Predictors of progression from normoalbuminuria to microalbuminuria in NIDDM.

OBJECTIVE: Our objective was to establish the clinical, genetic, metabolic, and immunologic risk factors for the progression of the albumin excretion rate (AER) in normoalbuminuric NIDDM patients. RESEARCH DESIGN AND METHODS: We recruited 108 NIDDM patients with normal AER after a diabetes duration of 9 years to participate in a prospective 9-year follow-up. In addition to conventional clinical and metabolic variables, we assessed microvascular (retinopathy, nephropathy, neuropathy) and macrovascular (coronary heart disease, peripheral vascular disease) diabetic complications, genetic markers (HLA genotypes), and organ-specific autoimmune markers, including islet cell antibodies. Multiple logistic regression was used to determine independent predictors of progression of AER. RESULTS: A total of 21 patients (19%) died during the follow-up. There was an overrepresentation of men (61 vs. 39%; P = 0.044) and smokers (55 vs. 27%; P = 0.01) in patients who progressed to micro- or macroalbuminuria versus those who did not progress. In addition, progressors had higher fasting plasma glucose (P = 0.002) and HbA1 (P = 0.0002) concentrations at baseline than did nonprogressors. Neuropathy was more often seen in progressors than in nonprogressors at baseline (53 vs. 16%; P = 0.0004). Frequency of HLA genotypes and autoimmune markers did not differ between progressors and nonprogressors. In a multiple logistic regression analysis, HbA1 (P = 0.0005) and a history of smoking (P = 0.011) were independent predictors of progression of AER. CONCLUSIONS: This study reemphasizes the importance of poor glycemic control and smoking as independent risk factors for progression of AER. Furthermore, development of micro- or macroalbuminuria in NIDDM was associated with neuropathy and male sex.