1. Department of Epidemiology and Public Health, Yale University School of Medicine, New Haven, Connecticut;
2. Department of Neurosurgery, Brigham and Women's Hospital, Boston, Massachusetts
3. Department of Epidemiology, M. D. Anderson Cancer Center, Houston, Texas;
4. Department of Community and Family Medicine, Duke University School of Medicine, Durham, North Carolina;
5. Departments of Epidemiology and Biostatistics, and
6. Neurological Surgery, University of California, San Francisco School of Medicine, San Francisco, California; and