1. Clinical Research Center, Helen Hayes Hospital, Route 9W, West Haverstraw, NY 10993; Columbia University, New York, NY
2. Division of Epidemiology, Department of Health Research and Policy, Stanford University School of Medicine, Stanford, CA
3. Division of Epidemiology, Department of Health Research and Policy, Stanford University School of Medicine, Stanford, CA; Division of Preventive and Behavioral Medicine, University of Massachusetts Medical School, Worcester, MA
4. Department of Pediatrics, Stanford University School of Medicine, Stanford, CA
5. Geffen School of Medicine at UCLA, Los Angeles, CA
6. Department of Epidemiology, School of Public Health, University of Michigan, Ann Arbor, MI