Institute of Medical Biometry and Epidemiology, Philipps University Marburg, 35032 Marburg, Germany. dietter@med.uni-marburg.de|Institute of Medical Biometry and Epidemiology, Philipps University Marburg, 35032 Marburg, Germany. dietter@med.uni-marburg.de|Institute of Medical Biometry and Epidemiology, Philipps University Marburg, 35032 Marburg, Germany. dietter@med.uni-marburg.de|Institute of Medical Biometry and Epidemiology, Philipps University Marburg, 35032 Marburg, Germany. dietter@med.uni-marburg.de|Institute of Medical Biometry and Epidemiology, Philipps University Marburg, 35032 Marburg, Germany. dietter@med.uni-marburg.de|Institute of Medical Biometry and Epidemiology, Philipps University Marburg, 35032 Marburg, Germany. dietter@med.uni-marburg.de