Evolution, Risk Factors, and Prognostic Implications of Albuminuria in NIDDM

OBJECTIVE: To study the cumulative incidence of albuminuria and its determinants in NIDDM patients and nondiabetic subjects from the diagnosis and impact of albuminuria on cardiovascular mortality. RESEARCH DESIGN AND METHODS: We performed a 10-year prospective observational study of 133 well-characterized middle-aged patients with newly diagnosed NIDDM and 144 control subjects. Both groups were examined at baseline and after 5 and 10 years. Urinary albumin excretion was determined from timed 24-h (baseline and 5-year examinations) or overnight samples (10-year examination). Microalbuminuria was defined as urinary albumin excretion of 30-300 mg/24 hr or 20-200 micrograms/min, with the higher values considered as macroalbuminuria. RESULTS: The cumulative incidence of micro- and macroalbuminuria increased sharply after 5 years in NIDDM patients (baseline: 18.2 and 3.0%; 5 years: 18.9 and 1.8%; and 10 years: 33.0 and 10.2%) but markedly less in control subjects (baseline: 1.4 and 0%, P < 0.001 for diabetic patients vs. control subjects for any albuminuria; 5 years: 6.0 and 0.8%, P < 0.01; 10 years: 11.9 and 0.8%, P < 0.001). The most important determinant of the development of albuminuria was the metabolic control of diabetes in NIDDM patients during the follow-up, whereas in nondiabetic subjects, the development of albuminuria was related to elevated blood pressure and fasting insulin levels. Baseline and 5-year albuminuria predicted subsequent cardiovascular mortality in diabetic patients, even when adjusted for multiple risk factors. The risk of cardiovascular death in NIDDM patients increased by simultaneous occurrence of hyperinsulinemia and albuminuria. CONCLUSIONS: The frequency of microalbuminuria in patients with NIDDM increases sharply with the duration of diabetes. Chronic hyperglycemia is the main risk factor for microalbuminuria in diabetic patients. Microalbuminuria accompanied by hyperinsulinemia is a powerful predictor of cardiovascular death in NIDDM patients.