Using a closed loop system significantly improves time in range (TIR) in patients with type 1 diabetes (T1D). In a 6-month RCT, 112 subjects were assigned to closed-loop control (Tandem Control-IQ) after obtaining two weeks of baseline CGM data from sensor-augmented pump therapy. We compared glycemic outcomes from baseline to end of study among subgroups classified by baseline HbA1C level. Participants’ mean age was 33±16 (range 14-71 yrs) and mean baseline HbA1C was 7.4±1.0 (range 5.4% to 10.6%). All HbA1c subgroups showed an improvement in TIR due to reduction of both hyperglycemia and hypoglycemia (Table). Those with HbA1c <6.5% improved mostly by reducing nocturnal (MN to 6 AM) hypoglycemia. Those with HbA1c ≥8.5% improved mostly by reducing daytime and nocturnal hyperglycemia. Participants with lower HbA1c at baseline reduced their overnight hypoglycemia the most, likely due to the system’s automated basal insulin adjustment. For those with higher HbA1c at baseline, increased TIR came mostly from hyperglycemia reduction, likely due to automated basal insulin adjustment in day and night. These participants likely also benefitted from hourly automatic correction boluses during the day. All HbA1c subgroups benefitted from automated insulin delivery.


L. Ekhlaspour: None. D. Raghinaru: None. J. Lum: None. S.A. Brown: Research Support; Self; Dexcom, Inc., Insulet Corporation, Roche Diabetes Care, Tandem Diabetes Care, Tolerion, Inc. B.A. Buckingham: Advisory Panel; Self; ConvaTec Inc., Medtronic. Research Support; Self; Beta Bionics, Inc., Dexcom, Inc., Insulet Corporation, Medtronic, Tandem Diabetes Care.


National Institute of Diabetes and Digestive and Kidney Diseases (UC4108483); University of Virginia; Tandem Diabetes Care

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