Natural history and prognostic factors of diabetic nephropathy in type 2 diabetes.

Background: The causes and mechanisms of increased mortality of patients with diabetic nephropathy are unclear, and its natural history is poorly understood. Aim: To evaluate risk factors for mortality in type 2 diabetic patients with nephropathy. Design:  Retrospective study of clinical and biochemical parameters in diabetic nephropathic patients and controls sampled from a secondary care register. Methods: We studied 170 type 2 diabetic patients (from 1987 to 1995) with nephropathy (proteinuria >0.5 g/24 h) and 170 non‐nephropathic patients. Follow‐up was until death or December 1997. Details of demographics, clinical and treatment history were obtained from medical records. Results: Mean follow‐up was 5.3 years. Of the patients with nephropathy at baseline, 63 (37%) died compared with 14 (8%) non‐nephropathic patients ( χ 2=53.8, p 2 g/24 h, 9.9 (7.3–13.5) per 100 patient‐years. A 36% (5–78%) excess risk of mortality was observed for each log unit increase in proteinuria. Multivariate Cox regression analyses confirmed a five‐fold excess risk for all‐cause and cardiovascular mortality in patients with nephropathy compared with those without. This was independent of other risk factors including baseline age [5% (1–8%)/year], creatinine [2.5 (1.12–5.6)/10 μmol/l] and glycaemic control (HbA1c) [15% (1–31%) per 1% rise]. Conclusions: Proteinuria is a potentially preventable and reversible risk factor associated with high mortality in type 2 diabetic patients. Prevention of the development of overt nephropathy and improvement in diabetes control may reduce mortality in these patients.