Continuous Glucose Monitoring Helps Type 1

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ROME, Sept. 8 -- Adults with type 1 diabetes achieved significantly better glycosylated hemoglobin levels with six months of continuous monitoring than with home monitoring, researchers reported here.

But there was no benefit for patients ages 15 to 24 and for those ages eight to 14, with no significant statistical difference in between-group mean HbA1c levels, reported William Tamborlane, M.D., of Yale, at the European Association for the Study of Diabetes meeting. The findings were simultaneously published in the New England Journal of Medicine.

As a result, only patients ages 25 or older in the randomized trial of 322 children and adults by the Juvenile Diabetes Research Foundation Continuous Glucose Monitoring Study Group achieved the primary endpoint, a significant change in glycated hemoglobin from baseline.
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In the 25 and older group, there was a mean reduction of 0.53% (95% CI -0.71 to -0.35, P<0.001). There was also a significant between-group difference favoring those age 25 or older in the continuous glucose monitoring arm (P=0.003)

Across all groups there was no increase in hypoglycemia, Dr. Tamborlane said.

In the youngest age group, a secondary analysis found that patients in the continuous glucose monitoring arm were more likely to have glycated hemoglobin levels of less than 7% (P=0.01) and to have achieved a relative reduction of 10% (P=0.04) or more from baseline.

Despite the secondary nature of that finding, co-investigator Irl B. Hirsch, M.D., of the University of Washington in Seattle, said it was an important observation because the landmark Diabetes Control and Complication Trial (DCCT) found that a 10% reduction in glycated hemoglobin correlated with a 40% reduction in the development and progression of diabetic retinopathy.

For example, a reduction of that magnitude could reduce the rate of diabetic nephropathy from 2.7 per 100 patients years to 1.8 per 100 patient years, Dr. Hirsch said.

Given the results, it was not surprising that patients ages 25 or older used continuous glucose monitoring more often than those in the other groups. Of those 25 or older, 83% used continuous glucose monitoring six or more days per week. Those ages 15 to 24 had the lowest use rate, with only 30% using the devices six days or more a week. The youngest patients had a six-day use rate of 50%.

From February through December 2007, the trial recruited 322 adults and children who were receiving intensive therapy for type 1 diabetes, defined as use of an insulin pump or more than three insulin injections daily, Of them 165 were randomized to continuous glucose monitoring and 157 to home monitoring with a glucose meter.

The mean baseline HbA1c level was 8% or less. Ninety-eight patients were 25 or older, 110 were 15 to 24, and 114 were eight to 14.

Follow-up visits were conducted at one, four, eight, 13, 19, and 26 weeks, and 95% to 100% of patients across all groups completed all visits.

Patients in the continuous glucose monitoring arm received one of three devices: DexCom Seven (DexCom), the MiniMed Paradigm Real-Time Insulin Pump and Continuous Glucose Monitoring System (Medtronic), or the Free Style Navigator (Abbott Diabetes Care).

Patients were told to use the device daily and to verify the accuracy of glucose measurement using a home blood glucose monitor supplied by the trial. Control patients received home monitors and were told to perform home monitoring at least four times a day.

In each arm patients were given detailed instructions on how to use the data to make adjustments in insulin doses.

Irrespective of treatment group, targeted premeal glucose values were 70 to 130 mg/dL or 3.9 to 7.2 mmol/liter, peak postpranial values (<180 mg per deciliter or 10.0 mmol/liter), and bedtime-overnight values were 100 to 150 mg/dL or 5.6 to 8.3 mmol/liter.

Dr. Hirsch cautioned that the results might not be widely generalizable because the patients in the trial were already committed to intensive insulin therapy with either insulin pumps or multiple injections.

The take-home message, he said, was that continuous glucose monitoring was effective in patients who are willing to change their behavior. Its best effect was among patients who are willing to use the technology 24/7, he said.

"It means thinking more about your diabetes, not thinking less about it," he said.