1. Department of Epidemiology, University Medical Center Groningen, University of Groningen, 9713 GZ Groningen, The Netherlands
2. Department of Preventive Medicine, Shantou University Medical College, No. 22, Xinling Road, Shantou 515041, China
3. Department of Internal Medicine, Division of Nephrology, University Medical Center Groningen, University of Groningen, 9713 GZ Groningen, The Netherlands