The Diabetes Control and Complications Trial (DCCT) was a randomized, controlled trial of individuals with type 1 diabetes mellitus (aged 13-39 years) comparing the effect of intensive blood glucose management to conventional management on diabetic outcomes over a mean 6.5-year follow-up. Subjects in general were in good health and had diabetes for 1 to 15 years.
Patients were stratified by the presence of retinopathy into a primary prevention cohort (no baseline retinopathy) and a secondary prevention cohort (mild retinopathy), and then randomized to either intensive insulin management consisting of three or more insulin doses per day to keep glucose levels as close to normal as possible or to conventional therapy consisting of standard insulin therapy to keep glucoses within accepted guidelines (A1c < 7.0).
For primary prevention, the adjusted relative risk of retinopathy was reduced by 76% (95% CI, 62%-85%) in the intensively treated group compared to the conventionally treated group. For secondary prevention, the risk of retinopathy progression was reduced by 54% (CI, 39%-66%) in the intensively treated group. In both cohorts, the reduction in risk increased with time and was not evident until 36 months into the treatment.
When the two cohorts were combined, intensive therapy reduced severe retinopathy and need for laser treatment by 47% and 51%, respectively, clinical neuropathy by 60% (CI, 38%-74%; p ≤ 0.002), microalbuminuria (p ≤ 0.002), and albuminuria (p < 0.04). Severe hypoglycemia was more common (62 versus 19), as were coma (16 versus 5) and emergency room admission (9 versus 4 cases per 100 patient-years) in the intensively managed group. No significant differences in mortality were observed between the two groups (7 intensive versus 4 conventional).
The DCCT resulted in a number of important recommendations. Intensive therapy with a goal of achieving glucose levels as close to the nondiabetic range as possible should be employed in most IDDM patients. Intensive therapy should be implemented in centers with the requisite nursing, dietary, behavioral, and clinical expertise to ensure safe and effective therapy. Although most diabetes in late life is not of the type 1 variety, this study provided important principles and hopes for improving the long-term prognosis for diabetes patients.
The most comprehensive study of type 2 diabetes to date has been the United Kingdom Prospective Diabetes Study Group.