The Diabetes Control and Complications Trial (DCCT) was a multicenter, randomized clinical trial designed to compare intensive with conventional diabetes therapy with regard to their effects on the development and progression of the early vascular and neurologic complications of type 1 insulin-dependent diabetes mellitus. The DCCT study involved participants, ages 13 to 39, with type 1 diabetes and either no or minimal background retinopathy. Participants were required to have had diabetes for at least 1 year but no longer than 15 years.

Once enrolled, participants were randomized to receive standard therapy, consisting of not more than two injections of insulin per day, or intensive therapy, consisting of either subcutaneous insulin infusion by pump or at least three subcutaneous injections of insulin daily, targeting near-normal glycemia. Both groups received the same dietary management and education program. Blood glucose and hemoglobin A1c measurements were used as primary indicators of metabolic control.

The study sought to determine the effects of intensive versus standard diabetes therapy on the development and progression of the early vascular and neurologic complications of type 1 diabetes. Intensive therapy was aimed to maintain blood glucose concentrations close to the normal range in diabetic participants, which was hypothesized to decrease the development and progression of diabetic complications.

The primary outcome measure for the study was diabetic retinopathy, which was chosen because it can be reliably quantified and its rate of progression determined in a reasonable number of years. Blood glucose and hemoglobin A1c measurements were used as primary indicators of metabolic control. Other outcome measures included diabetic nephropathy, diabetic neuropathy, and cardiovascular events or their known or putative risk factors.

The DCCT study involved participants aged 13 to 39 years who had been diagnosed with diabetes for at least 1 year but less than 15 years, and who had no or early signs of diabetic retinopathy.

Please refer to the protocol for participant exclusion criteria.

The DCCT study found that intensive therapy showed beneficial effects on retinopathy, nephropathy, and neuropathy when compared with conventional therapy. The study showed that keeping blood glucose levels as close to normal as possible slows the onset and progression of the eye, kidney, and nerve damage caused by diabetes. Furthermore, the study demonstrated that any sustained lowering of blood glucose helped decrease the progression of complications, even if the participant had a history of poor control.