SummaryBackgroundThe achievement of glycaemic control remains challenging for patients with type 1 diabetes. We assessed the effectiveness of day-and-night hybrid closed-loop insulin delivery compared with sensor-augmented pump therapy in people with suboptimally controlled type 1 diabetes aged 6 years and older.MethodsIn this open-label, multicentre, multinational, single-period, parallel randomised controlled trial, participants were recruited from diabetes outpatient clinics at four hospitals in the UK and two centres in the USA. We randomly assigned participants with type 1 diabetes aged 6 years and older treated with insulin pump and with suboptimal glycaemic control (glycated haemoglobin [HbA1c] 7·5–10·0%) to receive either hybrid closed-loop therapy or sensor-augmented pump therapy over 12 weeks of free living. Training on study insulin pump and continuous glucose monitoring took place over a 4-week run-in period. Eligible subjects were randomly assigned using central randomisation software. Allocation to the two study groups was unblinded, and randomisation was stratified within centre by low (<8·5%) or high (≥8·5%) HbA1c. The primary endpoint was the proportion of time that glucose concentration was within the target range of 3·9–10·0 mmol/L at 12 weeks post randomisation. Analyses of primary outcome and safety measures were done in all randomised patients. The trial is registered with ClinicalTrials.gov, number NCT02523131, and is closed to accrual.FindingsFrom May 12, 2016, to Nov 17, 2017, 114 individuals were screened, and 86 eligible patients were randomly assigned to receive hybrid closed-loop therapy (n=46) or sensor-augmented pump therapy (n=40; control group). The proportion of time that glucose concentration was within the target range was significantly higher in the closed-loop group (65%, SD 8) compared with the control group (54%, SD 9; mean difference in change 10·8 percentage points, 95% CI 8·2 to 13·5; p<0·0001). In the closed-loop group, HbA1c was reduced from a screening value of 8·3% (SD 0·6) to 8·0% (SD 0·6) after the 4-week run-in, and to 7·4% (SD 0·6) after the 12-week intervention period. In the control group, the HbA1c values were 8·2% (SD 0·5) at screening, 7·8% (SD 0·6) after run-in, and 7·7% (SD 0·5) after intervention; reductions in HbA1c percentages were significantly greater in the closed-loop group compared with the control group (mean difference in change 0·36%, 95% CI 0·19 to 0·53; p<0·0001). The time spent with glucose concentrations below 3·9 mmol/L (mean difference in change −0·83 percentage points, −1·40 to −0·16; p=0·0013) and above 10·0 mmol/L (mean difference in change −10·3 percentage points, −13·2 to −7·5; p<0·0001) was shorter in the closed-loop group than the control group. The coefficient of variation of sensor-measured glucose was not different between interventions (mean difference in change −0·4%, 95% CI −1·4% to 0·7%; p=0·50). Similarly, total daily insulin dose was not different (mean difference in change 0·031 U/kg per day, 95% CI −0·005 to 0·067; p=0·09...

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<b>Objective: </b>International type 1 diabetes registries have shown that HbA1c levels are highest in young people with type 1 diabetes, however improving their glycaemic control remains a challenge. We propose that use of factory-calibrated Dexcom G6 CGM system would improve glycaemic control in this cohort. <p><b>Research Design and Methods: </b>We conducted a randomized crossover trial in young people with type 1 diabetes (16 – 24 years old), comparing the Dexcom G6 CGM system and self-monitoring of blood glucose (SMBG). Participants were assigned to the interventions in random order during two 8-week study periods. During SMBG, blinded CGM was worn by each participant for 10 days at the start, week-4 and week-7 of the control period. HbA1c measurements were drawn after enrolment, before and after each treatment period. The primary outcome was time in range 70–180mg/dl.</p> <p><b>Results: </b>Time in range was significantly higher during CGM compared to control [35.7±13.5% vs. 24.6±9.3%, mean difference 11.1% (95% CI 7.0 to 15.2, p<0.001)]. CGM use reduced mean sensor glucose [219.7±37.6mg/dl vs. 251.9±36.3mg/dl, mean difference -32.2mg/dl (95% CI -44.5 to -20.0, p<0.001)] and time above range [61.7±15.1% vs. 73.6±10.4%, mean difference 11.9% (95% CI -16.4 to -7.4, p<0.001)]. HbA1c level was reduced by 0.76% (95% CI -1.1 to -0.4) [-8.5mmol/mol (95% CI -12.4 to -4.6, p<0.001)]. Times spent below range (<70mg/dl and <54mg/dl) were low and comparable during both study periods. Sensor wear was 84% during the CGM period.</p> <p><b>Conclusion: </b>CGM use in young people with type 1 diabetes improves time in target and HbA1c levels compared to SMBG.<b> </b></p>