Association between iron deficiency and A1C Levels among adults without diabetes in the National Health and Nutrition Examination Survey, 1999-2006

Abstract

Objective: Iron deficiency has been reported to elevate A1C levels apart from glycemia. We examined the influence of iron deficiency on A1C distribution among adults without diabetes.

Research design and methods: Participants included adults without self-reported diabetes or chronic kidney disease in the National Health and Nutrition Examination Survey 1999-2006 who were aged > or =18 years of age and had complete blood counts, iron studies, and A1C levels. Iron deficiency was defined as at least two abnormalities including free erythrocyte protoporphyrin >70 microg/dl erythrocytes, transferrin saturation <16%, or serum ferritin < or =15 microg/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. Whereas 316 women with iron deficiency had A1C > or =5.5%, only 32 women with iron deficiency had A1C > or =6.5%. Among men (n = 3,869), only 13 had iron deficiency and A1C > or =5.5%, and only 1 had iron deficiency and A1C > or =6.5%. Among women, iron deficiency was associated with a greater odds of A1C > or =5.5% (odds ratio 1.39 [95% CI 1.11-1.73]) after adjustment for age, race/ethnicity, and waist circumference but not with a greater odds of A1C > or =6.5% (0.79 [0.33-1.85]).

Conclusions: Iron deficiency is common among women and is associated with shifts in A1C distribution from <5.5 to > or =5.5%. Further research is needed to examine whether iron deficiency is associated with shifts at higher A1C levels.