Significance of microalbuminuria in long-duration type 1 diabetes

OBJECTIVE - The value of microalbuminuria (MA) in predicting renal disease and premature mortality in longer duration type 1 diabetes is unclear. RESEARCH DESIGN AND METHODS - We followed 135 patients with long-standing type 1 diabetes (>30 years' duration) over a 7-year period, recording albuminuria and other clinical variables. Vital status was ascertained and cause of death was recorded. RESULTS - A total of 27 of 135 patients (20%) died during the follow-up period. Patients with MA (10 of 30, 33.3%) or proteinuria (5 of 6, 83.3%) at initial examination were more likely to die during follow-up than patients who had normal albumin excretion-at baseline (12 of 99, 12%; chi(2) for trend 21.9, P < 0.0001). The presence of abnormal albumin excretion and low BMI were independent risk factors of premature death. The causes of death were similar in patients with normal and abnormal urine albumin excretion. A total of 24.4% of initially normoalbuminuric survivors developed MA, and persistent proteinuria developed in 3.5%. Progressors had significantly higher albumin excretion rate at baseline compared with those who remained normoalbuminuric: 9.0 mug/min (3.8-18) vs. 4.0 mug/min (0.4-17.5); P < 0.001. A total of 21% of patients with MA at baseline reverted to normoalbuminuria, and persistent proteinuria developed in 32%. The likelihood of progression to persistent proteinuria was significantly greater in those with baseline MA compared with those with normal albumin excretion (P < 0.001). CONCLUSIONS - Even in long-standing type 1 diabetes of >30 years' duration, MA and proteinuria predict all-cause mortality. MA is a good predictor of persistent proteinuria.