Diabetes Dateline
Fall 2009

Research News

Intensive Glucose Control Halves Complications of Longstanding Type 1 Diabetes
Study Finds Improved Long-term Outlook

Near-normal control of glucose beginning as soon as possible after diagnosis greatly improves the long-term prognosis for people with type 1 diabetes, concludes a study published July 27 in the Archives of Internal Medicine. The study also found the outlook for people with longstanding type 1 diabetes has greatly improved during the past 30 years due to a better understanding of the importance of intensive glucose control and advances in insulin formulations, insulin delivery, glucose monitoring, and cardiovascular disease (CVD) treatment.

“The remarkable improvement in long-term outcomes achieved with intensive glucose control should encourage clinicians and patients alike to implement intensive therapy as early in the course of type 1 diabetes as possible,” said lead author David M. Nathan, M.D., director of the Diabetes Center at Massachusetts General Hospital. Nathan is also co-chair of the National Institutes of Health (NIH)-funded Diabetes Control and Complications Trial (DCCT) and its follow-up study, the Epidemiology of Diabetes Interventions and Complications (EDIC).

Type 1 diabetes develops when the body’s immune system destroys pancreatic beta cells, the only cells in the body that make the hormone insulin that regulates blood glucose, also called blood sugar. In the United States, nearly 24 million people have diabetes. In adults, type 1 diabetes accounts for 5 to 10 percent of all diagnosed cases of diabetes.

The DCCT/EDIC

The DCCT, which took place between 1983 and 1993, studied 1,441 people with type 1 diabetes between the ages of 13 and 39. Participants were randomly assigned to either an intensive glucose control group or a conventional treatment group.

The intensive glucose control participants were encouraged to keep glucose levels as close to normal as possible, maintaining hemoglobin A1c (A1C) readings during the DCCT at 7 percent with at least three insulin injections a day or an insulin pump, guided by frequent self-monitoring of blood glucose. A1C readings reflect average blood glucose levels from the previous 2 to 3 months.

Conventional treatment consisted of one or two insulin injections a day with daily urine or blood glucose testing. On average, the conventional treatment group maintained A1C levels at about 9 percent.

Based on the remarkable decrease in long-term complications with intensive therapy in the DCCT, at the conclusion of the trial, investigators urged participants in the conventional treatment group to adopt intensive glucose control to manage their diabetes. More than 90 percent of DCCT participants agreed to participate in the observational EDIC follow-up.

Intensive versus Conventional Treatment

In the current analysis, the authors compared overall rates of eye, kidney, and cardiovascular complications among three groups of people diagnosed with type 1 diabetes an average of 30 years earlier. Two groups consisted of DCCT/EDIC participants: one group consisted of those who had originally been assigned to the intensive glucose control group; the other had originally been assigned to the conventional treatment group. The third group was a subset of patients in the Pittsburgh Epidemiology of Diabetes Complications (EDC) study, who were matched to DCCT/EDIC participants by age, duration of diabetes, and degree of eye damage.

The EDC, also funded by the NIH, is an observational study that has been following residents of Allegheny County, PA, who were diagnosed with type 1 diabetes between 1950 and 1980. The EDC was chosen for comparison because, as a population-based study, it provides a good snapshot of the clinical course of type 1 diabetes before the advent of intensive glucose control.

Lower Complication Rates

After 30 years of having diabetes, DCCT participants randomly assigned to intensive glucose control had less than half the rate of eye damage compared with those assigned to conventional glucose control (21 percent vs. 50 percent). They also had lower rates of kidney damage (9 percent vs. 25 percent) and CVD events (9 percent vs. 14 percent) compared with those receiving conventional glucose control. The intensively treated DCCT group also had lower complication rates than EDC participants, whose rates were similar to the DCCT’s conventional treatment group.

Not only did intensive glucose control more than halve the rates of eye and kidney damage, but the rates of vision loss and kidney failure were much lower than had been seen historically. “After 30 years of diabetes, fewer than 1 percent of those receiving intensive glucose control in the DCCT had significantly impaired vision, kidney failure, or needed a limb amputation due to diabetes,” noted Saul Genuth, M.D., a professor of medicine at Case Western University and co-chair of the EDIC. “Tight control is difficult to achieve and maintain, but its benefits have changed the course of diabetes.”

“Better treatment of blood pressure and cholesterol is also helping to reduce complication rates,” said Trevor Orchard, M.D., a professor of epidemiology at the University of Pittsburgh and head of the EDC study. “The similar event rates in the DCCT conventional control group and the EDC study suggest that the results of the DCCT trial are likely to be generally applicable to those with type 1 diabetes.”

In addition, the rates of eye damage (30 percent) and kidney disease (12 percent) in all DCCT/ EDIC participants who had type 1 diabetes for 25 years were also significantly lower than the rates of eye damage (40 to 53 percent) and kidney disease (35 percent) reported in the medical literature for comparable patients diagnosed in the 1950s to 1970s.

“These data give clinicians a realistic description of the clinical outcomes they can discuss with their patients. When intensive therapy, now the standard of care, is implemented early in the course of diabetes, most patients with type 1 diabetes should be able to avoid the disastrous long-term complications that were so common in the past,” said Nathan.

The National Institute of Diabetes and Digestive and Kidney Diseases, part of the NIH, has easy-to-read booklets and fact sheets about diabetes, including a fact sheet about the DCCT and the EDIC. For more information or to obtain copies, visit www.diabetes.niddk.nih.gov.

NIH Publication No. 10–4562
November 2009

[Top] [Next article]