The Association of Red Cell Distribution Width with Glycated Hemoglobin among Healthy Adults without Diabetes Mellitus

<b><i>Background:</i></b> Red cell distribution width (RDW) and hemoglobin A1c (HbA1c) are both known to be predictive of future cardiovascular disease (CVD). <b><i>Objective:</i></b> We hypothesized that RDW would be associated with HbA1c in adults without diabetes independent of fasting blood glucose (FBG). <b><i>Methods:</i></b> This cross-sectional study included 15,343 nondiabetic adults, free of CVD, enrolled in NHANES 1999–2008. Adjusted means of RDW were calculated across HbA1c categories for the overall population. Multivariable regression analyses were performed analyzing the association between RDW and HbA1c for individuals with available data on FBG (n = 7,454). <b><i>Results:</i></b> RDW significantly correlated with HbA1c (r = 0.27, p < 0.001; n = 15,343), with a gradual increase in adjusted mean RDW across HbA1c categories (12.59% ± 0.02% in the group with HbA1c ≤4.8% vs. 12.92% ± 0.02% in the group with HbA1c >5.8%, p < 0.001 for trend). In regression analyses, RDW independently predicted HbA1c (β-coefficient 0.034, 95% CI 0.026–0.042, p < 0.001). <b><i>Conclusion:</i></b> RDW significantly predicts HbA1c independent of FBG in healthy nondiabetic adults, suggesting the possibility of chronic hyperglycemia mediating the association between RDW and CVD.