Hybrid Closed Loop in Adults With Type 1 Diabetes and Severely Impaired Hypoglycemia Awareness

Melissa H. Lee, Judith Gooley, Varuni Obeyesekere, Jean Lu, Barbora Paldus, Christel Hendrieckx, Richard J. MacIsaac, Sybil A. McAuley, Jane Speight, Sara Vogrin, Alicia J. Jenkins, D. Jane Holmes-Walker, David N. O’Neal, Glenn M. Ward, on behalf of the Australian JDRF Closed-Loop Research Group

Research output: Contribution to journalArticleResearchpeer-review


Background: Benefits of hybrid closed-loop (HCL) systems in a high-risk group with type 1 diabetes and impaired awareness of hypoglycemia (IAH) have not been well-explored. Methods: Adults with Edmonton HYPO scores ≥1047 were randomized to 26-weeks HCL (MiniMed™ 670G) vs standard therapy (multiple daily injections or insulin pump) without continuous glucose monitoring (CGM) (control). Primary outcome was percentage CGM time-in-range (TIR; 70-180 mg/dL) at 23 to 26 weeks post-randomization. Major secondary endpoints included magnitude of change in counter-regulatory hormones and autonomic symptom responses to hypoglycemia at 26-weeks post-randomization. A post hoc analysis evaluated glycemia risk index (GRI) comparing HCL with control groups at 26 weeks post-randomization. Results: Nine participants (median [interquartile range (IQR)] age 51 [41, 59] years; 44% male; enrolment HYPO score 1183 [1058, 1308]; Clarke score 6 [6, 6]; n = 5 [HCL]; n = 4 [control]) completed the study. Time-in-range was higher using HCL vs control (70% [68, 74%] vs 48% [44, 50%], P =.014). Time <70 mg/dL did not differ (HCL 3.8% [2.7, 3.9] vs control 6.5% [4.3, 8.6], P =.14) although hypoglycemia episode duration was shorter (30 vs 50 minutes, P <.001) with HCL. Glycemia risk index was lower with HCL vs control (38.1 [30.0, 39.2] vs 70.8 [58.5, 72.4], P =.014). Following 6 months of HCL use, greater dopamine (24.0 [12.3, 27.6] vs −18.5 [−36.5, −4.8], P =.014), and growth hormone (6.3 [4.6, 16.8] vs 0.5 [−0.8, 3.0], P =.050) responses to hypoglycemia were observed. Conclusions: Six months of HCL use in high-risk adults with severe IAH increased glucose TIR and improved GRI without increased hypoglycemia, and partially restored counter-regulatory responses.

Original languageEnglish
Number of pages13
JournalJournal of Diabetes Science and Technology
Publication statusAccepted/In press - 2024


  • closed-loop systems
  • glucose counter-regulation
  • hypoglycemia
  • hypoglycemia awareness
  • type 1 diabetes

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