; for the CGM Intervention in Teens and Young Adults with T1D (CITY) Study Group IMPORTANCE Adolescents and young adults with type 1 diabetes exhibit the worst glycemic control among individuals with type 1 diabetes across the lifespan. Although continuous glucose monitoring (CGM) has been shown to improve glycemic control in adults, its benefit in adolescents and young adults has not been demonstrated. OBJECTIVE To determine the effect of CGM on glycemic control in adolescents and young adults with type 1 diabetes. DESIGN, SETTING, AND PARTICIPANTS Randomized clinical trial conducted between January 2018 and May 2019 at 14 endocrinology practices in the US including 153 individuals aged 14 to 24 years with type 1 diabetes and screening hemoglobin A 1c (HbA 1c) of 7.5% to 10.9%. INTERVENTIONS Participants were randomized 1:1 to undergo CGM (CGM group; n = 74) or usual care using a blood glucose meter for glucose monitoring (blood glucose monitoring [BGM] group; n = 79). MAIN OUTCOMES AND MEASURES The primary outcome was change in HbA 1c from baseline to 26 weeks. There were 20 secondary outcomes, including additional HbA 1c outcomes, CGM glucose metrics, and patient-reported outcomes with adjustment for multiple comparisons to control for the false discovery rate. RESULTS Among the 153 participants (mean [SD] age, 17 [3] years; 76 [50%] were female; mean [SD] diabetes duration, 9 [5] years), 142 (93%) completed the study. In the CGM group, 68% of participants used CGM at least 5 days per week in month 6. Mean HbA 1c was 8.9% at baseline and 8.5% at 26 weeks in the CGM group and 8.9% at both baseline and 26 weeks in the BGM group (adjusted between-group difference, −0.37% [95% CI, −0.66% to −0.08%]; P = .01). Of 20 prespecified secondary outcomes, there were statistically significant differences in 3 of 7 binary HbA 1c outcomes, 8 of 9 CGM metrics, and 1 of 4 patient-reported outcomes. The most commonly reported adverse events in the CGM and BGM groups were severe hypoglycemia (3 participants with an event in the CGM group and 2 in the BGM group), hyperglycemia/ketosis (1 participant with an event in CGM group and 4 in the BGM group), and diabetic ketoacidosis (3 participants with an event in the CGM group and 1 in the BGM group). CONCLUSIONS AND RELEVANCE Among adolescents and young adults with type 1 diabetes, continuous glucose monitoring compared with standard blood glucose monitoring resulted in a small but statistically significant improvement in glycemic control over 26 weeks. Further research is needed to understand the clinical importance of the findings.

OBJECTIVEIntense exercise is a major challenge to the management of type 1 diabetes (T1D). Closed-loop control (CLC) systems (artificial pancreas) improve glycemic control during limited intensity and short duration of physical activity (PA). However, CLC has not been tested during extended vigorous outdoor exercise common among adolescents.RESEARCH DESIGN AND METHODSSkiing presents unique metabolic challenges: intense prolonged PA, cold, altitude, and stress/fear/excitement. In a randomized controlled trial, 32 adolescents with T1D (ages 10–16 years) participated in a 5-day ski camp (∼5 h skiing/day) at two sites: Wintergreen, VA, and Breckenridge, CO. Participants were randomized to the University of Virginia CLC system or remotely monitored sensor-augmented pump (RM-SAP). The CLC and RM-SAP groups were coarsely paired by age and hemoglobin A1c (HbA1c). All subjects were remotely monitored 24 h per day by the study physicians and clinical team.RESULTSCompared with physician-monitored open loop, percent time in range (70–180 mg/dL) improved using CLC: 71.3 vs. 64.7% (+6.6% [95% CI 1–12]; P = 0.005), with maximum effect late at night. Hypoglycemia exposure and carbohydrate treatments were improved overall (P = 0.001 and P = 0.007) and during the daytime with strong ski level effects (P = 0.0001 and P = 0.006); ski/snowboard proficiency was balanced between groups but with a very strong site effect: naive in Virginia and experienced in Colorado. There was no adverse event associated with CLC; the participants’ feedback was overwhelmingly positive.CONCLUSIONSCLC in adolescents with T1D improved glycemic control and reduced exposure to hypoglycemia during prolonged intensive winter sport activities, despite the added challenges of cold and altitude.

Objective: To describe glycemic and psychosocial outcomes in youth with type 1 diabetes using a hybrid closed loop (HCL) system. Subjects: Youth with type 1 diabetes (2-25 years) starting the 670G HCL system for their diabetes care were enrolled in an observational study. Methods: Prospective data collection occurred during routine clinical care and included glycemic variables (sensor time in range [70-180 mg/dL], HbA1c), and psychosocial variables (Hypoglycemia Fear Survey [HFS]; Problem Areas in Diabetes [PAID]). Mixed models were used to analyze change across time.Results: Ninety-two youth (mean age 15.7 ± 3.6 years, 50% female, HbA1c 8.8% ± 1.8%) started HCL for their diabetes care. Youth used Auto Mode 65.5% ± 3.0% of the time at month 1, which decreased to 51.2% ± 3.4% at month 6 (P = .001). Sensor time in range increased from 50.7% ± 1.8% at baseline to 56.9% ± 2.1% at 6 months (P = .007). HbA1c decreased from 8.7% ± 0.2% at baseline to 8.4% ± 0.2% after 6 months of use (P ≤ .0001), with the greatest HbA1c decline in participants with high baseline HbA1c. Increased percent time in auto mode was associated with lower HbA1c (P = .02). Thirty percent of youth discontinued HCL in the first 6 months of use. There were no changes in the HFS or PAID scores across time.Conclusions: HCL use is associated with improved glycemic control and no change in psychosocial outcomes in this clinical sample. The decline in HCL use across time suggests that youth experience barriers in sustaining use of HCL. Further research is needed to understand reasons for HCL discontinuation and determine intervention strategies.pediatrics, artificial pancreas, automated insulin delivery, continuous glucose monitor The use of diabetes technology is a promising treatment strategy to improve diabetes outcomes in youth. Use of insulin pumps and continuous glucose monitors (CGM) are associated with reduction in HbA1c, both when used separately and together. 7 The most advanced technology currently available for diabetes care is a hybrid closed loop (HCL) insulin delivery system. HCL technology automates basal insulin delivery in response to CGM glucose trends while users deliver bolus doses for carbohydrate consumption. The MiniMed 670G is the first HCL device to be commercially available, which consists of the 670G insulin pump and the Guardian 3 CGM.The 670G operates in two modes, both as a standard insulin pump ("Manual Mode"), and as HCL ("Auto Mode"). 8 When using the 670G system in Auto Mode, the basal insulin delivery is calculated every 5 min by the pump's HCL algorithm, based on sensor glucose data. 9 To maintain Auto Mode use, the user must wear the CGM consistently, calibrate the CGM sensor at least twice per day, and respond to alerts in a timely manner. The system exits users from Auto Mode to Manual Mode if: (a) there is prolonged hyperglycemia (ie, sensor glucose >250 mg/dL for 3 h or >300 mg/dL for 1 h); (b) the pump has delivered a minimum or maximum insulin rate for 1-3 h; or (c) sensor glucose data are missing or inaccurate...

Objective: To describe predictors of hybrid closed loop (HCL) discontinuation and perceived barriers to use in youth with type 1 diabetes.Subjects: Youth with type 1 diabetes (eligible age 2-25 y; recruited age 8-25 y) who initiated the Minimed 670G HCL system were followed prospectively for 6 mo in an observational study.Research Design and Methods: Demographic, glycemic (time-in-range, HbA1c), and psychosocial variables [Hypoglycemia Fear Survey (HFS); Problem Areas in Diabetes (PAID)] were collected for all participants. Participants who discontinued HCL (<10% HCL use at clinical visit) completed a questionnaire on perceived barriers to HCL use.Results: Ninety-two youth (15.7 ± 3.6 y, HbA1c 8.8 ± 1.3%, 50% female) initiated HCL, and 28 (30%) discontinued HCL, with the majority (64%) discontinuing between 3 and 6 mo after HCL start. Baseline HbA1c predicted discontinuation (P = .026) with the odds of discontinuing 2.7 times higher (95% CI: 1.123, 6.283) for each 1% increase in baseline HbA1c. Youth who discontinued HCL rated difficulty with calibrations, number of alarms, and too much time needed to make the system work as the most problematic aspects of HCL. Qualitatively derived themes included technological difficulties (error alerts, not working correctly), too much work (calibrations, fingersticks), alarms, disappointment in glycemic control, and expense (cited by parents).Conclusions: Youth with higher HbA1c are at greater risk for discontinuing HCL than youth with lower HbA1c, and should be the target of new interventions to support device use. The primary reasons for discontinuing HCL relate to the workload required to use HCL. K E Y W O R D Sartificial pancreas, continuous glucose monitor, insulin pump, hybrid closed loop, pediatrics, type 1 diabetes Type 1 diabetes (T1D), typically diagnosed in childhood 1,2 requires lifelong replacement of exogenous insulin, and monitoring of glucose levels to minimize hypoglycemia and hyperglycemia. 3 Long-term consequences of suboptimal glycemic control include both microvascular and macrovascular complications that increase morbidity and mortality for individuals with T1D. 3 Sub-optimal glycemic control also increases risk of emergent complications such as hypoglycemic seizures and loss of consciousness, and diabetic ketoacidosis or diabetic coma. 4,5 The T1D Exchange Registry recently showed that in the United States only 21% of adults and 17% of youth with T1D meet hemoglobin A1c (HbA1c) goals set forth by the American Diabetes Association, signifying the need for improvements in treatment and care of T1D. 6

A bolus of rapid-acting insulin 20 min prior to a meal results in significantly better postprandial glucose control than when the meal insulin bolus is given just prior to the meal or 20 min after meal initiation.

In transitioning young patients to the 670G system, providers should anticipate immediate C-to-I ratio adjustments while also assessing active insulin time. Users should anticipate occasional Auto Mode exits, which can be reduced by following system instructions and reliably bolusing for meals. Unique 670G system functionality requires ongoing clinical guidance and education from providers.

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