School of Medicine and colleagues.

“This lower level of control may partly explain why blacks have disproportionately higher rates of death and complications from diabetes,” said Julienne Kirk, PharmD, lead author of the study published on-line today (Aug. 25) in Diabetes Care.

Kirk said the findings point to the need to determine why the difference in control exists and to identify ways to prevent or reduce the resulting health problems. Poor blood sugar control can result in long-term complications such as blindness, amputation and end-stage kidney failure.

The researchers analyzed studies that measured sugar control among blacks and whites using a blood test for glycosylated hemoglobin -  hemoglobin that has linked with glucose, or blood sugar. The lower the amounts of glycosylated hemoglobin, also called A1C, in the blood, the better the body is controlling blood sugar.

By combining the data from the 11 studies into a “meta-analysis” involving a total of 42,273 white and 14,670 black patients, they were able to detect differences that may not have shown up in each individual study. This was the first meta-analysis of racial and ethnic differences in blood sugar control among patients with diabetes.

Most of the studies included patients over age 50 with type 2 diabetes, the most common form of diabetes in which the body does not produce enough insulin or cells ignore the insulin. As a result, glucose, or sugar, builds up in the bloodstream.

The analysis focused on studies between 1993 and 2005 because the A1C measurement became more standardized during that time. Measuring A1C provides information about average blood sugar control for the previous three months and gives health care providers and patients a good idea of well how their diabetes treatment plan is working.

The researchers found that whites had about 0.65 percent less A1C than blacks. Previous research has shown that for every 1 percent reduction in A1C, there is a 21 percent reduction in any complication of diabetes. So whites in this study had a risk of complications that was 15 percent lower than blacks.

Previous studies have suggested that blood sugar control may be poorer among minority populations. Possible reasons include differences in quality of care, including the intensity of treatment; socioeconomic differences, such as being less likely to have prescription drug coverage, and genetic differences. The researchers were not able to examine these factors in their study, and said additional research is needed.

“Although A1C control among blacks likely contributes to their elevated risk of complications, it accounts for only a portion,” said Kirk, an associate professor of family and community medicine. “We need to understand more fully why this disparity exists and to eliminate factors that may be changeable, such as improving access to care.”

Funders of the research included the Centers for Disease Control and Prevention and the Association of Teachers of Preventive Medicine.

Kirk’s co-researchers were Ralph B. D’Agostino Jr., Ph.D., Ronny Bell, Ph.D., Leah Passmore, M.S., and Denise Bonds., M.D., M.P.H., all with Wake Forest, Andrew Karter, Ph.D., with Kaiser Permanente in Oakland, Calif., and K.M. Venkat Narayan, M.D., M.P.H., M.B.A., previously with the National Center for Chronic Disease Prevention and Health Promotion and now at Emory University in Atlanta, Ga.

Wake Forest University Baptist Medical Center