DCCT – Complications at 30 Years of Type 1 Diabetes

by nick wilkie

The Archives of Internal Medicine recently published (July 27, 2009) a paper on the rates of macrovascular (cardiovascular) and microvascular (eye, kidney, and nerve disease) complications 30 years after the diagnosis of type 1 diabetes, using data from the DCCT/EDIC studies. Results were compared for patients who had used tight glucose control early on versus those who had used conventional glucose control (“conventional” referring to the treatment standard in 1983, when the study began). The results add to the very strong body of evidence supporting tight glucose control and provide the most statistically valid estimates available for the projected complication rates of people with type 1 diabetes 30 years after their diagnosis.

the dcct/edic studies

Before we get into the outcomes, here is a bit of background on DCCT/EDIC (Diabetes Control and Complications Trial/ Epidemiololgy of Diabetes Interventions and Complications) (also see the link to the NIH website above): DCCT began in 1983 and sought to quantify the effects of tighter glycemic control on patients with type 1 diabetes. Participants were randomized to receive tight glucose control, in which patients either used an insulin pump or administered three injections of insulin per day (dosages adjusted by self monitoring of blood glucose (SMBG)), or they were placed in a conventional program, usually with two injections per day (using older, less stable insulins like Regular and NPH, not insulin analogs as they were not invented yet) that were not adjusted based on SMBG. Glycemic control, macrovascular complications, and microvascular complications were all monitored and recorded.

The assigned treatment regimens were continued until 1993, when the formal DCCT study period ended and the results were released. Patients in the intensive arm had an average A1c of about 7% over the study, while those in the conventional arm had an average of about 9%. The final results of the DCCT showed markedly lower levels of complications in the intensively controlled group, and so all of the patients involved were counseled to begin or continue intensive glycemic control.

When the DCCT ended, participants were invited to take part in an observational study called EDIC, which has been ongoing for the last 15+ years. This study has tracked the long-term effects of the treatment regimens initially assigned to the participants of DCCT. This follow-up has yielded data showing that, many years after the patients from both groups had switched to intensive treatment, microvascular and macrovascular complications continued to be far less frequent in the group that had undergone the early intensive therapy. This demonstrated a powerful “memory effect,” where early interventions can have health ramifications years later, regardless of the subsequent treatments.

30 years after diagnosis

In the present study, the authors looked at the macrovascular and microvascular outcomes of patients in EDIC based on their duration of diabetes, specifically 30 years after they were first diagnosed. It is important to note here that this does not mean 30 years after the study began, but 30 years after patients were first diagnosed.

The differences between the conventional and intensive treatment groups were dramatic. See the table below for the rates of proliferative retinopathy, nephropathy, and cardiovascular disease in the two groups. Of particular interest was the extremely low level of severe complications with less than 1% of the original intensive treatment group having developed vision loss or kidney failure requiring dialysis or transplantation or needing an amputation.

Clearly, tight control made a big difference in the long run. The rates of complications in both groups, but in particular in the intensive treatment group, are far lower than what has been reported in the past, which hopefully indicates a positive trend in treatment. However, the A1cs achieved in this study for the conventional group were a far cry from what is now recommended by the ADA and other professional groups. It is our hope that people being diagnosed with type 1 or type 2 diabetes today are now, as standard of care, given education on intensive management that will result in complication-free diabetes. We note that although this study doesn’t have direct implications for those with type 2 diabetes, the UKPDS study and its own follow up also showed the importance of intensive management. If you want to learn more, see the websites noted and ask your healthcare team about intensive management the next time you see them.