Intensive glucose control halves complications of longstanding type 1 diabetes
Study finds improved long-term outlook when glucose is kept near normal
ANN ARBOR (July 28, 2009) — Controlling blood glucose at near-normal levels beginning as soon as possible after diagnosis would greatly improve the long-term prognosis of type 1 diabetes, concludes a study published in the July 27, 2009, issue of the Archives of Internal Medicine. The study compared overall rates of eye, kidney, and cardiovascular complications in participants from three previous research studies.
The landmark Diabetes Control and Complications Trial (DCCT), conducted from 1983 to 1989, found that intensive glucose control was superior to conventional control in delaying or preventing the complications of type 1 diabetes. Its follow-up study, the Epidemiology of Diabetes Interventions and Complications (EDIC), continues to follow DCCT participants to determine the long-term effects of prior intensive versus conventional blood glucose control. Both are funded by the National Institutes of Health.
The DCCT/EDIC study also found that the outlook for people with longstanding type 1 diabetes has greatly improved in the past 20 years due to a better understanding of the importance of intensive glucose control, as well as advances in insulin formulations, insulin delivery, glucose monitoring, and the treatment of cardiovascular risk factors.
The University of Michigan is one of three sites that have been gathering data for the DCCT/EDIC study. Division of Metabolism, Endocrinology & Diabetes faculty member William H. Herman, M.D., M.P.H. (Stefan S. Fajans/GlaxoSmithKline Professor of Diabetes, professor in the departments of Internal Medicine and Epidemiology, and director of the Michigan Diabetes Research and Training Center) is the principal investigator for the U-M site, along with Rodica Pop-Busui, M.D., Ph.D. (assistant professor, Department of Internal Medicine/Division of Metabolism, Endocrinology & Diabetes and co-director of the Michigan Neuropathy Center).
Co-Investigators at U-M include Eva Feldman, M.D., Ph.D. (Russell N. DeJong Professor of Neurology; director, Juvenile Diabetes Research Foundation for the Study of Complications in Diabetes; director, Amyotrophic Lateral Sclerosis Clinic; and director, A. Alfred Taubman Medical Research Institute), James Albers, M.D., Ph.D. (professor, Department of Neurology) and Aruna Sarma, Ph.D. (research assistant professor, Department of Urology).
Three groups of people were studied, allof whom were diagnosed with type 1 diabetes an average of 30 years earlier. Two groups consisted of DCCT/EDIC participants — those randomly assigned to intensive glucose control or to conventional control. The third group was a subset of patients in the Pittsburgh Epidemiology of Diabetes Complications (EDC) study who had conventional glucose control and who were matched to DCCT/EDIC participants by age, duration of diabetes, and degree of eye damage. The EDC, also funded by NIH, is a population-based study that has been following residents of Allegheny County, Pa., who were diagnosed with type 1 diabetes from 1950 to 1980.
After 30 years of diabetes, DCCT participants randomly assigned to intensive glucose control had about half the rate of eye damage compared to 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 cardiovascular disease events (9 percent vs. 14 percent) compared to those receiving conventional glucose control. Eye damage ranged from significant damage without vision loss to blindness. Damage to the kidneys was classified as mild kidney disease to kidney failure. Cardiovascular events encompassed heart attack, stroke, angina, and obstruction of the coronary arteries.
The intensively treated DCCT group also had lower complication rates than EDC participants, whose rates were similar to DCCT’s conventional control group: eye damage (47 percent), kidney damage (17 percent), and cardiovascular disease events (14 percent). Not only did intensive glucose control 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.
The DCCT compared intensive management of blood glucose to conventional control in 1,441 people 13 to 39 years of age with type 1 diabetes. At the time, conventional treatment consisted of one or two insulin injections a day with daily urine or blood glucose testing. Participants randomly assigned to intensive treatment were asked to keep glucose levels as close to normal as possible. That meant trying to keep hemoglobin A1C readings at 6 percent or less with at least three insulin injections a day or an insulin pump, guided by frequent self-monitoring of blood glucose. (The A1C measurement reflects average blood glucose levels over the previous two to three months.)
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 (40-53 percent) and kidney disease (35 percent) reported in the medical literature for comparable patients diagnosed in the 1950s to 1970s.
Major improvements in glucose monitoring and insulin delivery introduced in the past decade are now helping patients control their blood glucose more precisely and conveniently and reduce the risk of hypoglycemia. For example, several continuous glucose monitoring devices approved by the Food and Drug Administration give both trend and real-time information on glucose levels. Insulin pump technology is also improving, and researchers have begun testing a system that combines both technologies in patients with newly diagnosed type 1 diabetes.
Dr. Pop-Busui also published findings from the EDIC study that focused specifically on the impact of prior intensive insulin therapy on the incidence of cardiac autonomic neuropathy (CAN). Those results can be found in the June 9, 2009, edition of the American Heart Association journal Circulation.
For more information:
"Modern-Day Clinical Course of Type 1 Diabetes Mellitus After 30 Years' Duration: The Diabetes Control and Complications Trial/Epidemiology of Diabetes Interventions and Complications and Pittsburgh Epidemiology of Diabetes Complications Experience (1983–2005)"
Archives of Internal Medicine
Vol. 169, No. 14, July 27, 2009, 1307–1316