Updated May 22, 2006

Diabetes Control and Complications Trial

A landmark study that proved that tight blood glucose control can substantially reduce the risk of developing the devastating medical complications of diabetes. At least as early as the 1930's, researchers hotly debated what role blood glucose levels played in diabetic complications, without any solid scientific evidence to back up their claims. In the ensuing decades, a lot changed.

In the early 1980's, for example, the hemoglobin A1c (HbA_1c) test came into widespread use and was shown to be a reliable and useful indicator of long-term blood glucose control. Meanwhile, the development of an affordable portable blood glucose meter enabled more and more people with diabetes to monitor their blood glucose levels on their own and more frequently. Increasing numbers of people also began using insulin pumps and newly designed multiple-injection regimens. Researchers developed ways to objectively measure and quantify varying degrees of diabetic complications. At the same time, there was an increased interest in promoting evidence-based medicine, a system in which treatment decisions are based on a combination of the results of scientific studies and a physician's clinical judgment rather than on a mixture of tradition, personal experience, and educated guessing.

All of these developments set the stage for the Diabetes Control and Complications Trial (DCCT). This scientifically rigorous study compared the effects of intensive insulin with conventional insulin regimens in 1,441 people with Type 1 diabetes over an average period of 6 1/2 years. The intensively treated group received four daily insulin injections or continuous insulin infusion from an insulin pump, guided by frequent blood glucose monitoring. The conventional treatment group received only one or two daily insulin injections, with less frequent blood glucose monitoring.

The results? Overall, blood glucose levels stayed closer to the normal range in the intensively treated group: The HbA_1c level was 7.2% in that group, while it was 8.9% in the conventionally treated group. In addition, the effect of intensive treatment on diabetic complications was stunning. Intensive insulin therapy reduced the risk of developing diabetic retinal disease by 76%, diabetic nerve disease by 60%, and diabetic kidney disease by 54%. These results were published in a 1993 issue of The New England Journal of Medicine.

Subsequent studies called the Kumamoto Study and the United Kingdom Prospective Diabetes Study showed that tight control with insulin or oral drugs has similar benefits in people with Type 2 diabetes.

In 2005, the results of a follow-up study to the DCCT showed that tight control lowered the risk of heart disease. Earlier results from that trial, published in 2003, had shown that tight control lowered the risk of atherosclerosis, a precursor to heart disease.

Thanks to these studies, tight control has become the new standard of treatment for people with diabetes. Researchers are now focusing on how to make this intensive therapy more user-friendly, more accessible, and less burdensome to people with diabetes.

This article was written by Robert S. Dinsmoor, a Contributing Editor of Diabetes Self-Management.

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