Twenty‐four‐hour variations in blood glucose level in Japanese type 2 diabetes patients based on continuous glucose monitoring

Aims/Introduction High fluctuations in blood glucose are associated with various complications. The correlation between glycated hemoglobin (HbA1c) level and fluctuations in blood glucose level has not been studied in Japanese patients with type 2 diabetes. In the present study, blood glucose profile stratified by HbA1c level was evaluated by continuous glucose monitoring ( CGM ) in Japanese type 2 diabetes patients. Materials and Methods Our retrospective study included 294 patients with type 2 diabetes who were divided by HbA1c level into five groups (≥6.0 to <7.0%, ≥7.0 to <8.0%, ≥8.0 to <9.0%, ≥9.0 to <10.0% and ≥10%). The correlation between HbA1c level and CGM data was analyzed. The primary end‐point was the difference in blood glucose fluctuations among the HbA1c groups. Results The mean blood glucose level increased significantly with increasing HbA1c ( P trend  < 0.01). The standard deviation increased with increases in HbA1c ( P trend  < 0.01). The mean amplitude of glycemic excursions did not vary significantly with HbA1c. The levels of maximum blood glucose, minimum blood glucose, each preprandial blood glucose, each postprandial maximum blood glucose, range of increase in postprandial glucose from pre‐meal to after breakfast, the area under the blood concentration–time curve >180 mg/ dL and percentage of the area under the blood concentration–time curve >180 mg/ dL were higher with higher HbA1c. Mean glucose level and pre‐breakfast blood glucose level were significant and independent determinants of HbA1c. Conclusions In Japanese patients treated for type 2 diabetes, the mean amplitude of glycemic excursions did not correlate with HbA1c, making it difficult to assess blood glucose fluctuations using HbA1c. Parameters other than HbA1c are required to evaluate fluctuations in blood glucose level in patients receiving treatment for type 2 diabetes.