Usefulness of hemoglobin A1c as a criterion of dysglycemia in the definition of metabolic syndrome in Koreans.

To explore the utility of the HbA1c criterion in the definition of metabolic syndrome (MS) in Koreans, we cross-sectionally analyzed clinical and laboratory data on 11,293 non-diabetic Korean adults (aged 20-89 years, 34% women) collected during regular health checkups. Dysglycemia was defined as either fasting plasma glucose (FPG) ≥ 5.6 mmol/l or HbA1c ≥ 5.7%. The prevalence of MS as judged by the HbA1c criterion alone (17.8%) was significantly less than that determined by FPG level alone (24.5%). Use of a combination of both criteria slightly increased the prevalence of MS (26.0%). Among the 2953 subjects categorized as having MS using the combined criteria, 929 (31%) were diagnosed by the FPG criterion alone, 177 (6%) by the HbA1c criterion alone, and 1847 (63%) using both criteria. The group diagnosed using FPG values alone had significantly higher BMI, waist circumference, blood pressure, fasting plasma insulin levels, and insulin resistance index compared with those in the group diagnosed using HbA1c levels alone. In men, the brachial-ankle pulse wave velocity was significantly higher and the HDL-cholesterol level was lower in the HbA1c-alone group. Therefore, employment of the HbA1c criterion may be useful to define MS in subjects at increased risk for atherosclerosis.