Can a sensor-augmented insulin pump decrease the incidence of hypoglycemia?

The authors compared the incidence rates of moderate and severe hypoglycemia in traditional insulin pump therapy and sensor-augmented pump therapy.

Hypoglycemia (dangerously low blood glucose levels) is a critical obstacle to care of patients with type 1 diabetes. Type 1 diabetes patients require insulin therapy to replace the insulin that is normally produced by the body. One method of insulin delivery is an insulin pump; a small computerized device that delivers both a steady and measured dose of insulin and a surge of insulin at mealtimes.

Sensor-augmented pump therapy with an automated low glucose suspension function is an improvement on the traditional pump therapy. It combines the technology of an insulin pump with a continuous glucose sensor that transmits glucose readings to the person wearing the device. This allows insulin delivery to be ceased automatically for up to 2 hours when sensor glucose falls below a preset threshold.

Early reports suggest this method is safe and reduces the amount of time that patients spend in the hypoglycemic range (below 70 mg/dL). The authors of this study aimed to determine the incidence of severe and moderate hypoglycemia with a sensor-augmented pump with low-glucose suspension compared with standard insulin pump therapy.

95 patients with type 1 diabetes were randomly assigned to either pump-only therapy (49 patients) or sensor-augmented pump with low-glucose suspension function. Patients were deemed to have low hypoglycemia awareness (diminished or absent ability to perceive hypoglycemia symptoms) and the average age was 18 years. The average duration of diabetes was 11 years, while the average duration of previous pump therapy was 4.1 years. Treatment was undertaken for 6 months.

After 6 months of treatment, the absolute number of moderate and severe hypoglycemic events decreased from 175 to 35 in the low-glucose suspension group. The absolute number of events decreased from 28 to 6 in the pump-only group.

 This was associated with a decrease in the incidence rate (the number of new cases in a population at risk in a given time period) of moderate or severe hypoglycemia from 129.6 events per 100 patient-months (a measure of the rate of risk over time) to 9.5 for the low-glucose suspension group. There appeared to be an increase in the incidence rate of moderate or severe hypoglycemia from 20.7 to 34.2 for the pump-only group. The incidence of hypoglycemia was 3.6 times more likely to occur in the pump-only group than the low-glucose suspension group.

There was no change in HbA1c levels (a measurement of average blood glucose levels over the past 3 months).

By the end of the study the low-glucose suspension group spent an average of 4.1 hours per day and 4.4 hours per night in the hypoglycemic range (blood glucose levels less than 70 mg/dL). By the end of the study the pump-only group spent an average of 6.9 hours per day and 11.8 hours per night in the hypoglycemic range.

The authors found that the use of sensor-augmented pump therapy with low-glucose suspension reduced the rate of severe and moderate hypoglycemia in patients with type 1 diabetes over a 6-month period. 

The patients were younger and had shorter duration of diabetes than the more typical patient with hypoglycemia unawareness, so the conclusions may not be transferable to those patients.