Spotlight Article

Application of continuous glucose monitoring to identify nocturnal hypoglycemia in people with type 1 diabetes

Eric Renard

Diabetic Hypoglycemia June 2012, Volume 5, Issue 1: page 12-14

Abstract

Hypoglycemia is the main adverse event related to insulin therapy, and intensive insulin therapy to maintain near-normoglycemia increases its occurrence. Nocturnal events are particularly feared by people with type 1 diabetes since the risk of it being undetected is higher, and can result in severe outcomes related to neuroglycopenia. The availability of continuous glucose monitoring (CGM) during the last decade has changed the epidemiology of nocturnal hypoglycemia in people with type 1 diabetes. Unexpected, frequent and prolonged periods of nocturnal hypoglycemia have been revealed in children, adolescents and adults treated with various insulin regimens. In most cases, the individual was completely unaware of the hypoglycemia. The limited accuracy of the glucose sensors that measure interstitial subcutaneous glucose, which is then converted to estimated blood glucose levels through calibration of the sensor signal against capillary glucose, has raised some doubts about the reliability of CGM recordings. Nevertheless, adaptation of insulin doses or regimens based upon CGM observations has shown some effectiveness in reducing nocturnal hypoglycemia. However, almost daily use of CGM has not been associated with a significant reduction in the frequency of nocturnal hypoglycemia. This may be because most patients are not awakened from sleep by alarms triggered by low glucose concentrations. A more effective way of preventing severe or prolonged nocturnal hypoglycemia comes from connecting the sensor signal to algorithms that stop or reduce insulin delivery when low blood glucose is either detected or predicted.

Keywords: type 1 diabetes, nocturnal hypoglycemia, continuous glucose monitoring