Automatic insulin pump interruption reduced nocturnal hypoglycemia

Patients who used a pump that suspended insulin delivery when it sensed a low glucose threshold were less likely to experience hypoglycemia at night than those who used a pump without a threshold sensor, an industry-funded study found.

Researchers randomly assigned patients with type 1 diabetes and documented nocturnal hypoglycemia to receive sensor-enhanced insulin pump therapy with a threshold-suspend feature (n=121) or without a threshold-suspend feature (n=126) for three months. The threshold-suspend pump pauses insulin delivery for up to two hours, without confirmation needed by the user. In the study, the intervention group's pump was set to suspend insulin delivery at sensor glucose values of 70 mg/dL or less, after which the setting could range from 70 mg/dL to 90 mg/dL.

The study's main safety outcome was change in hemoglobin A1c (HbA1c) level, and the main efficacy outcome was area under the curve (AUC) for nocturnal hypoglycemic events. Such an event was defined as a sensor glucose value of 65 mg/dL or less between 10 p.m. and 8 a.m. for more than 20 consecutive minutes and with no pump interaction within 20 minutes. Results were published June 22 in the New England Journal of Medicine.

Changes in HbA1c were negligible and similar between groups. The mean AUC for nighttime hypoglycemic events was 37.5% lower in the threshold-suspend group than the control group (P<0.001); such events occurred 31.8% less frequently in the threshold-suspend group (P<0.001). Compared to the control group, the intervention group also had significantly lower percentages of nighttime sensor glucose values at less than 50 mg/dL (57.1% less than control), 50 to less than 60 mg/dL (41.9% less), and 60 to less than 70 mg/dL (26.8% less; P<0.001 for all three ranges). There were four severe hypoglycemic events in the control group and none in the intervention group.

Results were limited in that only hypoglycemia-prone patients were enrolled, the study lasted just three months, and low glucose values that lasted less than 20 minutes weren't analyzed. While the current study didn't show differences between groups in quality of life—possibly because the study was too short—it does show that the threshold-suspend feature can lower hypoglycemia episodes, particularly at night, “without any apparent loss in overall glucose control,” the researchers concluded.

The study was funded by Medtronic MiniMed, which manufactures the pump with the suspend feature used in the study. The product is currently under review by the FDA.