The relationship between waist circumference and glycated hemoglobin in the United States

Abstract

PURPOSE: Obesity leads to type 2 diabetes, an important risk factor for cardiovascular disease. As glycated hemoglobin (A1C) can now be used for the diagnosis of diabetes, we studied the relationship between A1C and waist circumference. METHODS: 1806 men and 1734 women over the age of 20 years in the United States National Health and Nutrition Examination Survey 2005-2008 who had fasted overnight and were not on medication for diabetes were included for analysis. A1C levels of 5.7% and 6.5% were used as cut-offs for pre-diabetes and diabetes respectively. RESULTS: The waist circumference had a linear association with A1C in both men (P=0.001) and women (P<0.001). An A1C level of 5.7% corresponded to a waist circumference of 98.4, 102.4 and 106.4 cm in men and 96.1, 96.6 and 97.0 cm in women at ages 30, 50 and 70 respectively. An A1C level of 6.5% corresponded to a waist circumference of 101.5, 105.4 and 109.4 cm in men and 103.4, 103.9 and 104.4 cm in women at ages 30, 50 and 70 years respectively. The waist circumference increased significantly with age in men (P<0.001) but only slightly in women. The linear relationship between waist circumference and A1C was seen in all non-Hispanic whites (men, P=0.013; women, P<0.001), non-Hispanic blacks (men, P<0.001; women, P=0.013), and Mexican American women (P=0.001). CONCLUSIONS: A1C level increases linearly with waist circumference. A smaller waist circumference corresponds to a lower A1C level in both men and women. This association is seen among all ethnic groups except Mexican American men. In men, the waist circumferences associated with pre-diabetes and diabetes change with age. Our results reveal that younger American men with a waist circumference below 100 cm are already at risk of pre-diabetes.