Association of glycated hemoglobin with hemoglobin levels in elderly nondiabetic subjects

Background Glycated hemoglobin (HgbA1C) is being increasingly used for the diagnosis of diabetes mellitus due to its high availability and reproducibility. Several studies have shown that HgbA1C levels may be affected by levels of hemoglobin and nutritional factors associated with anemia, such as vitamin B12 and iron deficiency. However, none included elderly subjects. The aim of the present study was to investigate these effects in the older nondiabetic population. Methods A retrospective cohort study design was used. The computerized database of a large health management organization was reviewed for all subjects without diabetes mellitus who underwent at least one measurement of HgbA1C and other hemoglobin parameters in 2002 at age ≥ 65 years. HgbA1C levels were correlated with hemoglobin, hematocrit, ferritin, iron, transferrin, vitamin B12, and folic acid levels. Results A total of 11,352 subjects met the study criteria. Those with HgbA1C levels in the highest quintile (6.21–6.49%, 44.4–47.7 mmol/mol) had significantly lower levels of hemoglobin, hematocrit, and iron than patients with HgbA1C levels in the lowest quintile (< 5.4%, 36 mmol/mol), but no linear correlation was found. There was no correlation of HgbA1C level with levels of ferritin, vitamin B12, and folic acid. Conclusions In elderly nondiabetic subjects, HgbA1C levels are not correlated with hemoglobin level or nutritional factors associated with anemia and may be interpreted without consideration of these factors.