No Racial Differences in the Association of Glycated Hemoglobin With Kidney Disease and Cardiovascular Outcomes

OBJECTIVE: There is debate regarding the clinical significance of well-established racial differences in HbA(1c). We compared the associations of diabetes diagnostic categories for HbA(1c) and fasting glucose with clinical outcomes in black and white persons in the community. RESEARCH DESIGN AND METHODS: We conducted a prospective cohort analysis of participants without diabetes or cardiovascular disease from the Atherosclerosis Risk in Communities study. We examined the associations of clinical categories of HbA(1c) (<5.7%, 5.7–6.4%, ≥6.5%) and fasting glucose (<100, 100–125, ≥126 mg/dL) with outcomes separately among 2,484 black and 8,593 white participants and tested for race interactions. RESULTS: Baseline characteristics differed significantly in blacks compared with whites, including HbA(1c) (5.8 vs. 5.4%; P < 0.001). During 18 years of follow-up, there were trends of increased risk of kidney disease, fatal and nonfatal coronary heart disease, and stroke across categories of HbA(1c) in both blacks and whites. The adjusted hazard ratios for each outcome across categories of HbA(1c) were similar in blacks and whites (P for interaction >0.05) except for all-cause mortality. Patterns of association were similar, but weaker, for fasting glucose. HbA(1c) and fasting glucose both were more strongly associated with all-cause mortality in whites compared with blacks, largely explained by racial differences in the rate of cardiovascular deaths. CONCLUSIONS: HbA(1c) is a risk factor for vascular outcomes and mortality in both black and white adults. Patterns of association for HbA(1c) were similar to or stronger than those for fasting glucose. With respect to long-term outcomes, our findings support a similar interpretation of HbA(1c) in blacks and whites for diagnosis and treatment of diabetes mellitus.