Prognostic association of HbA1c and fasting plasma glucose with reduced kidney function in subjects with and without diabetes mellitus. Results from a population-based cohort study from Germany

Objective. To determine the risk for incident reduced kidney function (RKF) of subjects with pre-diabetes (impaired fasting glucose (IFG, 5.6-6.9 mmol/L)) or HbA(1c)-defined pre-diabetes (5.7%-6.4%) and to determine dose-response relationships of fasting glucose and HbA(1c) with RKF in subjects with manifest diabetes mellitus. Method. In a German population-based cohort, recruited 2000-2002 with ages 50-74 years, log-binomial regression was used to estimate relative risks (RR) with 95% confidence intervals (95%CI) and restricted cubic splines to plot dose-response relationships. Results. During 8 years of follow-up, 678 of 3538 study participants developed primary RKF. Although RKF risk factor prevalences and RKF incidences were higher in subjects with pre-diabetes than in subjects with normal FPG and/or HbA(1c) levels, an increased risk did not persist after adjusting for established cardiovascular risk factors (RR(IFG): 0.97 (95% Cl: 0.75-1.25) and RR(HbA(1c)-defined pre-diabetes): 1.03 (95% CI: 0.86-123)). In subjects with manifest diabetes, RKF risk increased linearly to a more than three-fold risk with increasing fasting glucose and HbA(1c) levels (at HbA(1c) > 6.4%). Conclusion. This study provides further evidence that pre-diabetes may not directly contribute to the development of kidney disease. Subjects with pre-diabetes might nevertheless profit from preventive efforts reducing their cardiovascular risk profile because cardiovascular and kidney disease share common risk factors. (C) 2013 Elsevier Inc. All rights reserved.