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 Cock-groft-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, similar to 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 similar to 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.