This is an early access version, the complete PDF, HTML, and XML versions will be available soon. Open AccessArticle by 1,*, 1, 1, 1, 1, 1, 2 and 1 1 Institute of Occupational and Social Medicine and Health Services Research, Medical Faculty, University Hospital Tuebingen, 72074 Tuebingen, Germany 2 Institute for Clinical Epidemiology and Applied Biometry, Medical Faculty, University Hospital Tuebingen, 72076 Tuebingen, Germany * Author to whom correspondence should be addressed.
