Effects of Sensor-Augmented Pump Therapy on Glycemic Variability in Well-Controlled Type 1 Diabetes in the STAR 3 Study

Background: Compared with multiple daily injections (MDI), sensor-augmented pump (SAP) insulin therapy may reduce glycemic variability and oxidative stress in type 1 diabetes in a glycosylated hemoglobin (A1C)-independent manner. Subjects and Methods: The STAR 3 study compared SAP with MDI therapy for 1 year. Week-long continuous glucose monitoring studies were conducted at baseline and 1 year for assessment of glycemic variability in both groups. Soluble CD40 ligand (CD40L), a biomarker of inflammation and thrombocyte function, was measured at baseline and 1 year. Subjects were classified according to treatment group and 1-year A1C levels (<6.5%, 6.5-6.9%, 7-7.9%, >= 8%). Glycemic parameters were compared between SAP and MDI subjects in each A1C cohort. Results: At 1 year, sensor glucose values at A1C levels >= 6.5% were similar in the SAP and MDI groups. However, sensor glucose SD and coefficient of variation (CV) values were lower at A1C levels <8% among SAP than among MDI subjects; the overall between-group difference was significant for both SD (P < 0.01) and CV (P = 0.01). The overall mean amplitude of glycemic excursion was similar in MDI and SAP groups (P = 0.23). CD40L levels fell over the course of the study in both groups, but the between-group difference was not significant (P = 0.18). CD40L concentrations were unrelated to A1C, change in A1C from baseline, or glycemic variability. Conclusions: At comparable A1C levels of < 8%, SAP reduced glycemic variability as measured by SD and CV compared with MDI. SAP may provide beneficial reductions in the number and severity of glycemic excursions.