Association Between Time in Range and HbA1c in Japanese Patients With Type 2 Diabetes Mellitus

There are no large-scale studies on the association between time in range (TIR) and hemoglobin A1c (HbA1c) in Japanese patients with type 2 diabetes mellitus (T2DM) only. The aim of this study was to define the relationship between TIR and HbA1c levels in Japanese patients with T2DM. The glycemic profile of 999 patients was analyzed with FreeStyle Libre Pro Continuous Glucose Monitoring (FLP-CGM) while they continued their prescribed glucose-lowering medications. FLP-CGM data recorded over 8 consecutive days were analyzed. The regression model for HbA1c on TIR was HbA1c = 9.4966 − 0.0309×TIR. The predicted HbA1c level for TIR of 70% was 7.33%, and is higher than recent reports subjecting mostly T1DM. The TIR corresponding to HbA1c 7.0% was 80.64%. HbA1c level correlated significantly with many FLP-CGM-derived metrics. The patients with low TIR tended to have long history of diabetes, on higher daily insulin dose and had high body mass index, HbA1c, liver dysfunction and triglyceride. Furthermore, relatively higher percentages of patients of this group used sulfonylureas, glinides, glucagon like peptide-1 receptor agonists and insulin. Our data showed that the predicted HbA1c corresponding to TIR is largely depends on the study population, thus is not uniform. Our results provide new insights on the management of T2DM.