Significance of "Time below Range" as a Glycemic Marker Derived from Continuous Glucose Monitoring in Japanese Children and Adolescents with Type 1 Diabetes.

INTRODUCTION: We evaluated the frequencies of various glycemic markers derived from continuous glucose monitoring in Japanese children and adolescents with type 1 diabetes and assessed the significance of hypoglycemia duration. METHODS: We enrolled 85 children and adolescents (36 boys and 49 girls) with type 1 diabetes who used FreeStyle® Libre in the present study. Frequencies of blood glucose levels as time within target range (TIR; 70-180 mg/dL), time below target range (TBR; <70 mg/dL), time below extreme hypoglycemia range (TBER; <54 mg/dL), and time above range (TAR; >180 mg/dL) were assessed during a 3-month study period. Furthermore, we evaluated the intraday frequencies of TBR and TBER. RESULTS: The mean frequencies of TIR, TBR, and TAR were 52.7 ± 11.3%, 10.8 ± 5.4%, and 36.5 ± 10.8%, respectively, whereas the mean frequency of TBER was 1.1 ± 0.9% (0-3.0%); there was no clinical episode of severe hypoglycemia. The mean frequency of TBR was significantly greater in 0-6 h (16.9 ± 5.2%) than in 6-12 h (7.8 ± 2.9%) and 18-24 h (6.8 ± 4.8%; p < 0.01) time zones, respectively. DISCUSSION/CONCLUSION: We found similar TIR and comparatively higher TBR frequencies, particularly during sleep, than those that were previously reported. Possible reasons for the higher frequency of TBR include differences in the quality of insulin treatment and diabetes care between the present study and the European studies. The utilization of advanced technologies, such as a predictive low-glucose suspend-function pump or closed-loop therapy, can reduce the frequency of TBR, with a consequent increase in TIR frequency and comprehensive improvement in glycemic control.