The time needed to reliably assess closed-loop performance in adults with sub-optimal glucose control (A1c 59 to 86 mmol/mol) including changes in behavioral adaptation is currently unknown. We combined data from 2 multi-national randomized closed-loop studies of 12-week duration (N=56; mean±SD, A1c 68±7mmol/mol, age 39±10 year, diabetes duration 21±9 year). For each participant, glucose sensor metrics were computed for the full 12-week period and restricting data to 60 time periods representing 1 to 60 days. For each metric, the association between the value from each sampling period and the value using all 12 weeks of data, determined using Pearson or Spearman correlation coefficient (r). The number of days needed to reach an ‘r’ value of 0.95 (equaling 90% of total variance) for different metrics, mean glucose, % time >180 mg/dl, 70-180mg/dL, >250mg/dL, <70mg/dl, <54mg/dl and coefficient of variation were 27, 24, 26, 33, 38, 49 and 47 days, respectively. Closed-loop usage was consistent throughout sampling periods between 80 and 82%.

In conclusion, closed-loop studies of 4-week duration are likely to provide representative data for mean glucose, normoglycemia and hyperglycemia while 6 weeks may be required for a reliable estimate of hypoglycemia and glucose variability.

Figure: Correlation coefficients of data collected over the full 12-week period and taken over the first 60 days.


L. Leelarathna: Advisory Panel; Self; Abbott, Dexcom, Inc., Medtronic, Novo Nordisk A/S, Roche Diabetes Care, Sanofi-Aventis. Research Support; Self; Dexcom, Inc., Novo Nordisk Inc. Speaker’s Bureau; Self; Insulet Corporation, Medtronic, Novo Nordisk A/S, Roche Diabetes Care, Sanofi. H. Thabit: Research Support; Self; Dexcom, Inc. M.E. Wilinska: None. L. Bally: None. J.K. Mader: Advisory Panel; Self; Boehringer Ingelheim International GmbH, Eli Lilly and Company, Prediktor Medical, Roche Diabetes Care, Sanofi. Speaker’s Bureau; Self; Abbott, AstraZeneca, Dexcom, Inc., Novo Nordisk Inc. Stock/Shareholder; Self; decide Clinical Software GmbH. S. Arnolds: None. C. Benesch: None. T.R. Pieber: Advisory Panel; Self; ADOCIA, Arecor Limited, AstraZeneca, Novo Nordisk A/S, Sanofi. Speaker’s Bureau; Self; Novo Nordisk A/S. V.N. Shah: Advisory Panel; Self; Sanofi US. Consultant; Self; Dexcom, Inc. A.L. Carlson: Consultant; Self; Sanofi US. Research Support; Self; Abbott, Dexcom, Inc., JDRF, Medtronic, National Institutes of Health, Novo Nordisk A/S. R.M. Bergenstal: Research Support; Self; Abbott, Boehringer Ingelheim Pharmaceuticals, Inc., Dexcom, Inc., Glooko, Inc., Hygieia, JDRF, Johnson & Johnson Medical Devices Companies, Lilly Diabetes, Medtronic MiniMed, Inc., Merck & Co., Inc., National Institute of Diabetes and Digestive and Kidney Diseases, Novo Nordisk Inc., Roche Diabetes Care, Sanofi. Other Relationship; Self; Abbott, Helmsley Charitable Trust, Hygieia, Lilly Diabetes, Novo Nordisk Inc., Onduo LLC, Sanofi, UnitedHealth Group Inc. M. Evans: Advisory Panel; Self; Dexcom, Inc., Medtronic, Roche Diabetes Care, Zucara Therapeutics Inc. Research Support; Self; MedImmune, Sanofi. Speaker’s Bureau; Self; AstraZeneca. Other Relationship; Self; Abbott, Eli Lilly and Company, Novo Nordisk Inc. R. Hovorka: Advisory Panel; Self; Novo Nordisk A/S. Research Support; Self; Abbott, Dexcom, Inc., Medtronic. Speaker’s Bureau; Self; Eli Lilly and Company, Novo Nordisk A/S. Other Relationship; Self; B. Braun Medical Inc., Medtronic.

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