Endocrine Abstracts

Hybrid closed-loop (HCL) systems combine continuous glucose monitoring (CGM) with automated insulin delivery to support glycaemic control in type 1 diabetes. This study evaluated glycaemic outcomes and behavioural factors influencing control in young adults using HCL systems at TUH and NGH. We analysed 30-day HCL data from young adults using Medtronic 780G or Tandem Control-IQ via CareLink™ and Glooko™. Metrics included CGM wear, auto mode use (AID), manual bolus frequency, and active insulin time (AIT). Glycaemic outcomes were time-in-range (TIR: 3.9-10.0 mmol/l/l/l), time-below-range (TBR <3.9 mmol/l/l), and time-above-range (TAR >10.0 mmol/l/l). An engagement score (0-4) was calculated using thresholds for AID >80%, sensor wear >80%, manual bolusing >median, and AIT <2.5 hours. Linear regression assessed associations between engagement, behaviours, and TIR. Among 61 young adults (mean age 21.3 ± 1.8 years), mean TIR was 62.8% ± 11.9%, with TBR 1.6% ± 1.6%; 90% maintained TBR <4%. Fully engaged 780G users (score = 4) achieved 70.3% TIR vs. 52.5% in the least engaged. Each 1-point increase in engagement score was associated with a 4.3% rise in TIR (P < 0.05). AID use (P = 0.003), shorter AIT (P = 0.027), and use of exercise mode (P < 0.05) were independently linked to higher TIR without increasing hypoglycaemia. Young adults using HCL pumps often fall short of glycaemic targets. However, greater engagement with pump features is strongly associated with improved glycaemic control.