Glycemic variability modifies the relationship between time in range and hemoglobin A1c estimated from continuous glucose monitoring: A preliminary study

Abstract

Aims Although there is a linear relationship between time in range (TIR) and hemoglobin A1c (HbA1c), a great variability of calculated TIR values for a given HbA1c, and vice versa, has been reported. Whether glycemic variability accounts for part of this variability remains to be investigated.Methods The data of continuous glucose monitoring (CGM) from 2559 patients with type 2 diabetes was analyzed. Glycemic variability was assessed by glucose coefficient of variation (CV), and estimated HbA1C (eHbA1c) was calculated from mean sensor glucose.Results A strong correlation between TIR and eHbA1c (r = -0.908) was observed. The slopes of regression lines fitted to TIR values as a function of eHbA1c differed significantly for individuals with varying degrees of CV, especially when patients were stratified as stable (CV < 36%) or unstable (CV ≥ 36%) glucose levels. For patients in the high- or low-range of eHbA1c, there was a high variability of TIR values according to CV.Conclusions Glycemic variability significantly mediates the relationship between TIR and eHbA1c, and should be taken into consideration when setting an individualized target of TIR.