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Aims We explored whether, how and why moving onto and using a hybrid day‐and‐night closed‐loop system affected people's food choices and dietary practices to better understand the impact of this technology on everyday life and inform recommendations for training and support given to future users. Methods Twenty‐four adults, adolescents and parents were interviewed before commencing use of the closed‐loop system and following its 3‐month use. Data were analysed thematically and longitudinally. Results While participants described preparing and/or eating similar meals to those consumed prior to using a closed‐loop, many described feeling more normal and less burdened by diabetes in dietary situations. Individuals also noted how the use of this technology could lead to deskilling (less precise carbohydrate counting) and less healthy eating (increased snacking and portion sizes and consumption of fatty, energy‐dense foods) because of the perceived ability of the system to deal with errors in carbohydrate counting and address small rises in blood glucose without a corrective dose needing to be administered. Conclusions While there may be quality‐of‐life benefits to using a closed‐loop, individuals might benefit from additional nutritional and behavioural education to help promote healthy eating. Refresher training in carbohydrate counting may also be necessary to help ensure that users are able to undertake diabetes management in situations where the technology might fail or that they take a break from using it., What's new? This is the first study to explore how moving onto and using a closed‐loop system may affect people's food choices and eating practices.Using a closed‐loop can help people to feel more normal, and less anxious and burdened by diabetes in dietary situations.While we did not find the level of unrestrained eating behaviour hypothesized by others, we did observe some potential slippage into increased snacking and unhealthier eating as a result of using a closed‐loop.We support recommendations for people to be given tailored training and nutritional support to help promote healthy eating while using a closed‐loop.

Aim: To compare bolus insulin delivery patterns during closed-loop home studies in adults with suboptimally [HbA1c 58-86 mmol/mol (7.5%-10%)] and well-controlled [58 mmol/mol (< 7.5%)] Type 1 diabetes. Methods: Retrospective analysis of daytime and night-time insulin delivery during home use of closed-loop over 4 weeks. Daytime and night-time controller effort, defined as amount of insulin delivered by closed-loop relative to usual basal insulin delivery, and daytime bolus effort, defined as total bolus insulin delivery relative to total daytime insulin delivery were compared between both cohorts. Correlation analysis was performed between individual bolus behaviour (bolus effort and frequency) and daytime controller efforts, and proportion of time spent within and below sensor glucose target range. Results: Individuals with suboptimally controlled Type 1 diabetes had significantly lower bolus effort (P = 0.038) and daily bolus frequency (P < 0.001) compared with those with well-controlled diabetes. Controller effort during both daytime (P = 0.007) and night-time (P = 0.005) were significantly higher for those with suboptimally controlled Type 1 diabetes. Time when glucose was within the target range (3.9-10.0 mmol/L) during daytime correlated positively with bolus effort (r = 0.37, P = 0.016) and bolus frequency (r = 0.33, P = 0.037). Time when glucose was below the target range during daytime was comparable in both groups (P = 0.36), and did not correlate significantly with bolus effort (r = 0.28, P = 0.066) or bolus frequency (r = -0.21, P = 0.19). Conclusion: More frequent bolusing and higher proportion of insulin delivered as bolus during hybrid closed-loop use correlated positively with time glucose was in target range. This emphasises the need for user input and educational support to benefit from this novel therapeutic modality.

Aim To compare bolus insulin delivery patterns during closed‐loop home studies in adults with suboptimally [HbA1c 58–86 mmol/mol (7.5%–10%)] and well‐controlled [58 mmol/mol (< 7.5%)] Type 1 diabetes. Methods Retrospective analysis of daytime and night‐time insulin delivery during home use of closed‐loop over 4 weeks. Daytime and night‐time controller effort, defined as amount of insulin delivered by closed‐loop relative to usual basal insulin delivery, and daytime bolus effort, defined as total bolus insulin delivery relative to total daytime insulin delivery were compared between both cohorts. Correlation analysis was performed between individual bolus behaviour (bolus effort and frequency) and daytime controller efforts, and proportion of time spent within and below sensor glucose target range. Results Individuals with suboptimally controlled Type 1 diabetes had significantly lower bolus effort (P = 0.038) and daily bolus frequency (P < 0.001) compared with those with well‐controlled diabetes. Controller effort during both daytime (P = 0.007) and night‐time (P = 0.005) were significantly higher for those with suboptimally controlled Type 1 diabetes. Time when glucose was within the target range (3.9–10.0 mmol/L) during daytime correlated positively with bolus effort (r = 0.37, P = 0.016) and bolus frequency (r = 0.33, P = 0.037). Time when glucose was below the target range during daytime was comparable in both groups (P = 0.36), and did not correlate significantly with bolus effort (r = 0.28, P = 0.066) or bolus frequency (r = –0.21, P = 0.19). Conclusion More frequent bolusing and higher proportion of insulin delivered as bolus during hybrid closed‐loop use correlated positively with time glucose was in target range. This emphasises the need for user input and educational support to benefit from this novel therapeutic modality., What's new? Glucose control during hybrid closed‐loop therapy is linked to bolusing behaviour.Closed‐loop users with well‐controlled Type 1 diabetes bolused more frequently without increasing the risk of hypoglycaemia.We highlight the importance of user input and education to gain optimal benefit from hybrid closed‐loop.

AIMS: We explored whether, how and why moving onto and using a hybrid day-and-night closed-loop system affected people's food choices and dietary practices to better understand the impact of this technology on everyday life and inform recommendations for training and support given to future users. METHODS: Twenty-four adults, adolescents and parents were interviewed before commencing use of the closed-loop system and following its 3-month use. Data were analysed thematically and longitudinally. RESULTS: While participants described preparing and/or eating similar meals to those consumed prior to using a closed-loop, many described feeling more normal and less burdened by diabetes in dietary situations. Individuals also noted how the use of this technology could lead to deskilling (less precise carbohydrate counting) and less healthy eating (increased snacking and portion sizes and consumption of fatty, energy-dense foods) because of the perceived ability of the system to deal with errors in carbohydrate counting and address small rises in blood glucose without a corrective dose needing to be administered. CONCLUSIONS: While there may be quality-of-life benefits to using a closed-loop, individuals might benefit from additional nutritional and behavioural education to help promote healthy eating. Refresher training in carbohydrate counting may also be necessary to help ensure that users are able to undertake diabetes management in situations where the technology might fail or that they take a break from using it.

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 ($_Ix}$) 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.

AIMS: To evaluate safety, efficacy and glucose turnover during closed-loop with meal announcement using reduced prandial insulin boluses in adolescents with type 1 diabetes (T1D). METHODS: We conducted a randomized crossover study comparing closed-loop therapy with standard prandial insulin boluses versus closed-loop therapy with prandial boluses reduced by 25%. Eight adolescents with T1D [3 males; mean (standard deviation) age 15.9 (1.5) years, glycated haemoglobin 74 (17) mmol/mol; median (interquartile range) total daily dose 0.9 (0.7, 1.1) IU/kg/day] were studied on two 36-h-long visits. In random order, subjects received closed-loop therapy with either standard or reduced insulin boluses administered with main meals (50-80 g carbohydrates) but not with snacks (15-30 g carbohydrates). Stable-label tracer dilution methodology measured total glucose appearance (Ra_total) and glucose disposal (Rd). RESULTS: The median (interquartile range) time spent in target (3.9-10 mmol/l) was similar between the two interventions [74 (66, 84)% vs 80 (65, 96)%; p = 0.87] as was time spent above 10 mmol/l [21.8 (16.3, 33.5)% vs 18.0 (4.1, 34.2)%; p = 0.87] and below 3.9 mmol/l [0 (0, 1.5)% vs 0 (0, 1.8)%; p = 0.88]. Mean plasma glucose was identical during the two interventions [8.4 (0.9) mmol/l; p = 0.98]. Hypoglycaemia occurred once 1.5 h post-meal during closed-loop therapy with standard bolus. Overall insulin delivery was lower with reduced prandial boluses [61.9 (55.2, 75.0) vs 72.5 (63.6, 80.3) IU; p = 0.01] and resulted in lower mean plasma insulin concentration [186 (171, 260) vs 252 (198, 336) pmol/l; p = 0.002]. Lower plasma insulin was also documented overnight [160 (136, 192) vs 191 (133, 252) pmol/l; p = 0.01, pooled nights]. Ra_total was similar [26.3 (21.9, 28.0) vs 25.4 (21.0, 29.2) µmol/kg/min; p = 0.19] during the two interventions as was Rd [25.8 (21.0, 26.9) vs 25.2 (21.2, 28.8) µmol/kg/min; p = 0.46]. CONCLUSIONS: A 25% reduction in prandial boluses during closed-loop therapy maintains similar glucose control in adolescents with T1D whilst lowering overall plasma insulin levels. It remains unclear whether closed-loop therapy with a 25% reduction in prandial boluses would prevent postprandial hypoglycaemia.