1. Department of Otolaryngology University of Kansas Lawrence Kansas USA
2. Department of Epidemiology College of Public Health, UNMC, 984375 Nebraska Medical Center Omaha Nebraska USA
3. Department of Otolaryngology—Head and Neck Surgery College of Medicine, UNMC, 984395 Nebraska Medical Center Omaha Nebraska USA
4. Department of Biostatistics College of Public Health, UNMC, 984375 Nebraska Medical Center Omaha Nebraska USA