Abstract
Objectives: We evaluated patterns of meal intake, insulin bolus delivery, and fingerstick glucose measurements during hybrid closed-loop and sensor-augmented pump (SAP) therapy, including associations with glucose control.Methods: Data were retrospectively analyzed from pump-treated adults with type 1 diabetes who underwent, in random order, 12 weeks free-living closed-loop (n = 32) and 12 weeks SAP (n = 33) periods. We quantified daily patterns of main meals, snacks, prandial insulin boluses, correction boluses, and fingerstick glucose measurements by analyzing data recorded on the study glucometer and on study insulin pump.Results: We analyzed 1942 closed-loop days and 2530 SAP days. The total number of insulin boluses was reduced during closed-loop versus SAP periods by mean 1.0 per day (95% confidence interval 0.6–1.4, P < 0.001) mainly because of a reduced number of correction boluses by mean 0.7 per day (0.4–1.0, P < 0.001). Other behavioral patterns were unchanged. The carbohydrate content of snacks but not the number of snacks was positively correlated with (1) glycemic variability as measured by standard deviation of sensor glucose (closed-loop P < 0.05; SAP P < 0.01), (2) mean sensor glucose (P < 0.05), and (3) postintervention HbA1c (P < 0.05). Behavioral patterns explained 47% of between-subject variance in glucose variability during SAP period and 30%–33% of variance of means sensor glucose and postintervention HbA1c.Conclusion: Fewer correction boluses are delivered during closed-loop period. The size of snacks appears to worsen glucose control possibly because of carbohydrate-rich content of snacks. Modifiable behavioral patterns may be important determinants of glucose control.
Highlights
Over the past decades, advances in continuous glucose monitoring[1] and insulin pump technologies[2] have led to improved care and quality of life in people with type 1 diabetes
The total number of insulin boluses was reduced during closed-loop versus sensor-augmented pump (SAP) periods by mean 1.0 per day (95% confidence interval 0.6–1.4, P < 0.001) mainly because of a reduced number of correction boluses by mean 0.7 per day (0.4–1.0, P < 0.001)
The total number of insulin boluses was reduced during closed-loop than during sensor-augmented pump therapy by mean 1.0 bolus per day [95% confidence interval 0.6–1.4; P < 0.001] mainly because of less frequent administration of correction boluses reduced by mean 0.7 bolus per day so that around 0.6 correction boluses were administered per day during closed loop
Summary
Advances in continuous glucose monitoring[1] and insulin pump technologies[2] have led to improved care and quality of life in people with type 1 diabetes. The accuracy and reliability of the devices have gradually increased,[1] many users do not achieve glucose targets.[3]. Two main configurations of the closed-loop control system, the single-hormone (insulin-only) and the dual-hormone systems (i.e., addition of glucagon), have been shown to offer tighter glucose control than current treatment modalities.[6] Given the delayed absorption of current subcutaneously delivered rapidacting insulin analogues, ‘‘hybrid closed-loop systems’’ benefiting from user-initiated prandial insulin boluses appear more appropriate than the fully closed-loop approach.[7] Within the hybrid closed-loop approach, user interactions may affect outcomes directly such as when omitting prandial boluses or indirectly through changes in eating habits
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