1. Department of Pediatrics; Hospital of Leverkusen; Leverkusen 51375 Germany
2. Department of Pediatrics; University of Leipzig; Leipzig 04103 Germany
3. Department of Pediatrics and Adolescent Medicine; Medical University Vienna; Vienna 1090 Austria
4. German Sport University; University of Köln; Köln 50933 Germany
5. Department of General Pediatrics, Neonatology and Pediatric Cardiology; University Children's Hospital Düsseldorf; Düsseldorf 40225 Germany
6. Institute for Epidemiology and Medical Biometry; University of Ulm; Ulm 89081 Germany