Renal outcome of type 2 diabetes in South Africa--a 12-year follow-up study

Previous studies of type 2 diabetes mellitus have indicated a benign renal outcome after long-term follow-up. The aim of this study was to determine how often renal failure due to diabetic nephropathy was a cause of death in patients with type 2 diabetes.

Prospective observational study of 59 South African patients with type 2 diabetes over a 12-year period. During the study repeated clinical evaluations were accompanied by measurements of serum creatinine, serum cholesterol, random blood sugar, and urine protein/creatinine ratios.

The mean duration of diabetes at the end of the study was 17.8 years. There was a wide variation in the time from clinical diagnosis of diabetes to macroproteinuria (mean 9.7 years, SD 5.9, range 0 - 21) and the rate of deterioration of renal function. This rate correlated with poor control of blood pressure, a glucose level of > 14 mmol/l, heavy proteinuria, a high retinopathy score, a body mass index of < 28 and the number of pack years of smoking. At the end of the study 47 patients (79.7%) had died. Of these deaths 17 (28.8%) were due to chronic renal failure.

In contrast to other studies we have shown that in a developing country renal failure in type 2 diabetic patients is a major cause of death. Determining the prognosis for an individual patient is difficult as there are wide ranges in the time of onset of proteinuria, the rise in serum creatinine and the time to ultimate progression to end-stage renal failure.