Hybrid Closed Loop in High Risk Youth With Type 1 Diabetes

T1D is among the most common chronic childhood illness, affecting an estimated 1 in 400 American children.2 The care of children and adolescents with type 1 diabetes aims to optimize glycemic control to prevent acute and chronic complications of both hypoglycemia and hyperglycemia.

CGMs are minimally invasive devices that use a subcutaneous sensor to report and record changes in interstitial glucose values every 5 minutes to 15 minutes.6 This technology can alert patients to hypoglycemia and hyperglycemia and also allows them to make diabetes treatment decisions without the need for a confirmatory fingerstick blood glucose level. Improvements in the accuracy and usability of CGM, better insurance coverage, and greater acceptance by both clinicians and patients have led to dramatic increases in the use of this technology over the past decade.1,7-15 In 2011, just 6% of all patients in the United States Type 1 Diabetes Exchange (T1DX) registry were using CGM as compared to 27% in the period from 2016-2018.1 The use of CGM therapy has been associated with decreased hypoglycemia and severe hypoglycemia,16,17 improvements in A1c,1 reduced fear of hypoglycemia,18 and improved diabetes treatment satisfaction.19 Insulin pump therapy provides a continuous subcutaneous infusion of rapid acting insulin that allows for more physiologic insulin delivery as compared to multiple daily injection therapy. The use of insulin pump therapy in children with T1D has been associated with improved glycemic control, decreased rates of DKA, lower risk for microvascular complications, as well as psychosocial benefits.

Recently, input from CGM has been used to guide automated insulin delivery through insulin pumps in what is referred to as HCL insulin delivery. The Control IQ algorithm developed by Tandem Diabetes Care, Inc. uses a Dexcom G6 to adjust insulin delivery according to predicted glucose levels in 30 minutes to maximize TIR. Control IQ was FDA approved for patients with T1D ≥ 14 years of age in December 2019 and for patients ≥ 6 years of age in June 2020. A 6-month randomized controlled study of the Control IQ algorithm showed improvements in mean glucose, TIR, time in hypoglycemia, and time in hyperglycemia.25 Although Control IQ was shown to have positive impacts on glycemic control, its impact on those in poor glycemic control remains largely unknown. Prior studies included only a selected population: 86% of participants were white, 86% of participants had at least a bachelor's degree, 62% had an annual household income >$100,000, and the average A1c on enrollment was 7.4 ± 1.0%.

The increasing use of insulin pumps and continuous glucose monitors (CGM) among people with Type 1 diabetes (T1D) has been associated with worsening already existing healthcare disparities among people of different races, ethnicities, and socioeconomic statuses. Studies have shown that CGM use is more likely among participants with higher household incomes, greater levels of parental education, and those with private healthcare insurance.8 The disparities in access to these technologies persist even after controlling for these factors, which raises concern for clinician bias in prescribing these technologies despite evidence from an RCT that CGM use is equally beneficial for children of different racial and ethnic groups.26 There has been an ongoing push to better understand the various factors contributing to these disparities in access to diabetes technologies.27 Evidence that technology use varies according to geographic location speaks to the role of provider preference as well as patient socioeconomic status.28 The association between black race and higher rates of DKA and mortality in patients with T1D <25 years of age may impact provider insulin pump prescribing practices.29 While ongoing work is necessary to better understand factors impacting prescribing practices, the addition of data supporting the effectiveness of HCL therapy without higher rates of DKA in underserved patients can only help to strengthen this argument.

We aim to explore the effect of HCL insulin therapy with the Control IQ system on glycemic control as measured by time in range (TIR) in underserved youths ≥ 6 to < 21 years of age with poorly controlled T1D. For the purposes of this study, because of the lowest rates of diabetes technology use in this group, underserved patients will be defined as: non-Hispanic black with public healthcare insurance being managed with insulin regimens using either NPH or sliding scales. Poorly controlled T1D will be defined as: at least two A1c values ≥10% in the preceding year. We have specifically chosen these inclusion criteria for the purposes of this pilot study because we wish to show the effectiveness of using these technologies in patients who are the least likely to have access to diabetes technologies.