Time as a Risk Factor in Diabetic Nephropathy

Eighteen individuals with IDDM (type I) and diabetic nephropathy in whom the initial glomerular filtration rate (GFR) was reduced but not below 60 ml/min per 1.73 m² were observed for an average of 3 yr. The rate of further decline of GFR was found to range between −2 and 21 ml/min/yr. The duration of diabetes until the GFR was first found to be reduced varied between 14 and 33 yr and was not correlated to the ensuing rate of decline in GFR (r = −0.13). In 10 individuals who developed uremia 40 yr or more after onset of IDDM, the development of persistent ptoteinuria was followed by hypertension and increased serum creatinine 2 yr later and by terminal uremia after an average of 8 yr. This is also the normal time span for individuals who develop terminal uremia after shorter duration of diabetes. We conclude that the course of clinical diabetic nephropathy is not more favorable in individuals with late onset of this complication and that there is no point at which a person with diabetes can be considered to be spared from developing diabetic nephropathy.