The Diabetes Control and Complications Trial (DCCT)

The Diabetes Control and Complications Trial was launched by the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) in 1981 when requests for proposals were issued for clinical centers and a central Data Coordinating Center. In early 1982 the Biostatistics Center of the George Washington University was awarded the contract to serve as the Coordinating Center with Dr. John M. Lachin as Principal Investigator and Director, and Ms. Patricia Cleary as Co-Director. In addition, 29 clinical centers in the United States and Canada, and 8 central laboratories and units participated in the trial. The Coordinating Center contract spanned the period 1982-1998. The complete study group is listed in the Appendix to the principal publication of study results in The New England Journal of Medicine.

Since the discovery of insulin in 1921, the medical community debated the glucose hypothesis that the marked elevation of blood glucose (hyperglycemia) associated with diabetes mellitus was responsible for the development and progression of the microvascular complications of type 1 or insulin-dependent diabetes: retinopathy leading to blindness, nephropathy leading to end-stage kidney disease, and neuropathy leading to loss of sensation, ulceration and amputation. The DCCT was designed to definitively answer whether a program of intensive therapy aimed at near normal levels of glycemia, when compared to conventional therapy aimed at maintenance of clinical well being, would affect the risk of onset and progression of these complications.

During the period 1983-1989, 1441 subjects were enrolled in the study, half the subjects assigned at random to intensive therapy and half to conventional therapy. All subjects were scheduled to be followed until the fall of 1993. However, the dramatic beneficial results of the trial lead to its termination one year early. The results were presented at the June 1993 meeting of the American Diabetes Association and the initial principal results paper appeared in the New England Journal of Medicine in September of that year (DCCT, 1993). The risks of the microvascular complications over the average of 6.5 years of follow-up were reduced by 26-63% with intensive versus conventional therapy. Intensive therapy, however, was associated with an excess weight gain of about 1 kg per year greater than that with conventional therapy, and a 3-fold greater risk of episodes of hypoglycemia where patients experience seizures and/or loss of consciousness, compared to conventional therapy (DCCT, 1995a).

Subsequent extensive statistical epidemiologic investigations showed that the risk of development of microvascular complications was principally determined by the lifetime exposure to hyperglycemia (DCCT, 1995b, 1996). However, the risk of hypoglycemia was weakly related to the level of glycemia, and more strongly related to intensive versus conventional therapy (DCCT, 1997). All total, more than 55 papers have been published that present the various methods and results of the DCCT. The complete DCCT bibliography can be obtained below.

The Harvard Health Letter named the DCCT the number one advance in medicine during 1993. In 1994, the DCCT Research Group was awarded the Charles H. Best Medal for distinguished service in the cause for diabetes, named for the co-founder of insulin. The DCCT has been used to set standards of care for diabetes mellitus worldwide (see links below).

As Coordinating Center, the Biostatistics Center participated in all aspects of the design, conduct and analysis of the study. In addition to Dr. Lachin and Ms. Cleary, statisticians who participated in the study included Jye-Yu Backlund, Oliver Bautista, Peter Gilbert, Max Halperin, David Kenny, James Knoke, K.K.Gordon Lan, Shuping Lan, and Desmond Thompson.

After the close of the DCCT, the NIDDK launched the study of the Epidemiology of Diabetes Interventions and Complications
(EDIC), for which the Biostatistics Center also serves as the Data Coordinating Center. Under the EDIC, the original DCCT cohort is being followed to assess the development of significant microvascular disease and the development of cardiovascular and other macrovascular diseases.

The DCCT Research Group (1997). Hypoglycemia in the Diabetes Control and Complications Trial. Diabetes45: 271-286.
The DCCT Research Group (1996). The absence of a glycemic threshold for the development of long-term complication: the perspective of the Diabetes Control and Complications Trial. Diabetes45: 1289-1298.
The DCCT Research Group (1995a). Adverse events and their association with treatment regimens in the Diabetes Control and Complications Trial. Diabetes Care18: 1415-1427.
The DCCT Research Group (1995b). The relationship of glycemic exposure (HbA1c) to the risk of development and progression of retinopathy in the Diabetes Control and Complications Trial. Diabetes44: 968-983.
The DCCT Research Group (1993). The effect of intensive treatment of diabetes on the development and progression of long-term complications in insulin-dependent diabetes mellitus. The New England Journal of Medicine329: 977-986.