1. Division of Nephrology, Department of Internal Medicine, University Medical Center Groningen and University of Groningen , Groningen , The Netherlands
2. Division of Nephrology and Hypertension, Department of Medicine, Mayo Clinic , Rochester, MN , USA
3. Department of Quantitative Health Sciences, Mayo Clinic , Rochester, MN , USA
4. Department of Epidemiology, University Medical Center Groningen and University of Groningen , Groningen , The Netherlands