According to the results of this multicentre study, the use of continuous glucose monitoring reduced the time that patients on intensive therapy for type 1 diabetes spent in hypoglycaemia, with a concomitant decrease in HbA1c.

The authors note that intensive insulin treatment increases exposure to hypoglycaemia; this may be associated with permanent damage to the CNS.  Devices that continuously monitor glucose have been introduced to aid self-management and these have been shown to improve HbA1c levels.  Although clinical practice recommendations suggest that continuous monitoring may be especially useful in patients with hypoglycaemia unawareness and/or frequent episodes of hypoglycaemia, the hypoglycaemia preventative effect of continuous monitoring has not yet been demonstrated.  The purpose of their study was therefore to assess the impact of continuous glucose monitoring on hypoglycaemia in people with type 1 diabetes.

The study included 120 children and adults (ages 10-65 years) with type 1 diabetes and an HbA1c of <7.5% at screening, who were using intensive insulin treatment with either a pump or multiple daily injections.  Following a four-week run-in period (in which their usual monitoring was used, with recording of hypoglycaemia events, food intake and insulin doses), participants were randomised to a control group (home monitoring with a blood glucose meter and wearing a masked continuous glucose monitor for 5 days every other week) or to real-time continuous glucose monitoring, wearing individual sensors for 5 days continuously for 26 weeks (continuous monitoring group).  Patients and investigators were masked for the continuous glucose monitoring data in the control group.

The continuous glucose monitoring system used in the study was the FreeStyle Navigator (Abbott Diabetes Care), which measures glucose in interstitial fluid.  The primary outcome was the time spent in hypoglycaemia (interstitial glucose concentration <63mg/dL) over a period of 26 weeks (intention-to-treat analysis).    This was found to be shorter in the continuous monitoring group – a mean of 0.48 hours per day versus 0.97 hours per day in the control group (ratio of means 0.49; 95% CI 0.26–0.76; P=0.03).  The HbA1c was lower at 26 weeks in the continuous monitoring group (difference of −0.27%; 95% CI −0.47 to −0.07; P=0.008) and the time spent in normoglycaemia (70 to 180 mg/dL) was longer (mean of 17.6 vs. 16.0 hours per day, respectively; P=0.009).

The authors note that their results should be interpreted with caution, as the patients and their families were highly motivated, demonstrating good metabolic control and an average of over five glucose readings per day prior to randomisation.  In addition it was not possible to blind patients and investigators to the intervention and so the results are “less compelling”.  They say that further studies are required to evaluate the effect of continuous glucose monitoring on prevention of hypoglycaemia in les well controlled and less motivated patient populations with type 1 diabetes.