News & Research

Manual closed-loop insulin delivery in children and adolescents with type 1 diabetes: a phase 2 randomised crossover trial, by Roman Hovorka and colleagues. The Lancet 375:743–751, 2010

What is the problem and what is known about it so far?

Type 1 diabetes is one of the most common chronic diseases of childhood and has become increasingly more common in the past 10 years. Children and adolescents with type 1 diabetes need lifelong insulin therapy to control their high blood glucose levels enough to prevent serious complications such as eye, nerve, and kidney disease. However, insulin therapy makes dangerous low blood glucose (hypoglycemia) more likely as well. The fear of hypoglycemia prevents some diabetic children and their caregivers from achieving adequate blood glucose control. Technology advances are yielding new devices to improve blood glucose monitoring and insulin therapy. Such devices can lower the risk of hypoglycemia, allowing children with diabetes to live longer, healthier lives. Continuous glucose monitoring (CGM) devices that provide around-the-clock feedback about blood glucose levels are now available. Insulin pumps allow insulin to be given slowly throughout the day at pre-set rates based on a patient’s needs. Researchers are now working to combine these two devices to form a closed-loop system in which people with diabetes receive insulin through a pump continuously throughout the day and night based on the frequent glucose measurements provided by CGM. Such a system works much the same as the pancreas in people who do not have diabetes and therefore has sometimes been called an artificial pancreas. So far, few closed-loop systems have been developed, and progress has been slow because of inaccuracies in CGM readings, problems with the way some types of insulin are absorbed in the body, and difficulties in perfecting the way the system would adjust insulin based on CGM readings to deliver the right amount of insulin at any given time. Research continues toward making a practical artificial pancreas to improve the lives of people with diabetes who require insulin.

Why did the researchers do this particular study?

The researchers wanted to find out whether a closed-loop system using a CGM device and an insulin pump could control overnight blood glucose levels safely for children and adolescents.

Who was studied?

The study included 19 patients who were 5-19 years of age and had type 1 diabetes for an average of 6 years.

How was the study done?

The researchers developed a formula for nurses to use to adjust insulin based on CGM readings. Then they performed several tests. First, patients received either standard insulin pump therapy using their pump’s pre-set rates for delivering insulin or therapy using the closed-loop system, in which nurses adjusted insulin based on CGM readings. In the second test, patients used the closed-loop system overnight after eating meals that either contained rapidly absorbed or slowly absorbed nutrients. In the third test, patients used either their standard insulin pump therapy or the closed-loop system after doing exercise in the early evening. Researchers looked at the data to see how well the closed-loop system was able to control patients’ glucose levels overnight.

What did the researchers find?

Overall, patients who used the closed-loop system spent more time in their target blood glucose range and had less hypoglycemia than those who used standard insulin pump therapy. This was particularly true after midnight, when the closed-loop system became fully effective. The closed-loop system controlled overnight glucose equally well after both types of meals and also performed well on nights after patients had exercise.

What were the limitations of the study?

The closed-loop system used in this study relied on glucose readings from CGM sensors, which are not always accurate. However, the sensors generally gave results as accurate as blood glucose test results. Improvements in CGM sensor technology could improve the performance of closed-loop systems in the future.

What are the implications of the study

Overnight insulin delivery using this closed-loop system can improve glucose control and reduce the risk of hypoglycemia in young patients with type 1 diabetes. Even before closed-loop systems are perfected and become more widely available for use around the clock, the overnight use of such systems may help reduce overnight hypoglycemia in children. Nighttime hypoglycemia is common and often goes undetected with standard therapy, especially when after-dinner high blood glucose is over-treated with insulin or early evening exercise lowers a patient’s insulin needs in the early morning hours. Improving nighttime glucose control can help children achieve better control of their diabetes and reduce the risks of hypoglycemia and complications.

FOR MORE INFORMATION

Insulin Routines

Insulin Pumps

ADA’s Guide to Raising a Child With Diabetes