Abstract
The closed-loop system (artificial pancreas) delivers insulin in a glucose-responsive manner by the use of a control algorithm that automatically directs insulin delivery, based on real-time sensor glucose concentrations. Results from hospital-based studies have shown improved overnight glucose control and reduced risk of hypoglycaemia in type 1 diabetes. We aimed to assess whether unsupervised closed-loop systems can provide a realistic treatment option in patients with type 1 diabetes.
We combined data from two open-label, phase 2, randomised, cross-over, unsupervised home trials of people with type 1 diabetes, one in 24 adults (mean age 43 years [SD 12], HbA1c 8·0% [0·9]) and the other in 16 adolescents (15·6 [3·6], 8·1 [0·8]). In each trial, after training on study devices, participants were allocated to two periods of sensor-augmented pump therapy either with or without overnight closed loop that used a model predictive control algorithm to direct insulin delivery. Allocation sequence was done with a computer-generated random code. Each period lasted 4 weeks in adults and 3 weeks in adolescents. Primary outcome for both trials was time when sensor glucose was in the target range (3·9–8·0 mmol/L). Analysis was by intention to treat. Participants (or parents) gave written informed consent. The trials are registered with ClinicalTrials.gov, numbers NCT01440140 and NCT01221467.
Closed loop was started by participants on their own volition on 866 (89%) of 978 nights. The proportion of time when sensor glucose was in the target range between 0000 h and 0800 h was increased by a mean of 18·4% (95% CI 13·5–23·4, p<0·0001) during closed loop compared with no closed loop. Closed loop significantly reduced mean overnight sensor glucose by 0·9 mmol/L (95% CI 0·4–1·3, p=0·0001), and reduced the proportion of time when sensor glucose values were suggestive of hyperglycaemia (>8·0 mmol/L) (15·9%, 10·7–21·0; p<0·0001) and hypoglycaemia (<3·9 mmol/L) (median 0·9, IQR 0·2–2·2; p=0·014). Lower mean overnight glucose was associated with increased overnight insulin delivery (p<0·0001) without changing total daily insulin amount (p=0·84).
Extended use of overnight closed loop at home without supervision is feasible in adults and adolescents with type 1 diabetes. Clinically significant reduction in overnight glucose was observed accompanied by reduced time spent by patients in hypoglycaemia. To our knowledge, such combined effect has not been documented with any other means of intensified conventional insulin delivery. Longer term studies are warranted to assess its clinical potential.
Diabetes UK, Juvenile Diabetes Research Foundation, NIHR Cambridge Biomedical Research Centre.