Nephropathy in persons with type 1 diabetes (formerly known as insulin-dependent diabetes) goes through stages—from microalbuminuria to overt proteinuria to end-stage renal disease. Previous studies have shown that the onset of microalbuminuria is related to glycemic control. Tight control has been shown to delay the onset of renal disease in persons with type 1 diabetes. However, evidence is unclear regarding the impact of tight glycemic control on the progression of renal disease after the onset of microalbuminuria. Warram and colleagues studied the dose-response relationship between exposure to hyperglycemia and progression of renal disease in patients with type 1 diabetes.

Type 1 diabetes patients at a major diabetes center were screened for microalbuminuria. Their urinary albumin excretion was classified as normal, microalbuminuria or overt proteinuria. Those who were found to have microalbuminuria were followed for four years with repeat evaluation of urine and glycosolated hemoglobin (HbA_1c) levels. Glycemic control was divided into four groups based on the level of HbA_1c. Patients with HbA_1c levels of less than 8 percent had an incidence rate of progression for renal disease of 1.3 per 100 person-years, while in those with a 10 percent or higher level, the rate was 6.7 per 100 person-years.

The authors conclude that the progression of nephropathy related to type 1 diabetes can be delayed by maintaining glycemic control with HbA_1c levels of less than 8.5 percent. This finding provides another reason to encourage patients with type 1 diabetes to strive for tight control of their blood sugar levels, even when there is early evidence of diabetic nephropathy.