Automated Overnight Closed-Loop Glucose Control in Young Children with Type 1 Diabetes

Background: We evaluated the effectiveness of automated overnight closed-loop (AOCL) insulin delivery and the influence of timing of initiation on glucose control overnight in young children with type 1 diabetes (T1D). Methods: Eight children with T1D (four boys, four girls) (mean +/- SD: 9.4 +/- 2.7 years old; body mass index, 18.3 +/- 2.3 kg/m(2); duration of diabetes, 3.9 +/- 2.5years; total daily insulin dose, 0.7 +/- 0.1 U/kg/day; glycosylated hemoglobin, 7.9 +/- 0.9%) were studied in a clinical research facility on two separate occasions. Subjects had a meal at 18: 00 (77 +/- 8 g of carbohydrate [CHO]) and snack at 21: 00 (21 +/- 6 g of CHO), both accompanied by a prandial insulin bolus. In random order, AOCL was started at 18: 00 or 21: 00 h and ran until 08: 00 h the next day. Subcutaneous continuous glucose monitoring data were fed automatically into the model predictive control algorithm. Calculated subcutaneous insulin infusion rates were sent wirelessly to an insulin pump. Plasma glucose was measured to assess closed-loop performance. Results: No rescue CHOs were administered. Time spent with plasma glucose in the target range from 3.9 to 8.0 mmol/L was 50.7% (29.0%, 72.2%), and it did not differ on the two occasions: median (interquartile range), 42% (18%, 64%) versus 58% (32%, 79%) (P = 0.161). Time when plasma glucose was above 8.0 mmol/L (42% [25%, 82%] vs. 29% [14%, 64%], P = 0.093), time below 3.9 mmol/L (0% [0%, 11%] vs. 8% [0%, 17%], P = 0.500), low blood glucose index (0.1 [0.0, 2.5] vs. 1.7 [0.4, 3.3], P = 0.380), plasma glucose at the start of AOCL (12.5 +/- 2.7 vs. 11.6 +/- 4.2 mmol/L, P = 0.562), and mean overnight plasma glucose (8.3 +/- 2.1 vs. 7.5 +/- 2.2 mmol/L, P = 0.246) were also similar. Conclusions: AOCL is feasible in young children with T1D. Comparable results were obtained when closed-loop was initiated at 18:00 or 21:00 h.