Background. Long-term microvascular and neurologic complications cause major morbidity and mortality in patients with insulin-dependent diabetes mellitus (IDDM). We examined whether intensive treatment with the goal of maintaining blood glucose concentrations close to the normal range could decrease the frequency and severity of these complications.

Methods. A total of 1441 patients with IDDM -- 726 with no retinopathy at base line (the primary-prevention cohort) and 715 with mild retinopathy (the secondary-intervention cohort) were randomly assigned to intensive therapy administered either with an external insulin pump or by three or more daily insulin injections and guided by frequent blood glucose monitoring or to conventional therapy with one or two daily insulin injections. The patients were followed for a mean of 6.5 years, and the appearance and progression of retinopathy and other complications were assessed regularly.

Eligibility Criteria:

• The major criteria for eligibility included insulin dependence, as evidenced by deficient C-peptide secretion; an age of 13 to 39 years; and the absence of hypertension, hypercholesterolemia, and severe diabetic complications or medical conditions. To be eligible for the primary-prevention cohort, patients were required to have had insulin dependent diabetes mellitus (IDDM) for one to five years, to have no retinopathy as detected by seven-field stereoscopic fundus photography, and to have urinary albumin excretion of less than 40 mg per 24 hours. To be eligible for the secondary-intervention cohort, the patients were required to have IDDM for 1 to 15 years, to have very-mild to moderate nonproliferative retinopathy, and to have urinary albumin excretion of less than 200 mg per 24 hours.