by Ed Bryant
Recently, the authors of the Diabetes Control and Complications Trial (the "DCCT Group") published an article titled "Retinopathy and Nephropathy in Patients with Type 1 Diabetes Four Years after a Trial of Intensive Therapy," in the February 10, 2000 NEW ENGLAND JOURNAL OF MEDICINE.
Background: The DCCT and its British equivalent, the United Kingdom Prospective Diabetes Study (UKPDS) proved that for patients with diabetes mellitus, intensive therapy, "tight control" (meant to achieve near-normal blood glucose and glycosylated hemoglobin concentrations), significantly reduces the risk of diabetic complications, as compared with conventional therapy. To test whether these benefits persist, the authors "compared the effects of former intensive and conventional therapy on the occurrence and severity of retinopathy and nephropathy for four years after the end of the Diabetes Control and Complications Trial." Note: Participants in this study were all type 1, insulin- dependent diabetics, but the UKPDS' findings strongly suggest the same will be true for type 2 diabetes.
Methods: At the end of the DCCT (1993), the patients in the conventional- therapy group were offered the chance to switch to intensive therapy, and all patients' care was transferred to their own physicians. The occurrence of diabetic retinopathy was evaluated in 1208 of these patients during the fourth year after the DCCT ended, and nephropathy was evaluated with urine specimens obtained from 1302 patients during the third or fourth year, approximately half of whom were from each treatment group.
Results: The difference in the median glycosylated hemoglobin (HBA1c) values between the conventional-therapy and intensive-therapy groups during the years of the DCCT (average, 9.1 percent and 7.2 percent, respectively) narrowed during the follow-up (median during four years, 8.2 percent and 7.9 percent, respectively). Nevertheless, the proportion of patients with worsening retinopathy, proliferative retinopathy, macular edema, and the need for laser therapy, was lower in the intensive-therapy group than in the conventional-therapy group. The proportion of patients who had raised urinary albumin was significantly lower in the intensive-therapy group.
Conclusions: The reduction in the risk of progressive retinopathy and nephropathy that comes from "tight control" of blood sugars persists for at least four years, despite increasing hyperglycemia.
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