Unsupervised home use of a closed-loop insulin delivery system, also known as an artificial beta cell, is feasible and safe, and more effective than a sensor-augmented insulin pump for adults and children with type 1 diabetes, according to a report published in the New England Journal of Medicine.
The closed-loop insulin delivery system differs from conventional pump therapy “in that it uses a control algorithm that autonomously and continually increases and decreases the subcutaneous delivery of insulin” based on real-time glucose levels monitored by sensors. These devices have been studied extensively under controlled laboratory conditions and in transitional outpatient settings (including diabetes camps) that included monitoring and supervision by nearby research staff. But until now, only two studies have assessed the devices in at-home, free-living conditions, and those were limited to 1 week of daytime and nighttime use among adults and 3-6 weeks of overnight use in adolescents and adults, said Dr. Hood Thabit of the Wellcome Trust–Medical Research Council Institute of Metabolic Science and the department of diabetes and endocrinology, Cambridge University Hospitals National Health Service Foundation Trust, and his associates.
They performed two multicenter open-label, randomized crossover trials assessing 12 weeks of a closed-loop insulin delivery system (intervention period) and 12 weeks of conventional insulin-pump therapy (control period) in study participants who performed their usual daily activities and were free to consume foods of their choice. In one study, 33 adults (mean age, 40 years) used the closed-loop system during day and at night while awake, both at home and at work. In the other study, 25 children and adolescents aged 6-18 years (mean age, 12 years) used the closed-loop system overnight while asleep.
The primary endpoint of both studies was the proportion of time that the glucose level remained within the target range, which was 70-180 mg/dL in the adults and 70-145 mg/dL for the children and adolescents. This was significantly greater during the intervention period than during the control period for both the adults (by a mean of 11 percentage points) and the children and adolescents (by a mean of 25 percentage points).
In addition, in both studies the mean glucose level was significantly lower, the time spent in a hypoglycemic range was significantly less, the glycated hemoglobin level was significantly lower, and glucose variability was significantly lower during the intervention period than in the control period.
“The advantage of a closed-loop system is the responsive, graduated modulation of insulin delivery, both below and above the preset pump regimen, which allows for improvements in the proportion of time spent in target glucose range and the lowering of the mean glucose level without increasing the risk of hypoglycemia,” Dr. Thabit and his associates wrote (New Engl J Med. 2015;373:2129-40).
There were two serious adverse events. One adult had an episode of severe hypoglycemia when the closed-loop system was not in use because of low battery power and the patient was receiving insulin through a conventional sensor-augmented pump. And one adolescent had two episodes of severe hypoglycemia, also when the closed-loop system was not turned on and the patient was receiving insulin through a sensor-augmented pump. Both participants recovered without clinical sequelae.
This study was supported by the European Union, the U.K. National Institute for Health Research Cambridge Biomedical Research Centre, and Wellcome Trust. Abbott Diabetes Care provided continuous glucose-monitoring devices and sensors at a discount, and Diasend provided hardware and software platforms at a discount, but neither had any role in the study. Two of the authors reported holding patents related to insulin-delivery systems. Dr. Thabit reported having no relevant financial disclosures; several of his associates reported ties to numerous industry sources.