1. Department of Epidemiology, Quintiles IMS, D-60598 Frankfurt, Germany
2. Faculty of Medicine, University of Paris V, 75006 Paris, France
3. Department of Gynecology and Obstetrics, Philipps University of Marburg, D-35037 Marburg, Germany
4. Department of Otorhinolaryngology, Head and Neck Surgery, Solingen Municipal Hospital, D-42653 Solingen, Germany