In the landmark randomized Diabetes Control and Complications Trial (DCCT), 1441 patients with type 1 diabetes received either intensive insulin therapy or conventional therapy; after 6.5 years, intensively treated patients had substantially lower glycosylated hemoglobin (HbA1c) levels (7.4% vs. 9.1%) and substantially fewer microvascular complications (retinopathy, nephropathy, neuropathy) than did conventionally treated patients. However, because enrollees were young (age range, 13–40) and follow-up was relatively short, the effect of intensive treatment on macrovascular complications remained unclear. Now, the research group reports outcomes from a long-term follow-up of DCCT — the Epidemiology of Diabetes Interventions and Complications (EDIC) study. After the DCCT concluded, most conventionally treated patients were switched to intensive treatment, and glycemic control was similar in all patients, regardless of their original group assignment, after 11 more years of follow-up (mean HbA1c levels, about 7.9% in both groups).
During the 17-year total follow-up of DCCT/EDIC, patients in the original intensive group experienced significantly fewer cardiovascular events than did patients in the original conventional group (0.4 vs. 0.8 events per 100 patient-years). Myocardial infarction, coronary revascularization, and confirmed angina were the most common endpoints. In multivariable analyses, improved glycemic control during DCCT accounted for much of the longer-term benefit.
The findings of this study finally confirm that intensive glycemic control can reduce risk for macrovascular complications in type 1 diabetics. A remarkable aspect of these results is that the intervention lasted for only 6.5 years, yet the beneficial effect persisted during another decade of follow-up. An editorialist notes, however, that applying these results remains difficult because of the obstacles to achieving tight control among children and adolescents with type 1 diabetes.
Reference:
1. The Diabetes Control and Complications Trial/Epidemiology of Diabetes Interventions and Complications (DCCT/EDIC) Study Research Group. Intensive diabetes treatment and cardiovascular disease in patients with type 1 diabetes. N Engl J Med 2005 Dec 22; 353:2643-53.
2. Cefalu WT. Glycemic control and cardiovascular disease -- Should we reassess clinical goals? N Engl J Med 2005 Dec 22; 353:2707-9.