Abstract

Objective: Iron deficiency has been reported to elevate hemoglobin A1c (HbA1c) levels apart from glycemia. We examined the influence of iron deficiency on HbA1c distribution among adults without diabetes.

Research Design and Methods: Participants included adults without self-reported diabetes or chronic kidney disease in NHANES 1999-2006 who were aged ≥ 18 years of age and had complete blood counts, iron studies, and HbA1c levels. Iron deficiency was defined as at least 2 abnormalities including: free erythrocyte protoporphyrin > 70 ug/dl red blood cells, transferrin saturation < 16%, or serum ferritin ≤ 15 ug/L. Anemia was defined as hemoglobin < 13.5 g/dl in men and < 12.0 g/dl in women.

Results: Among women (n=6,666), 13.7% had iron deficiency and 4.0% had iron deficiency anemia. While 316 women with iron deficiency had Hba1c >=5.5%, only 32 women with iron deficiency had Hba1c >=6.5%. Among men (n=3,869), only 13 had iron deficiency and an HbA1c >=5.5% and only 1 had iron deficiency and an HbA1c > 6.5%. Among women, iron deficiency was associated with a greater odds of HbA1c >= 5.5% (OR 1.39, 95% CI, 1.11, 1.73) after adjustment for age, race/ethnicity, and waist circumference, but not with a greater odds of HbA1c >= 6.5% (OR 0.79, 95% CI 0.33, 1.85).

Conclusions: Iron deficiency is common among women and is associated with shifts in HbA1c distribution from an HbA1c < 5.5% to > 5.5%. Further research is needed to examine whether iron deficiency is associated with shifts at higher HbA1c levels.