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. 2014 Feb;24(2):83-9.
doi: 10.1016/j.annepidem.2013.10.008. Epub 2013 Oct 18.

Hemoglobin A1c, Fasting Plasma Glucose, and 2-hour Plasma Glucose Distributions in U.S. Population Subgroups: NHANES 2005-2010

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Hemoglobin A1c, Fasting Plasma Glucose, and 2-hour Plasma Glucose Distributions in U.S. Population Subgroups: NHANES 2005-2010

Andy Menke et al. Ann Epidemiol. .
Free PMC article

Abstract

Purpose: Although mean concentrations of hemoglobin A1c (A1C), fasting plasma glucose, and 2-hour plasma glucose differ by demographics, it is unclear what other characteristics of the distributions may differ, such as the amount of asymmetry of the distribution (skewness) and shift left or right compared with another distribution (shift).

Methods: Using kernel density estimation, we created smoothed plots of the distributions of fasting plasma glucose (N = 7250), 2-hour plasma glucose (N = 5851), and A1C (N = 16,209) by age, race-ethnicity, and sex in the 2005-2010 National Health and Nutrition Examination Survey, a nationally representative sample of U.S. adults including people with and without diabetes. We tested differences in distributions using cumulative logistic regression.

Results: The distributions were generally unimodal and right-skewed. All distributions were shifted higher and more right-skewed for older age groups (P < .001 for each marker). Compared with non-Hispanic whites, the distribution of fasting plasma glucose was shifted higher for Mexican-Americans (P = .01), whereas the distribution of A1C was shifted higher for non-Hispanic blacks (P < .001). The distribution of fasting plasma glucose was shifted higher for men (P < .001) and the distribution of 2-hour plasma glucose was shifted higher for women (P = .01).

Conclusions: We provide a graphic reference for comparing these distributions and diabetes cut-points by demographic factors.

Keywords: 2-hour plasma glucose; Fasting plasma glucose; Hemoglobin A1c; Kernel density estimation; NHANES.

Figures

Figure 1
Figure 1
Kernel density plots of fasting plasma glucose, 2-hour plasma glucose, and A1C among the total population and after excluding participants with previously diagnosed diabetes. The vertical lines denote the American Diabetes Association cutpoints for prediabetes (5.7% [39 mmol/mol], 100 mg/dL, and 140 mg/dL) and diabetes (6.5% [48 mmol/mol], 126 mg/dL, and 200 mg/dL). Among participants without diagnosed diabetes, 38.9% had a fasting plasma glucose 100–125 mg/dL, 3.5% had a fasting plasma glucose ≥126 mg/dL, 27.4% had a 2-hour plasma glucose 140–199 mg/dL, 5.4% had a 2-hour plasma glucose ≥200 mg/dL, 20.9% had an A1C 5.7–6.4%, and 2.3% had an A1C ≥6.5%.
Figure 2
Figure 2
Kernel density plots of fasting plasma glucose, 2-hour plasma glucose, and A1C by A) age group, B) race-ethnicity, and C) sex. The vertical lines denote the American Diabetes Association cutpoints for prediabetes (5.7% [39 mmol/mol], 100 mg/dL, and 140 mg/dL) and diabetes (6.5% [48 mmol/mol], 126 mg/dL, and 200 mg/dL). Differences in distributions were tested using cumulative logistic regression as presented in Table 2.

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