Can a closed-loop system reduce hypoglycemia after exercise in patients with type 1 diabetes?

This study looked at how the Diabeloop system managed exercise for patients with type 1 diabetes (T1D). It found that people using this system did not have more hypoglycemia (dangerously low blood sugar) on days with exercise.

Physical exercise is a cornerstone of good health. Its many benefits include improved heart health, balance, weight management, and mental health. Many people find it difficult to maintain a regular exercise practice. However, people with type 1 diabetes (T1D) face particular challenges in exercising.

People with T1D do not naturally make the hormone insulin, which controls the amount of glucose (sugar) in the blood. To prevent harmful high blood glucose, people with T1D take synthetic insulin. However, exercise also uses glucose from the blood as energy. If the dose of insulin is not adjusted, exercise can cause hypoglycemia or low blood sugar. Hypoglycemia can have serious complications.

People with T1D adjust their insulin levels and/or eat carbohydrate snacks prior to exercise, to maintain their blood glucose levels. However, getting the right balance can be challenging, particularly with traditional insulin injections. Closed-loop systems can be simpler. These systems connect a continuous glucose monitor to an insulin pump, to automatically adjust insulin levels.

The Diabeloop Generation-1 is a closed-loop system. The Diabeloop is adjusted by the user through a smartphone app. If the user inputs their plan to exercise into the Diabeloop app, it will adjust insulin and give the user recommendations on whether to eat a snack. It is not clear whether the Diabeloop can improve blood glucose control following exercise.

This study included 63 adults with T1D who started using the Diabeloop closed-loop system. Patients exercised according to their normal routines. They were asked to input their planned exercise into the Diabeloop app at least an hour ahead of time. The app asks how long they plan to exercise, and whether it will be mild, moderate, or intense. The study lasted 12 weeks.

The Diabeloop recommended carbohydrate snacks as needed. The app recommended significantly more carbohydrates on days with exercise (41.1 vs. 21.8 g/day). At the same time, there was significantly less insulin on days with exercise (31.5 vs. 34.0 U/day).

The researchers measured how much of the day the participants’ blood glucose was above or below the target (70 to 180 mg/dL). There was a similar amount of time with low glucose on days with and without exercise (2.0% vs. 2.2%). However, there was significantly more time with high blood glucose on days with exercise (28.7% vs. 26.8%).

This study found that the Diabeloop system adjusted insulin and carbohydrates on days with exercise so the patients with T1D did not have more hypoglycemia after exercise.

This study was funded by Diabeloop. This paper was an additional write-up added onto a larger study and was not planned in advance. The paper did not compare Diabeloop to another glucose management system.