Effect of Continuous Glucose Monitoring on Glycemic Control in Adults With Type 1 Diabetes Using Insulin Injections

Importance

Previous clinical trials showing the benefit of continuous glucose monitoring (CGM) in the management of type 1 diabetes predominantly have included adults using insulin pumps, even though the majority of adults with type 1 diabetes administer insulin by injection.

Objective

To determine the effectiveness of CGM in adults with type 1 diabetes treated with insulin injections.

Design, Setting, and Participants

Randomized clinical trial conducted between October 2014 and May 2016 at 24 endocrinology practices in the United States that included 158 adults with type 1 diabetes who were using multiple daily insulin injections and had hemoglobin A_1c(HbA_1c) levels of 7.5% to 9.9%.

Interventions

Random assignment 2:1 to CGM (n = 105) or usual care (control group; n = 53).

Main Outcomes and Measures

Primary outcome measure was the difference in change in central-laboratory–measured HbA_1clevel from baseline to 24 weeks. There were 18 secondary or exploratory end points, of which 15 are reported in this article, including duration of hypoglycemia at less than 70 mg/dL, measured with CGM for 7 days at 12 and 24 weeks.

Results

Among the 158 randomized participants (mean age, 48 years [SD, 13]; 44% women; mean baseline HbA_1clevel, 8.6% [SD, 0.6%]; and median diabetes duration, 19 years [interquartile range, 10-31 years]), 155 (98%) completed the study. In the CGM group, 93% used CGM 6 d/wk or more in month 6. Mean HbA_1creduction from baseline was 1.1% at 12 weeks and 1.0% at 24 weeks in the CGM group and 0.5% and 0.4%, respectively, in the control group (repeated-measures modelP < .001). At 24 weeks, the adjusted treatment-group difference in mean change in HbA_1clevel from baseline was –0.6% (95% CI, –0.8% to –0.3%;P < .001). Median duration of hypoglycemia at less than <70 mg/dL was 43 min/d (IQR, 27-69) in the CGM group vs 80 min/d (IQR, 36-111) in the control group (P = .002). Severe hypoglycemia events occurred in 2 participants in each group.

Conclusions and Relevance

Among adults with type 1 diabetes who used multiple daily insulin injections, the use of CGM compared with usual care resulted in a greater decrease in HbA_1clevel during 24 weeks. Further research is needed to assess longer-term effectiveness, as well as clinical outcomes and adverse effects.

Trial Registration

clinicaltrials.gov Identifier:NCT02282397