medwireNews: Use of the Tandem Control IQ hybrid closed-loop insulin delivery system improves time in range (TIR) even for users who very rarely bolus for meals or to treat hyperglycemia, an observational study suggests.
“We still advocate using meal-time boluses and user-initiated correction boluses if necessary, in Tandem Control IQ users for optimal glycemic control,” say Halis Kaan Akturk (University of Colorado, Aurora, USA) and co-researchers.
“However, we think these data show compelling evidence that hybrid closed-loop pumps using Tandem Control IQ can achieve large improvements in glycemic control even among people who are not bolusing.”
The study included 30 adults with type 1 diabetes using the system, 10 of whom had more than 90% of their daily insulin bolus delivered automatically in response to predicted high blood glucose levels.
“These patients were almost completely dependent for auto boluses since they did not give any boluses for meals or correction,” the study authors write in Diabetes Technology & Therapeutics.
Nevertheless, after 12 months of using the system, during which their bolusing habits did not change, these people’s TIR improved by approximately 15% from an average baseline of 38.9%, with three of the 10 achieving TIR above 70%. And their average glycated hemoglobin (HbA1c) level improved by nearly 1.5% from a baseline of 9.7% (83 mmol/mol).
The largest TIR gains were seen in the 10 people, matched for age, sex, diabetes duration, and duration of insulin pump use, who had 50–90% of their insulin bolus needs met via automatic corrections by the system. These people had an average TIR increase of about 30% from a baseline of 39.7%, and their HbA1c improved by nearly 2% from an average of 9.4% (79 mmol/mol).
The researchers also looked at an additional group of 10 matched Tandem Control IQ users who had only 10–49% of their bolus needs met automatically by the system. These people had the highest baseline average TIR, of 46.1%, and improved by about 22% over 12 months, while their HbA1c improved by about 1.3% from a baseline average of 9.0% (75 mmol/mol).
Of note, the group with intermediate reliance on automatic boluses had significantly better TIR than both people with high reliance and those with low reliance.
This finding “shows that overbolusing as much as underbolusing is a barrier to achieve optimal glycemic control and that emphasizes the importance of [the] auto bolus feature in this system,” note the study authors.
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Diabetes Technol Ther 2022; doi:10.1089/dia.2022.0162