Impact of fasting and postprandial glycemia on overall glycemic control in type 2 diabetes: Importance of postprandial glycemia to achieve target HbA1c levels

Abstract

Objective HbA1c values reflect overall glycemic exposure over the past 2–3 months and are determined by both fasting (FPG) and postprandial plasma glucose (PPG) levels. Cross-sectional studies suggest that attainment of HbA1c goals requires specific targeting of postprandial hyperglycemia. Research design and methods We undertook a prospective intervention trial to assess the relative contribution of controlling FPG and PPG for achieving recommended HbA1c goals. One hundred and sixty-four patients (90 male and 74 female) with unsatisfactory glycemic control (HbA1c ≥7.5%) were enrolled in an individualized forced titration intensified treatment program. Results After 3 months HbA1c levels decreased from 8.7 ± 0.1 to 6.5 ± 0.1% ( p < 0.001); FPG decreased from 174 ± 4 to 117 ± 2 mg/dl ( p < 0.001); PPG decreased from 224 ± 4 to 159 ± 3 mg/dl ( p < 0.001) and daylong hyperglycemia (average of premeal, postprandial and bedtime plasma glucose excluding FPG) decreased from 199 ± 4 to 141 ± 2 mg/dl ( p < 0.0001). Patients’ weight remained unchanged (84.0 ± 1.4 kg versus 82.9 ± 1.5 kg, p = 0.36). No severe hypoglycemia occurred. Only 64% of patients achieving FPG targets of <100 mg/dl achieved an HbA1c target of <7% whereas 94% of patients achieving the postprandial target of <140 mg/dl did. Decreases in PPG accounted for nearly twice as much for the decreases in HbA1c as did decreases in FPG. PPG accounted ∼80% of HbA1c when HbA1c was <6.2% and only about 40% when HbA1c was above 9.0%. Conclusions Control of fasting hyperglycemia is necessary but usually insufficient for achieving HbA1c goals <7%. Control of postprandial hyperglycemia is essential for achieving recommended HbA1c goals.