Predictive Value of Fasting Glucose, Postload Glucose, and Hemoglobin A1c on Risk of Diabetes and Complications in Chinese Adults

Abstract

Objective: Uncertainty remains regarding the predictive value of various glycemic measures as they relate to the risk of diabetes and its complications. Using the cutoffs recommended by the American Diabetes Association's 2010 criteria, we determined the associations of fasting plasma glucose (FPG), 2-h postload glucose (2h-PG), and HbA_1c with the outcomes.

Research design and methods: Baseline medical history, FPG, 2h-PG, and HbA_1c were obtained from a population-based cohort of 193,846 adults aged ≥40 years in China during 2011-2012. A follow-up visit was conducted during 2014-2016 in order to assess incident diabetes, cardiovascular disease (CVD), cancer, and mortality.

Results: We documented 8,063 cases of diabetes, 3,014 CVD-related events, 1,624 cases of cancer, and 2,409 deaths during up to 5 years of follow-up. Multivariable-adjusted risk ratios (95% CIs) of diabetes associated with prediabetes based on FPG of 100-125 mg/dL, 2h-PG of 140-199 mg/dL, or HbA_1c of 5.7-6.4% (39-47 mmol/mol) were 1.60 (1.43-1.79), 2.72 (2.43-3.04), and 1.49 (1.36-1.62), respectively. Restricted cubic spline analyses suggested J-shaped associations of FPG, 2h-PG, and HbA_1c levels with CVD, cancer, and mortality. Multivariable-adjusted hazard ratios (95% CIs) associated with untreated diabetes based on FPG ≥126 mg/dL, 2h-PG ≥200 mg/dL, or HbA_1c ≥6.5% (48 mmol/mol) were 1.18 (1.05-1.33), 1.31 (1.18-1.45), and 1.20 (1.07-1.34) for CVD; 1.10 (0.92-1.32), 1.44 (1.25-1.67), and 1.08 (0.92-1.28) for cancer; and 1.37 (1.20-1.57), 1.57 (1.41-1.76), and 1.33 (1.17-1.52) for mortality, respectively. 2h-PG remained significantly associated with outcomes in models including FPG and HbA_1c as spline terms. Furthermore, 2h-PG significantly improved the ability of the C statistic to predict diabetes, CVD, and mortality.

Conclusions: 2h-PG remains independently predictive of outcomes in models including FPG and HbA_1c. Therefore, in addition to FPG and HbA_1c, routine testing of 2h-PG should be considered in order to better assess the risks of outcomes.