Glycated hemoglobin, diabetes, and cardiovascular risk in nondiabetic adults

Abstract

Background: Fasting glucose is the standard measure used to diagnose diabetes in the United States. Recently, glycated hemoglobin was also recommended for this purpose.

Methods: We compared the prognostic value of glycated hemoglobin and fasting glucose for identifying adults at risk for diabetes or cardiovascular disease. We measured glycated hemoglobin in whole-blood samples from 11,092 black or white adults who did not have a history of diabetes or cardiovascular disease and who attended the second visit (occurring in the 1990-1992 period) of the Atherosclerosis Risk in Communities (ARIC) study.

Results: The glycated hemoglobin value at baseline was associated with newly diagnosed diabetes and cardiovascular outcomes. For glycated hemoglobin values of less than 5.0%, 5.0 to less than 5.5%, 5.5 to less than 6.0%, 6.0 to less than 6.5%, and 6.5% or greater, the multivariable-adjusted hazard ratios (with 95% confidence intervals) for diagnosed diabetes were 0.52 (0.40 to 0.69), 1.00 (reference), 1.86 (1.67 to 2.08), 4.48 (3.92 to 5.13), and 16.47 (14.22 to 19.08), respectively. For coronary heart disease, the hazard ratios were 0.96 (0.74 to 1.24), 1.00 (reference), 1.23 (1.07 to 1.41), 1.78 (1.48 to 2.15), and 1.95 (1.53 to 2.48), respectively. The hazard ratios for stroke were similar. In contrast, glycated hemoglobin and death from any cause were found to have a J-shaped association curve. All these associations remained significant after adjustment for the baseline fasting glucose level. The association between the fasting glucose levels and the risk of cardiovascular disease or death from any cause was not significant in models with adjustment for all covariates as well as glycated hemoglobin. For coronary heart disease, measures of risk discrimination showed significant improvement when glycated hemoglobin was added to models including fasting glucose.

Conclusions: In this community-based population of nondiabetic adults, glycated hemoglobin was similarly associated with a risk of diabetes and more strongly associated with risks of cardiovascular disease and death from any cause as compared with fasting glucose. These data add to the evidence supporting the use of glycated hemoglobin as a diagnostic test for diabetes.

Figure 1. The Incidence Rate of Self-Reported Diagnosed Diabetes in the Study Population, According to the Baseline Glycated Hemoglobin Category

The incidence rates are shown, per 1000 person-years, for the median of each glycated hemoglobin category. The I bars denote the 95% confidence intervals.

Figure 2. Adjusted Hazard Ratios for Self-Reported Diagnosed Diabetes and Coronary Heart Disease, Ischemic Stroke, and Death from Any Cause, According to the Baseline Glycated Hemoglobin Value

The hazard ratios are per each absolute increase of 1 percentage point in the glycated hemoglobin value at baseline. The shaded area is the 95% confidence interval from the restricted-cubic-spline model. Both models are centered at the median (5.4%) and the plot was truncated at the 2.5th and 97.5th percentiles of glycated hemoglobin (4.7% and 6.8%, respectively). The hazard ratios were adjusted for age, sex, and race (black or white), low-density and high-density cholesterol levels, log-transformed triglyceride level, body-mass index, waist-to-hip ratio, hypertension (yes or no), family history of diabetes (yes or no), education (less than high school, high school or equivalent, or college or above), alcohol use (currently, formerly, or never), physical-activity index score, and smoking status (current smoker, former smoker, or never smoked). The data are shown on a natural-log scale.