Risk factors for the development of albuminuria and renal impairment in type 2 diabetes--the Swedish National Diabetes Register (NDR).

BACKGROUND: The aim of this study was to identify clinical risk factors associated with the development of albuminuria and renal impairment in patients with type 2 diabetes (T2D). In addition, we evaluated if different equations to estimate renal function had an impact on interpretation of data. This was done in a nationwide population-based study using data from the Swedish National Diabetes Register. METHODS: Three thousand and six hundred sixty-seven patients with T2D aged 30-74 years with no signs of renal dysfunction at baseline (no albuminuria and eGFR >60 mL/min/1.73 m(2) according to MDRD) were followed up for 5 years (2002-2007). Renal outcomes, development of albuminuria and/or renal impairment [eGFR < 60 mL/min/1.73 m(2) by MDRD or eCrCl > 60 mL/min by Cockgroft-Gault (C-G)] were assessed at follow-up. Univariate regression analyses and stepwise regression models were used to identify significant clinical risk factors for renal outcomes. RESULTS: Twenty percent of patients developed albuminuria, and 11% renal impairment; thus, ~6-7% of all patients developed non-albuminuric renal impairment. Development of albuminuria or renal impairment was independently associated with high age (all P < 0.001), high systolic BP (all P < 0.02) and elevated triglycerides (all P < 0.02). Additional independent risk factors for albuminuria were high BMI (P < 0.01), high HbA1c (P < 0.001), smoking (P < 0.001), HDL (P < 0.05) and male sex (P < 0.001), and for renal impairment elevated plasma creatinine at baseline and female sex (both P < 0.001). High BMI was an independent risk factor for renal impairment when defined by MDRD (P < 0.01), but low BMI was when defined by C-G (P < 0.001). Adverse effects of BMI on HbA1c, blood pressure and lipids accounted for ~50% of the increase risk for albuminuria, and for 41% of the increased risk for renal impairment (MDRD). CONCLUSIONS: Distinct sets of risk factors were associated with the development of albuminuria and renal impairment consistent with the concept that they are not entirely linked in patients with type 2 diabetes. Obesity and serum triglycerides are semi-novel risk factors for development of renal dysfunction and BMI accounted for a substantial proportion of the increased risk. The equations used to estimate renal function (MDRD vs. C-G) had an impact on interpretation of data, especially with regard to body composition and gender.