Glucose monitoring devices benefit people with type 1 diabetes

May 27 2009

People with type 1 diabetes who have already been successful in achieving recommended blood sugar goals can further benefit from using continuous glucose monitoring (CGM) devices, according to results of a major multi-center clinical trial by the Juvenile Diabetes Research Foundation. Findings of the study were published online by the journal Diabetes Care.

According to the JDRF study, using CGM devices enables people who have achieved excellent control (with HbA1c levels below 7 percent) to continue to tightly manage their diabetes while cutting down on the frequency of low blood sugars, called hypoglycemia. Research has shown that good blood sugar control is a key factor in reducing the risk of the devastating long-term complications of the disease, such as blindness and kidney disease - but that the fear of low blood sugar emergencies often prevents many people from achieving tight control, and remains a constant concern for those who manage their diabetes well. The landmark Diabetes Control and Complications Trial (DCCT) showed that with intensive insulin therapy, excellent blood glucose control was obtained, but at the expense of a considerable increase in hypoglycemia. Today, the JDRF study has shown that, with CGM, hypoglycemia can be reduced while maintaining excellent blood sugar control.

The CGM study was a randomized and controlled trial involving 129 adults and children ranging in age from 8 to 69-years-old at 10 sites, including the Atlanta Diabetes Associates, the Joslin Diabetes Center, Kaiser Permanente Southern California, Nemours Children's Clinic - Jacksonville, FL, the Lucile Packard Children's Hospital at Stanford University, the Barbara Davis Center for Childhood Diabetes at the University of Colorado Denver, the University of Iowa, the University of Washington, and Yale University, and coordinated by the Jaeb Center for Health Research in Tampa, Florida. Participants all had good diabetes control when they enrolled in the trial, and were randomly assigned to either a group that used CGM devices or one using standard finger-stick glucose testing for 26 weeks.

"The research suggests that CGM devices helped people who were already doing an excellent job of managing their diabetes continue to do so, while lowering the risk of pushing their blood sugar so low it causes hypoglycemia, which can be life threatening," said Dr. Bruce Bode, Atlanta Diabetes Associates and one of the lead authors of the Diabetes Care paper. "These trials are showing that CGM not only helps people get into control, which can have a significant positive impact on lowering the risk of complications, but it enables them to stay in control without increasing the near-term risk of hypoglycemia. That's terrific news for people with diabetes and their families."

(People with diabetes try to maintain their blood sugar levels between 70 mg/dL and 180 mg/dL. When blood sugar becomes very low, people can become confused, lethargic, and even slip into a coma or die. Very high blood sugars can also be dangerous. And long term, lack of control increases the risk of developing devastating complications, including eye, kidney, nerve, and heart disease. HbA1c is a measure of long term blood sugar control; standards of good control are generally below 7% for adults, and below 7.5% to 8% for children, depending on age. According to the DCCT findings, every one point reduction in HbA1c reduces the risk of long-term complications by approximately 40%.)

According to the study, for the people using CGM devices the time the blood sugar level was below 70 mg/dL decreased by 37 minutes a day. This compared with a decrease in the control group of only 5 minutes a day. In other words, people in the CGM group spent almost two hours more time per day in the target blood sugar range of 71 to 180 mg/dL compared with the control group, and about half an hour less time per day with glucose values in the potentially dangerous hypoglycemia range. The authors demonstrated a number of other significant benefits in this population including:

• more people in the CGM group had an improvement in HbA1c of more than 0.3% (31% versus 5% in the control group)
• fewer had a worsening of HbA1c greater than 0.3% (28% versus 52%)
• more CGM users had a HbA1c level below 7% at 26 weeks (88% versus 63%)
• more people in the CGM group than the control group had a decrease in HbA1c of more than 0.3% without experiencing a severe hypoglycemic event (28% versus 5%).

Encouragingly, similar beneficial results were seen in children, adolescents, and adults spanning the ages of 8 to 69 years.

Dr. Aaron Kowalski, Program Director for Metabolic Control at JDRF, explained that in planning this study, the change in HbA1c was not selected as the primary outcome measure because the researchers did not anticipate being able to lower HbA1c levels in the CGM group, given their already exquisite level of control. He noted that the study group expected that there might even be small and clinically insignificant increases in HbA1c values in the CGM group if the devices were able to help them reduce the frequency of glucose levels below 70 mg/dL. Instead, the CGM group was able to maintain HbA1c levels with less biochemical hypoglycemia, whereas HbA1c levels rose over time in the control group. He noted that all the HbA1c outcomes favored the CGM over the control group.

Major eligibility criteria for the study included people over the age of 8 who had type 1 diabetes for at least one year, who either used an insulin pump or took at least three daily insulin injections, and had HbA1c levels below 7.0%. Subjects in the control group were given blood glucose meters and test strips and asked to perform blood glucose monitoring at least four times daily, and met with study personnel as often as the CGM group.

The study is the second major publication resulting from JDRF's groundbreaking CGM trials, established to clinically document the benefits of CGM devices in helping people with type 1 diabetes manage their disease more effectively. In results published last fall in The New England Journal of Medicine, the JDRF Continuous Glucose Monitoring Study Group reported that CGM substantially improved blood sugar levels without increasing the frequency of hypoglycemia in adults over 25 years of age in a randomized trial of 322 adults and children with type 1 diabetes and HbA1c levels above 7 percent. (Like virtually every other study of a new drug or device in the treatment of type 1 diabetes, because lowering of HbA1c was the primary outcome of interest, that study excluded individuals already reaching target HbA1c levels lower than 7 percent. As a result, the study group also conducted a separate, concurrent randomized trial to evaluate the efficacy and safety of CGM in adults and children with type 1 diabetes who already had successfully achieved HbA1c levels less than 7 percent with intensive insulin therapy.) More information on the initial results of JDRF's CGM trials and on the Artificial Pancreas Project is available online at http://www.artificialpancreas.org.

Dr. Kowalski noted that over the past 15 years, the use of rapid and long-acting insulin analogs, improvements in insulin pumps, and more frequent home blood glucose monitoring have had a positive impact on the ability of people with type 1 diabetes to achieve blood sugar control targets. However, the rates of severe hypoglycemia remain too high and the occurrence of such events is often followed by a decline in glycemic control due to fears of further hypoglycemic episodes. Hypoglycemia remains the major limiting factor for people with type 1 diabetes in trying to achieve and maintain good blood sugar control. These study results are extremely encouraging in showing that hypoglycemia can be reduced without sacrificing glycemic control.