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Behavioral Patterns and Associations with Glucose Control During 12-Week Randomized Free-Living Clinical Trial of Day and Night Hybrid Closed-Loop Insulin Delivery in Adults with Type 1 Diabetes

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Emami, A 
Willinska, ME 
Thabit, H 
Leelarathna, L 
Hartnell, S 


Objectives: We evaluated patterns of meal intake, insulin bolus delivery, and fingerstick glucose measurements during hybrid closed-loop and sensor-augmented pump (SAP) therapy, including associations with glucose control.

Methods: Data were retrospectively analyzed from pump-treated adults with type 1 diabetes who underwent, in random order, 12 weeks free-living closed-loop (n = 32) and 12 weeks SAP (n = 33) periods. We quantified daily patterns of main meals, snacks, prandial insulin boluses, correction boluses, and fingerstick glucose measurements by analyzing data recorded on the study glucometer and on study insulin pump.

Results: We analyzed 1942 closed-loop days and 2530 SAP days. The total number of insulin boluses was reduced during closed-loop versus SAP periods by mean 1.0 per day (95% confidence interval 0.6–1.4, P < 0.001) mainly because of a reduced number of correction boluses by mean 0.7 per day (0.4–1.0, P < 0.001). Other behavioral patterns were unchanged. The carbohydrate content of snacks but not the number of snacks was positively correlated with (1) glycemic variability as measured by standard deviation of sensor glucose (closed-loop P < 0.05; SAP P < 0.01), (2) mean sensor glucose (P < 0.05), and (3) postintervention HbA1c (P < 0.05). Behavioral patterns explained 47% of between-subject variance in glucose variability during SAP period and 30%–33% of variance of means sensor glucose and postintervention HbA1c.

Conclusion: Fewer correction boluses are delivered during closed-loop period. The size of snacks appears to worsen glucose control possibly because of carbohydrate-rich content of snacks. Modifiable behavioral patterns may be important determinants of glucose control.



behavior, closed-loop systems, insulin boluses, meals, type 1 diabetes

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Diabetes Technology and Therapeutics

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Mary Ann Liebert
National Institute of Diabetes and Digestive and Kidney Diseases (UC4DK108520)
Wellcome Trust (100574/Z/12/Z)
National Institute of Diabetes and Digestive and Kidney Diseases (DP3DK112176)
European Commission (247138)
We acknowledge support by the staff at the Addenbrooke's Wellcome Trust Clinical Research Facility. 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. Barbara Semlitsch and Markus Schauer (both from Medical University of Graz) supported the study as insulin pump experts. Funding was by Seventh Framework Programme of the European Union (ICT FP7-247138). Additional support for the Artificial Pancreas work was by JDRF, National Institute for Health Research Cambridge Biomedical Research Centre, Wellcome Strategic Award (100574/Z/12/Z), EC Horizon 2020 (H2020-SC1-731560), NIDDK (DP3DK112176 and 1UC4DK108520-01), Efficacy and Mechanism Evaluation Programme of National Institute for Health Research (14/23/09), and Helmsley Trust (Nos. 2016PG-T1D045 and 2016PG-T1D046). Abbott Diabetes Care supplied discounted continuous glucose monitoring devices, sensors, and communication protocol to facilitate real-time connectivity.