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Variability of Insulin Requirements Over 12 Weeks of Closed-Loop Insulin Delivery in Adults With Type 1 Diabetes.

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Ruan, Yue 
Thabit, Hood 
Leelarathna, Lalantha 
Hartnell, Sara 
Willinska, Malgorzata E 


OBJECTIVE: To quantify variability of insulin requirements during closed-loop insulin delivery. RESEARCH DESIGN AND METHODS: We retrospectively analyzed overnight, daytime, and total daily insulin amounts delivered during a multicenter closed-loop trial involving 32 adults with type 1 diabetes. Participants applied hybrid day-and-night closed-loop insulin delivery under free-living home conditions over 12 weeks. The coefficient of variation was adopted to measure variability of insulin requirements in individual subjects. RESULTS: Data were analyzed from 1,918 nights, 1,883 daytime periods and 1,564 total days characterized by closed-loop use over 85% of time. Variability of overnight insulin requirements (mean [SD] coefficient of variation 31% [4]) was nearly twice as high as variability of total daily requirements (17% [3], P < 0.001) and was also higher than variability of daytime insulin requirements (22% [4], P < 0.001). CONCLUSIONS: Overnight insulin requirements were significantly more variable than daytime and total daily amounts. This may explain why some people with type 1 diabetes report frustrating variability in morning glycemia.



Adult, Blood Glucose, Cross-Over Studies, Diabetes Mellitus, Type 1, Female, Humans, Hypoglycemic Agents, Insulin, Insulin Infusion Systems, Male, Middle Aged, Retrospective Studies, Young Adult

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Diabetes Care

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American Diabetes Association
Wellcome Trust (100574/Z/12/Z)
European Commission (247138)
Seventh Framework Programme of the European Union (ICT FP7- 247138). Additional support for the Artificial Pancreas work by JDRF, National Institute for Health Research Cambridge Biomedical Research Centre and Wellcome Strategic Award (100574/Z/12/Z). Abbott Diabetes Care supplied discounted continuous glucose monitoring devices, sensors, and communication protocol to facilitate real-time connectivity. We acknowledge support by the staff at the Addenbrooke’s Wellcome Trust Clinical Research Facility. Jasdip Mangat and John Lum (Jaeb Center) supported development and validation of the closed-loop system. Josephine Hayes (University of Cambridge) provided administrative support. Karen Whitehead (University of Cambridge) provided laboratory support. We acknowledge support by the staff at Profil Institut; Krisztina Schmitz-Grozs provided support as a research physician, Martina Haase supported the study as an insulin pump expert, and Maren Luebkert, Kirstin Kuschma and Elke Przetak provided administrative, coordinating and documentation support.