The phenomenon of HbA1c stability and the risk of hypoglycemia in long-standing type 1 diabetes

Abstract

AimsHyperglycemia is the major factor underlying vascular complications of diabetes. Unfortunately, improved glycemia control is frequently accompanied by an increased risk of hypoglycemia. The aim of the study was to assess the relationship between hemoglobin A1c (HbA1c) and 1-week Continuous Glucose Monitoring (CGM) data in long-standing type 1 diabetes (T1DM). MethodsWe recruited 58 subjects with long-standing T1DM consecutively enrolled to the study. Each patient underwent a 1-week CGM and laboratory profile at baseline. Subjects were divided into three subgroups according to baseline HbA1c tertiles: T1 < 7.1%, T2 = 7.1–8.0%, and T3 > 8.0%. ResultsT1 patients were characterized by the longest time in range (66% of a week), whereas T3 patients experienced hyperglycemia in >50% time of the week. T1 patients were noted to have 25% of nighttime with glycemia <3.9 mmol/L (8% with glycemia <2.8 mmol/L). Most recent HbA1c closely reflected 10-years mean HbA1c values (R = 0.83; P < 0.0001). Conclusions(1) Long-term diabetes control (10 years HbA1c mean) is a strong predictor of the current HbA1c levels. (2) Current and historical HbA1c levels are closely linked to CGM-derived glycemia. (3) Risk of clinically significant hypoglycemia negatively correlates with HbA1c. (4) HbA1c > 8.0% is associated with unsatisfactorily low (44%) time in range.