Effect of continuous glucose monitoring on hypoglycemia in type 1 diabetes

OBJECTIVE

To assess the impact of continuous glucose monitoring on hypoglycemia in people with type 1 diabetes.

RESEARCH DESIGN AND METHODS

In this randomized, controlled, multicenter study, 120 children and adults on intensive therapy for type 1 diabetes and a screening level of glycated hemoglobin A_1c (HbA_1c) <7.5% were randomly assigned to a control group performing conventional home monitoring with a blood glucose meter and wearing a masked continuous glucose monitor every second week for five days or to a group with real-time continuous glucose monitoring. The primary outcome was the time spent in hypoglycemia (interstitial glucose concentration <63 mg/dL) over a period of 26 weeks. Analysis was by intention to treat for all randomized patients.

RESULTS

The time per day spent in hypoglycemia was significantly shorter in the continuous monitoring group than in the control group (mean ± SD 0.48 ± 0.57 and 0.97 ± 1.55 h/day, respectively; ratio of means 0.49; 95% CI 0.26–0.76; P = 0.03). HbA_1c at 26 weeks was lower in the continuous monitoring group than in the control group (difference −0.27%; 95% CI −0.47 to −0.07; P = 0.008). Time spent in 70 to 180 mg/dL normoglycemia was significantly longer in the continuous glucose monitoring group compared with the control group (mean hours per day, 17.6 vs. 16.0, P = 0.009).

CONCLUSIONS

Continuous glucose monitoring was associated with reduced time spent in hypoglycemia and a concomitant decrease in HbA_1c in children and adults with type 1 diabetes.The benefits of intensive treatment of type 1 diabetes, established almost 20 years ago (1), are difficult to achieve, despite the increased use of insulin analogs and insulin pumps, with only a minority of patients maintaining their glycated hemoglobin A_1c (HbA_1c) within the target range (2). Intensive insulin treatment and lower HbA_1c increase exposure to hypoglycemia (3,4). The risk of hypoglycemia is even higher in children and adolescents (5,6) and increases with the duration of diabetes (7). Frequent hypoglycemia is associated with hypoglycemia unawareness (8,9), which may in turn lead to reduced adherence to therapeutic decisions (10). Finally, hypoglycemia may be associated with permanent damage to the central nervous system (11) and may permanently influence cognitive functions in children (12) but not in adults (13).Recently, devices for real-time continuous glucose monitoring have been introduced to aid self-management of glycemic control and have been shown to improve HbA_1c levels in people with type 1 diabetes (14–17). In clinical practice recommendations, it has also been suggested that continuous glucose monitoring is especially useful in patients with hypoglycemia unawareness and/or frequent episodes of hypoglycemia (18). However, the hypoglycemia preventive effect of continuous glucose monitoring has not been established. Therefore, we designed a randomized, controlled, multicenter clinical trial to evaluate the effect of continuous glucose monitoring on hypoglycemia in children and adults with type 1 diabetes.