Reduced hypoglycemia and increased time in target using closed-loop insulin delivery during nightswith or without antecedent afternoon exercise in type 1 diabetes

Abstract

OBJECTIVE Afternoon exercise increases the risk of nocturnal hypoglycemia (NH) in subjects with type 1 diabetes. We hypothesized that automated feedback-controlled closed-loop (CL) insulin delivery would be superior to open-loop (OL) control in preventing NH and maintaining a higher proportion of blood glucose levels within the target blood glucose range on nights with and without antecedent afternoon exercise. RESEARCH DESIGN ANDMETHODSdSubjects completed two 48-h inpatient study periods in random order: usual OL control and CL control using a proportional-integrativederivative plus insulin feedback algorithm. Each admission included a sedentary day and an exercise day, with a standardized protocol of 60 min of brisk treadmill walking to 65-70% maximum heart rate at 3:00 P.M. RESULTSdAmong 12 subjects (age 12-26 years, A1C 7.4 6 0.6%), antecedent exercise increased the frequency of NH (reference blood glucose,60 mg/dL) during OL control fromsix to eight events. In contrast, there was only one NH event each on nights with and without antecedent exercise during CL control (P = 0.04 vs. OL nights). Overnight, the percentage of glucose values in target range was increased with CL control (P , 0.0001). Insulin delivery was lower between 10:00 P.M. and 2:00 A.M. on nights after exercise on CL versus OL, P = 0.008. CONCLUSIONSdCL insulin delivery provides an effective means to reduce the risk of NH while increasing the percentage of time spent in target range, regardless of activity level in the mid-afternoon. These data suggest that CL control could be of benefit to patients with type 1 diabetes even if it is limited to the overnight period. © 2013 by the American Diabetes Association.