Does Genetic Ancestry Explain Higher Values of Glycated Hemoglobin in African Americans?

OBJECTIVE—Glycated hemoglobin (HbA1c) values are higher in African Americans than whites, raising the question of whether classification of diabetes status by HbA1c should differ for African Americans. We investigated the relative contribution of genetic ancestry and nongenetic factors to HbA1c values and the effect of genetic ancestry on diabetes classification by HbA1c in African Americans. RESEARCH DESIGN AND METHODS—We performed a cross-sectional analysis of data from the community-based Ath-erosclerosis Risk in Communities (ARIC) Study. We estimated percentage of European genetic ancestry (PEA) for each of the 2,294 African Americans without known diabetes using 1,350 ancestry-informative markers. HbA1c was measured from whole-blood samples and categorized using American Diabetes Associa-tion diagnostic cut points (,5.7, 5.7–6.4, and $6.5%)