We generated weighted and smoothed histograms (kernel density estimator) to compare the distribution of A1C in individuals with normal fasting glucose, IFG, and undiagnosed diabetes.įor the purposes of this study, we defined “elevated A1C” as A1C >6% in this population without a history of diabetes. Analyses of FPG categories were limited to the morning plasma glucose sample and corresponding 8-year fasting subsample weights were used for these analyses. SEs for all estimates were obtained using the Taylor series (linearization) method following NCHS-recommended procedures ( 16). Smoking status was determined using answers to the questions, “Have you smoked at least 100 cigarettes in your life?” and “Do you now smoke cigarettes?” Alcohol consumption was determined during the computer-assisted personal interview using answers to the questions, “In any one year, have you had at least 12 drinks of any type of alcoholic beverage?” and “In your entire life, have you had at least 12 drinks of any type of alcoholic beverage?” Detailed information regarding the collection of data in NHANES is available elsewhere ( 12).Īnalyses were performed incorporating the sampling weights (8-year combined weights) to obtain unbiased estimates from the complex NHANES sampling design using StataSE (version 10.0 StataCorporation, College Station, TX) and R (version 2 Free Software Foundation, Boston, MA). A history of cardiovascular disease was defined on the basis of a self-reported history of coronary heart disease, angina, previous heart attack, or stroke. Information on age, sex, race/ethnicity, education level, and smoking was based on self-report during the questionnaire portion of the survey. C-reactive protein was measured by latex-enhanced nephelometry, a high-sensitivity assay. Hypercholesterolemia was defined as a total cholesterol level of ≥240 mg/dl or lipid medication use. Total cholesterol was measured enzymatically. Hypertension was defined as a mean systolic blood pressure of ≥140 mmHg, a mean diastolic blood pressure of ≥90 mmHg, or hypertension medication use. The NHANES examination included measurement of height, weight, and blood pressure. and 2) A1C levels would be associated with risk factors for type 2 diabetes and its complications even in the absence of elevated glucose levels. In these studies, A1C values well within in the “normal” range (i.e., A1C 6%) are common in the general population of nondiabetic adults in the U.S. Epidemiological studies have shown that A1C values in nondiabetic adults predict incident diabetes ( 1 – 5), cardiovascular disease morbidity and mortality ( 6 – 10), and total mortality ( 7). A1C is an integrated measure of circulating glucose levels and tracks well in individuals over time.
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