Risk factors for development of incipient and overt diabetic nephropathy in type 1 diabetic patients: a 10-year prospective observational study.

OBJECTIVE To evaluate prospectively putative risk factors for development of microalbuminuria and macroalbuminuria in type 1 diabetes. RESEARCH DESIGN AND METHODS Prospective observational study of a cohort of type 1 diabetic patients followed in the outpatient clinic at Steno Diabetes Center for < or =10 years (median 9 years). We followed 537 patients aged > or =18 years with type 1 diabetes, with duration of diabetes > or =5 years, with normoalbuminuria (urinary albumin excretion rate < or =30 mg/24 h), and who were not taking antihypertensive medication. Risk factors for development of microalbuminuria and macroalbuminuria were evaluated. RESULTS The mean progression of urinary albumin excretion rate was 7.6% (SE 0.8) per year. During follow-up, 134 patients (25%) progressed to persistent microalbuminuria or macroalbuminuria (>30 mg/24 h in two of three consecutive urine samples). Cox multiple regression analysis using baseline values of putative predictors of progression showed the following significant predictors of progression from normoalbuminuria to microalbuminuria or macroalbuminuria: baseline log urinary albumin excretion rate 2.63 (relative risk; 95% CI 1.65-4.19), HbA(1c) 1.13% (1.04-1.23), presence of any retinopathy 1.90 (1.26-2.88), and smoking 1.61 (1.11-2.33). Sex, duration of diabetes, arterial blood pressure, serum creatinine, height, and social class were not risk factors. CONCLUSIONS Our study suggests that several potentially modifiable risk factors predict the development of microalbuminuria and macroalbuminuria in type 1 diabetic patients.