1. School of Medicine, University of California–San Francisco, San Francisco, California, USA
2. Department of Otolaryngology–Head and Neck Surgery, Stanford University, Stanford, California, USA
3. Division of Pediatric Otolaryngology, Department of Otolaryngology–Head and Neck Surgery, University of California–San Francisco, San Francisco, California, USA
4. Department of Epidemiology and Biostatistics, University of California–San Francisco, San Francisco, California, USA