Randomized Trial of Closed-Loop Control in Very Young Children with Type 1 Diabetes.

BACKGROUND: The possible advantage of hybrid closed-loop therapy (i.e., artificial pancreas) over sensor-augmented pump therapy in very young children with type 1 diabetes is unclear. METHODS: In this multicenter, randomized, crossover trial, we recruited children 1 to 7 years of age with type 1 diabetes who were receiving insulin-pump therapy at seven centers across Austria, Germany, Luxembourg, and the United Kingdom. Participants received treatment in two 16-week periods, in random order, in which the closed-loop system was compared with sensor-augmented pump therapy (control). The primary end point was the between-treatment difference in the percentage of time that the sensor glucose measurement was in the target range (70 to 180 mg per deciliter) during each 16-week period. The analysis was conducted according to the intention-to-treat principle. Key secondary end points included the percentage of time spent in a hyperglycemic state (glucose level, >180 mg per deciliter), the glycated hemoglobin level, the mean sensor glucose level, and the percentage of time spent in a hypoglycemic state (glucose level, <70 mg per deciliter). Safety was assessed. RESULTS: A total of 74 participants underwent randomization. The mean (±SD) age of the participants was 5.6±1.6 years, and the baseline glycated hemoglobin level was 7.3±0.7%. The percentage of time with the glucose level in the target range was 8.7 percentage points (95% confidence interval [CI], 7.4 to 9.9) higher during the closed-loop period than during the control period (P<0.001). The mean adjusted difference (closed-loop minus control) in the percentage of time spent in a hyperglycemic state was -8.5 percentage points (95% CI, -9.9 to -7.1), the difference in the glycated hemoglobin level was -0.4 percentage points (95% CI, -0.5 to -0.3), and the difference in the mean sensor glucose level was -12.3 mg per deciliter (95% CI, -14.8 to -9.8) (P<0.001 for all comparisons). The time spent in a hypoglycemic state was similar with the two treatments (P = 0.74). The median time spent in the closed-loop mode was 95% (interquartile range, 92 to 97) over the 16-week closed-loop period. One serious adverse event of severe hypoglycemia occurred during the closed-loop period. One serious adverse event that was deemed to be unrelated to treatment occurred. CONCLUSIONS: A hybrid closed-loop system significantly improved glycemic control in very young children with type 1 diabetes, without increasing the time spent in hypoglycemia. (Funded by the European Commission and others; ClinicalTrials.gov number, NCT03784027.).

New therapies towards a better glycemic control in youths with type 1 diabetes.

Type 1 diabetes (T1D) is the most frequent form of diabetes in pediatric age, affecting more than 1.5 million people younger than age 20 years worldwide. Early and intensive control of diabetes provides continued protection against both microvascular and macrovascular complications, enhances growth, and ensures normal pubertal development. In the absence of definitive reversal therapy for this disease, achieving and maintaining the recommended glycemic targets is crucial. In the last 30 years, enormous progress has been made using technology to better treat T1D. In spite of this progress, the majority of children, adolescents and young adults do not reach the recommended targets for glycemic control and assume a considerable burden each day. The development of promising new therapeutic advances, such as more physiologic insulin analogues, pioneering diabetes technology including continuous glucose monitoring and closed loop systems as well as new adjuvant drugs, anticipate a new paradigm in T1D management over the next few years. This review presents insights into current management of T1D in youths.

The automated pancreas: A review of technologies and clinical practice.

Insulin pumps and glucose sensors are effective in improving diabetes therapy and reducing acute complications. The combination of both devices using an algorithm-driven interoperable controller makes automated insulin delivery (AID) systems possible. Many AID systems have been tested in clinical trials and have proven safety and effectiveness. However, currently, none of these systems are available for routine use in children younger than 6 years in Europe. For continued use, both users and prescribers must have sound knowledge of the features of the individual AID systems. Presently, all systems require various user interactions (e.g. meal announcements) because fully automated systems are not yet developed. Open-source systems are non-regulated variants to circumvent existing regulatory conditions. There are risks here for both users and prescribers. To evaluate AID therapy, the metric data of the glucose sensors, 'time in target range' and 'glucose management index', are novel recognized and suitable parameters allowing a consultation based on real glucose and insulin pump download data from the daily life of people with diabetes. Read out via cloud-based software or automatic download of such individual treatment data provides the ideal technical basis for shared decision-making through telemedicine, which must be further evaluated for general use.

Lived experience of CamAPS FX closed loop system in youth with type 1 diabetes and their parents.

AIM: To examine changes in the lived experience of type 1 diabetes after use of hybrid closed loop (CL), including the CamAPS FX CL system. MATERIALS AND METHODS: The primary study was conducted as an open-label, single-period, randomized, parallel design contrasting CL versus insulin pump (with or without continuous glucose monitoring). Participants were asked to complete patient-reported outcomes before starting CL and 3 and 6 months later. Surveys assessed diabetes distress, hypoglycaemia concerns and quality of life. Qualitative focus group data were collected at the completion of the study. RESULTS: In this sample of 98 youth (age range 6-18, mean age 12.7 ± 2.8 years) and their parents, CL use was not associated with psychosocial benefits overall. However, the subgroup (n = 12) using the CamAPS FX system showed modest improvements in quality of life and parent distress, reinforced by both survey (p < .05) and focus group responses. There were no negative effects of CL use reported by study participants. CONCLUSIONS: Closed loop use via the CamAPS FX system was associated with modest improvements in aspects of the lived experience of managing type 1 diabetes in youth and their families. Further refinements of the system may optimize the user experience.

Three-variate trajectories of metabolic control, body mass index, and insulin dose: Heterogeneous response to initiation of pump therapy in youth with type 1 diabetes.

OBJECTIVE: Continuous subcutaneous insulin infusion (CSII) in youths with type 1 diabetes (T1D) is often associated with lower HbA1c, lower total daily insulin dose (TDD), and lower body mass index (BMI) compared with multiple daily injections (MDI). Individual responses to CSII are diverse. The aim was to identify unique three-variate patterns of HbA1c, BMI standard deviation score (SDS), and TDD after switching to CSII. METHODS: Five thousand one hundred and thirty-three youths (≤20 years; 48% boys; median age at pump start 12.5 years) with T1D duration ≥3 years at CSII initiation were selected from the multicenter DPV registry. We applied group-based multitrajectory modeling to identify groups of individuals following similar trajectories. Measurements were aggregated quarterly during a 3-year follow-up period. Trajectory variables were changes of HbA1c, BMI-SDS, and TDD from baseline (delta = quarterly aggregated values at each time point [i] minus the respective baseline value). RESULTS: Four groups of diverging Delta-HbA1c, Delta-BMI-SDS, and Delta-TDD patterns were identified. All showed improvements in HbA1c during the first 3 months. Group 1 (12%) was characterized by modest HbA1c increase thereafter, TDD reduction, and stable BMI-SDS. In Group 2 (39%), increasing HbA1c, decreasing BMI-SDS, and stable TDD were found. By contrast, sustainably improved HbA1c, increasing BMI-SDS, and stable TDD were observed in Group 3 (32%). Group 4 (17%) was characterized by increasing levels for HbA1c, BMI-SDS, and TDD. Between-group differences in baseline HbA1c, BMI-SDS, TDD as well as in sex ratio, age at diabetes onset and at pump start were observed. CONCLUSIONS: Definite trajectories of glycemic control, BMI, and TDD over 3 years after CSII initiation were identified in youths with T1D allowing a more personalized treatment recommendation.

Glucose management for exercise using continuous glucose monitoring (CGM) and intermittently scanned CGM (isCGM) systems in type 1 diabetes: position statement of the European Association for the Study of Diabetes (EASD) and of the International Society for Pediatric and Adolescent Diabetes (ISPAD) endorsed by JDRF and supported by the American Diabetes Association (ADA).

Physical exercise is an important component in the management of type 1 diabetes across the lifespan. Yet, acute exercise increases the risk of dysglycaemia, and the direction of glycaemic excursions depends, to some extent, on the intensity and duration of the type of exercise. Understandably, fear of hypoglycaemia is one of the strongest barriers to incorporating exercise into daily life. Risk of hypoglycaemia during and after exercise can be lowered when insulin-dose adjustments are made and/or additional carbohydrates are consumed. Glycaemic management during exercise has been made easier with continuous glucose monitoring (CGM) and intermittently scanned continuous glucose monitoring (isCGM) systems; however, because of the complexity of CGM and isCGM systems, both individuals with type 1 diabetes and their healthcare professionals may struggle with the interpretation of given information to maximise the technological potential for effective use around exercise (i.e. before, during and after). This position statement highlights the recent advancements in CGM and isCGM technology, with a focus on the evidence base for their efficacy to sense glucose around exercise and adaptations in the use of these emerging tools, and updates the guidance for exercise in adults, children and adolescents with type 1 diabetes. Graphical abstract.

Glucose management for exercise using continuous glucose monitoring (CGM) and intermittently scanned CGM (isCGM) systems in type 1 diabetes: position statement of the European Association for the Study of Diabetes (EASD) and of the International Society for Pediatric and Adolescent Diabetes (ISPAD) endorsed by JDRF and supported by the American Diabetes Association (ADA).

Physical exercise is an important component in the management of type 1 diabetes across the lifespan. Yet, acute exercise increases the risk of dysglycaemia, and the direction of glycaemic excursions depends, to some extent, on the intensity and duration of the type of exercise. Understandably, fear of hypoglycaemia is one of the strongest barriers to incorporating exercise into daily life. Risk of hypoglycaemia during and after exercise can be lowered when insulin-dose adjustments are made and/or additional carbohydrates are consumed. Glycaemic management during exercise has been made easier with continuous glucose monitoring (CGM) and intermittently scanned continuous glucose monitoring (isCGM) systems; however, because of the complexity of CGM and isCGM systems, both individuals with type 1 diabetes and their healthcare professionals may struggle with the interpretation of given information to maximise the technological potential for effective use around exercise (ie, before, during and after). This position statement highlights the recent advancements in CGM and isCGM technology, with a focus on the evidence base for their efficacy to sense glucose around exercise and adaptations in the use of these emerging tools, and updates the guidance for exercise in adults, children and adolescents with type 1 diabetes.

Closed-loop insulin delivery in suboptimally controlled type 1 diabetes: a multicentre, 12-week randomised trial.

BACKGROUND: The 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. METHODS: In 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. FINDINGS: From 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) and bodyweight did not differ (mean difference in change 0·68 kg, 95% CI -0·34 to 1·69; p=0·19). No severe hypoglycaemia occurred. One diabetic ketoacidosis occurred in the closed-loop group due to infusion set failure. Two participants in each study group had significant hyperglycaemia, and there were 13 other adverse events in the closed-loop group and three in the control group. INTERPRETATION: Hybrid closed-loop insulin delivery improves glucose control while reducing the risk of hypoglycaemia across a wide age range in patients with suboptimally controlled type 1 diabetes. FUNDING: JDRF, NIHR, and Wellcome Trust.

Mixed-meal tolerance test to assess residual beta-cell secretion: Beyond the area-under-curve of plasma C-peptide concentration.

AIMS: Residual beta-cell secretion in type 1 diabetes is commonly assessed by area-under-curve of plasma C-peptide concentration (AUCCpep ) following mixed-meal tolerance test (MMTT). We aimed to investigate alternative measures of beta-cell responsiveness. METHODS: We analyzed data from 32 youth (age 7 to 17 years) undergoing MMTT within 6 months of type 1 diabetes diagnosis. We related AUCCpep with (a) validated mechanistic index of postprandial beta-cell responsiveness MI accounting for glucose level during MMTT, and (b) pragmatic marker calculated as baseline plasma C-peptide concentration corrected for baseline plasma glucose concentration. RESULTS: Postprandial responsiveness MI was correlated with age and BMI SDS (Rs = 0.66 and 0.44, P < 0.01 and P < 0.05) and was more correlated with glycated hemoglobin than AUCCpep (Rs = 0.79, P = 0.04). The pragmatic marker was highly correlated with AUCCpep (Rs = 0.94, P < 0.01). CONCLUSIONS: Postprandial responsiveness MI may be more relevant to glucose control than AUCCpep . Baseline C-peptide corrected for baseline glucose appears to be a suitable surrogate of AUCCpep if MMTT is not performed.

Reduced burden of diabetes and improved quality of life: Experiences from unrestricted day-and-night hybrid closed-loop use in very young children with type 1 diabetes.

OBJECTIVE: To evaluate the experiences of families with very young children aged 1 to 7 years (inclusive) with type 1 diabetes using day-and-night hybrid closed-loop insulin delivery. METHODS: Parents/caregivers of 20 children aged 1 to 7 years with type 1 diabetes completed a closed-loop experience survey following two 3-week periods of unrestricted day-and-night hybrid closed-loop insulin therapy using Cambridge FlorenceM system at home. Benefits, limitations, and improvements of closed-loop technology were explored. RESULTS: Responders reported reduced burden of diabetes management, less time spent managing diabetes, and improved quality of sleep with closed-loop. Ninety percent of the responders felt less worried about their child's glucose control using closed-loop. Size of study devices, battery performance and connectivity issues were identified as areas for improvement. Parents/caregivers wished for more options to input information to the system such as temporary glucose targets. CONCLUSIONS: Parents/caregivers of very young children reported important quality of life benefits associated with using closed-loop, supporting adoption of this technology in this population.

Hypoglycaemia incidence and recovery during home use of hybrid closed-loop insulin delivery in adults with type 1 diabetes.

Glucose excursion was assessed prior to and post hypoglycaemia to increase understanding of hypoglycaemia incidence and recovery during hybrid closed-loop insulin delivery. We retrospectively analysed data from 60 adults with type 1 diabetes who received, in a crossover randomized design, day-and-night hybrid closed-loop insulin delivery and insulin pump therapy, the latter with or without real-time continuous glucose monitoring. Over 4-week study periods, we identified hypoglycaemic episodes, defined as sensor glucose <3.0 mmol/L, and analysed sensor glucose relative to the onset of hypoglycaemia. We identified 377 hypoglycaemic episodes during hybrid closed-loop intervention vs 662 during control intervention (P < .001), with a predominant reduction of nocturnal hypoglycaemia. The slope of sensor glucose prior to hypoglycaemia was steeper during closed-loop intervention than during control intervention (P < .01), while insulin delivery was reduced (P < .01). During both day and night, participants recovered from hypoglycaemia faster when treated by closed-loop intervention. At 120 minutes post hypoglycaemia, sensor glucose levels were higher during closed-loop intervention compared to the control period (P < .05). In conclusion, closed-loop intervention reduces the risk of hypoglycaemia, particularly overnight, with swift recovery from hypoglycaemia leading to higher 2-hour post-hypoglycaemia glucose levels.

Continuous glucose monitoring and glycemic control among youth with type 1 diabetes: International comparison from the T1D Exchange and DPV Initiative.

BACKGROUND: To assess the change in rates of pediatric real-time or intermittent scanning continuous glucose monitoring (CGM) use over the past 5 years, and how it impacts glycemic control, data from two registries were compared: the US-based type 1 diabetes Exchange Registry (T1DX) and the German/Austrian DPV (Prospective Diabetes Follow-Up Registry). METHODS: Registry participants aged <18 years with T1D duration ≥1 year encompassed 29 007 individuals in 2011 and 29 150 participants in 2016. Demographic data, CGM use and hemoglobin A1c (HbA1c) were obtained from medical records. RESULTS: CGM use increased from 2011 to 2016 in both registries across all age groups, regardless of gender, ethnic minority status or insulin delivery method. The increase in CGM use was most pronounced in the youngest patients, and usage rates remain lowest for adolescent patients in 2016. For both registries in 2016, mean HbA1c was lower among CGM users regardless of insulin delivery method compared to pump only (P < 0.001) and injection only (P < 0.001), and CGM users were more likely to achieve glycemic target of HbA1c <7.5% (56% vs 43% for DPV and 30% vs 15% for T1DX, P < 0.001). T1DX participants had a higher mean HbA1c compared with DPV despite whether they were CGM users or non-users; however, the difference was less pronounced in CGM users (P < 0.001). CONCLUSIONS: Pediatric CGM use increased in both registries and was associated with lower mean HbA1c regardless of insulin delivery modality.

Faster insulin action is associated with improved glycaemic outcomes during closed-loop insulin delivery and sensor-augmented pump therapy in adults with type 1 diabetes.

We aimed to evaluate the relationship between insulin pharmacodynamics and glycaemic outcomes during closed-loop insulin delivery and sensor-augmented pump therapy. We retrospectively analysed data from a multicentre randomized control trial involving 32 adults with type 1 diabetes receiving day-and-night closed-loop insulin delivery and sensor-augmented pump therapy over 12 weeks. We estimated time-to-peak insulin action (t max,IA ) and insulin sensitivity ( S I ) during both interventions, and correlated these with demographic factors and glycaemic outcomes. During both interventions, t max,IA was positively correlated with pre- and post-intervention HbA1c (r = 0.50-0.52, P < .01) and mean glucose (r = 0.45-0.62, P < .05), and inversely correlated with time sensor glucose, which was in target range 3.9 to 10 mmol/L (r = -0.64 to -0.47, P < .05). Increased body mass index was associated with higher t max,I and lower S I (both P < .05). During closed-loop insulin delivery, t max,IA was positively correlated with glucose variability ( P < .05). Faster insulin action is associated with improved glycaemic control during closed-loop insulin delivery and sensor-augmented pump therapy.

Effects of high doses of vitamin D3 on mucosa-associated gut microbiome vary between regions of the human gastrointestinal tract.

PURPOSE: Vitamin D is well known for its effects on bone mineralisation but has also been attributed immunomodulatory properties. It positively influences human health, but in vivo data describing vitamin D effects on the human gut microbiome are missing. We aimed to investigate the effects of oral vitamin D3 supplementation on the human mucosa-associated and stool microbiome as well as CD8(+) T cells in healthy volunteers. METHODS: This was an interventional, open-label, pilot study. Sixteen healthy volunteers (7 females, 9 males) were endoscopically examined to access a total of 7 sites. We sampled stomach, small bowel, colon, and stools before and after 8 weeks of vitamin D3 supplementation. Bacterial composition was assessed by pyrosequencing the 16S rRNA gene (V1-2), and CD8(+) T cell counts were determined by flow cytometry. RESULTS: Vitamin D3 supplementation changed the gut microbiome in the upper GI tract (gastric corpus, antrum, and duodenum). We found a decreased relative abundance of Gammaproteobacteria including Pseudomonas spp. and Escherichia/Shigella spp. and increased bacterial richness. No major changes occurred in the terminal ileum, appendiceal orifice, ascending colon, and sigmoid colon or in stools, but the CD8(+) T cell fraction was significantly increased in the terminal ileum. CONCLUSION: Vitamin D3 modulates the gut microbiome of the upper GI tract which might explain its positive influence on gastrointestinal diseases, such as inflammatory bowel disease or bacterial infections. The local effects of vitamin D demonstrate pronounced regional differences in the response of the GI microbiome to external factors, which should be considered in future studies investigating the human microbiome.

Pharmacokinetics of diluted (U20) insulin aspart compared with standard (U100) in children aged 3-6 years with type 1 diabetes during closed-loop insulin delivery: a randomised clinical trial.

AIMS/HYPOTHESIS: The aim of this study was to compare the pharmacokinetics of two different concentrations of insulin aspart (B28Asp human insulin) in children aged 3-6 years with type 1 diabetes. METHODS: Young children with type 1 diabetes underwent an open-label, randomised, two-period crossover study in a clinical research facility, 2-6 weeks apart. In random order, diluted (1:5 dilution with saline [154 mmol/l NaCl]; 20 U/ml) or standard strength (100 U/ml) insulin aspart was administered via an insulin pump as a meal bolus and then overnight by closed-loop insulin delivery as determined by a model predictive algorithm. Plasma insulin was measured every 30-60 min from 17:00 hours on day 1 to 8:00 hours on day 2. We measured the time-to-peak insulin concentration (tmax), insulin metabolic clearance rate (MCR(I)) and background insulin concentration (ins(c)) using compartmental modelling. RESULTS: Eleven children (six male; age range 3.75-6.96 years, HbA1c 7.6% ± 1.3% [60 ± 14 mmol/mol], BMI standard deviation score 1.0 ± 0.8, duration of diabetes 2.2 ± 1.0 years, total daily dose 12.9 [10.6-16.5] U, fasting C-peptide concentration 5 [5-17.1] pmol/l; mean ± SD or median [interquartile range]) participated in the study. No differences between standard and diluted insulin were observed in terms of t max (59.2 ± 14.4 vs 61.6 ± 8.7) min for standard vs diluted, p = 0.59; MCR I (1.98 × 10(-2) ± 0.99 × 10(-2) vs 1.89 × 10(-2) ± 0.82 × 10(-2) 1/kg/min, p = 0.47), and ins c (34 [1-72] vs 23 [3-65] pmol/l, p = 0.66). However, t max showed less intersubject variability following administration of diluted aspart (SD 14.4 vs 8.7 min, p = 0.047). CONCLUSIONS/INTERPRETATION: Diluting insulin aspart does not change its pharmacokinetics. However, it may result in less variable absorption and could be used in young children with type 1 diabetes undergoing closed-loop insulin delivery. TRIAL REGISTRATION: Clinicaltrials.gov NCT01557634. FUNDING: FUNDING was provided by the JDRF, 7th Framework Programme of the European Union, Wellcome Trust Strategic Award and the National Institute for Health Research Cambridge Biomedical Research Centre.

Eighteen-Month Hybrid Closed-Loop Use in Very Young Children With Type 1 Diabetes: A Single-Arm Multicenter Trial.

OBJECTIVE: We aimed to evaluate the longer-term safety and efficacy of hybrid closed-loop (CL) therapy in very young children with type 1 diabetes (T1D). RESEARCH DESIGN AND METHODS: Following a 16-week multinational, randomized crossover trial comparing hybrid CL with sensor-augmented pump (SAP) therapy in 74 very young children aged 1-7 years with T1D, participants were invited to an extension phase using CL for a further 18 months. Outcomes were compared with the primary-phase SAP period and primary-phase CL period. RESULTS: After the primary study phase, 60 participants were eligible to enroll in the extension. Of these, 49 consented (mean ± SD age 6.6 ± 1.5 years) to continue use of CL for 18 months. Percentage time in range (TIR) 3.9-10.0 mmol/L was 8.4 percentage points (95% CI 6.7 to 10.1; P < 0.001) higher, while HbA1c was 0.4% ([5.0 mmol/mol], 95% CI 0.3 to 0.6 [3.7 to 6.2]; P < 0.001) lower during the CL extension phase compared with primary-phase SAP period. At 18 months, mean HbA1c was 6.7 ± 0.5% and TIR was 70 ± 7%, compared with 6.7 ± 0.5% and 71 ± 6% in the primary-phase CL period. Time in hypoglycemia (<3.9 mmol/L) was similar between CL extension phase and both primary-phase SAP (P = 0.31) and CL periods (P = 0.70). There were two severe hypoglycemia events and one other serious adverse event during the extension phase. One unexpected serious adverse device effect occurred. CONCLUSIONS: Use of the Cambridge hybrid CL system led to sustained improvements in glycemic control lasting more than 18 months in very young children with T1D.