THE NATURAL COURSE OF MICROALBUMINURIA IN INSULIN-DEPENDENT DIABETES - A 10-YEAR PROSPECTIVE-STUDY

The purpose of this study was to describe the clinical course in patients followed right from the onset of microalbuminuria to the development of diabetic nephropathy. A 10-year prospective follow-up of 209 consecutive normotensive insulin-dependent diabetic patients with normal urinary albumin excretion (UAE <30 mg 24 h(-1)), age 34 (18-50) years and duration of diabetes 17 (10-30) years was performed. Twenty-four-hour urinary albumin excretion was measured every 4 months, glycated haemoglobin and supine blood pressure was measured annually. Two-hundred (96 %) patients completed 10 (range 5-10) years follow-up. Twenty-nine (15 %) patients developed persistent microalbuminuria (UAE 30-300 mg 24 h(-1)). Eight of these have progressed to nephropathy and one had died of diabetic nephropathy. Multiple stepwise logistic regression analysis demonstrated baseline urinary albumin excretion (p = 0.0016) and glycated haemoglobin (p = 0.0014) but not blood pressure as predictors of development of microalbuminuria within the following 10 years. The median annual increase in urinary albumin excretion was 27 (range 17-65) % in the 29 patients developing microalbuminuria. The median duration from onset of microalbuminuria to development of nephropathy was 7 years. The prevalence of patients receiving antihypertensive treatment (BP > 140/90 mmHg) increased from 10 % at onset of microalbuminuria to 45 % 4 years after onset of microalbuminuria. The prevalence of patients with proliferative retinopathy increased from 7 % at onset of microalbuminuria to 28 % 4 years after onset of microalbuminuria. The incidence of persistent microalbuminuria in normotensive insulin-dependent diabetic patients is 2 % per year, and development of persistent microalbuminuria is a strong predictor of overt nephropathy. Development of hypertension is frequent in the early course of microalbuminuria and treatment modalities for normotensive patients with microalbuminuria are urgently needed.