1. Institute for Epidemiology, Social Medicine and Health System Research, Hannover Medical School, Carl-Neuberg-Street 1, 30625 Hannover, Germany
2. Institute for General Practice, Goethe-University Frankfurt, Theodor-Stern-Kai 7, 60590 Frankfurt am Main, Germany
3. Institute of General Practice and Family Medicine, Friedrich-Schiller-University Jena, Bachstraße 18, 07743 Jena, Germany