Further insight on the limits of success of glycemic control in type 1 diabetes.

Abstract

The successful extraction, purification, and use of insulin in the early 1900s led to greater survival in persons with type 1 diabetes as well as to a better understanding of the impact of diabetes on visual impairment and blindness (1). However, it was not until the completion of the Diabetes Control and Complications Trial (DCCT) that we fully understood the impact of the level of glycemia on the development of complications of diabetes, especially retinopathy (2). The DCCT was designed to assess the relationship between glycemic control and the development, progression, or amelioration of early vascular complications, such as retinopathy, in persons with type 1 diabetes. The trial recruited two groups of persons with type 1 diabetes: those with no complications of diabetes (the primary prevention group) and those with generally longer duration of diabetes and who had mild to moderate diabetic retinopathy and limited albumin excretion in the urine. The persons in these groups were randomly assigned to intensive or conventional diabetes therapy. The trial cohort was followed for a mean duration of 6.5 years. Development and progression of the severity of retinopathy were the primary end points. The trial was well designed and the outcome clearly demonstrated the beneficial effect of intensive glycemic control on the progression of diabetic retinopathy (2). This landmark trial informed and subsequently transformed the care of persons with type 1 diabetes. Patients in the general population were urged to self-monitor their levels of glycemia and to adjust their insulin doses accordingly (3,4). The functional impact seems …