Institute of Medical Biostatistics, Epidemiology and Informatics (IMBEI), University Medical Center Mainz, Johannes Gutenberg-University Mainz, Obere Zahlbacher Strasse 69, Mainz, Germany. weyer@uni-mainz.de.|Institute of Medical Biostatistics, Epidemiology and Informatics (IMBEI), University Medical Center Mainz, Johannes Gutenberg-University Mainz, Obere Zahlbacher Strasse 69, Mainz, Germany. binderh@uni-mainz.de.