1. Division of Rheumatology Philadelphia Veterans' Affairs Medical Center Philadelphia PA USA
2. Division of Rheumatology, School of Medicine University of Pennsylvania 8 Penn Tower Building, Philadelphia PA USA
3. Center for Clinical Epidemiology and Biostatistics University of Pennsylvania Philadelphia PA USA
4. Laboratory of Epidemiology and Population Sciences, Intramural Research Program NIA, NIH Bethesda MD USA
5. John's Hopkins School of Public Health Baltimore MA USA
6. Department of Medicine and Pediatrics Stanford University Palo Alto CA USA
7. Children's Hospital of Philadelphia Philadelphia PA USA
8. Division of Endocrinology and Diabetes Golisano Children's Hospital, University of Rochester Rochester NY USA