1. Graduate Program in Epidemiology, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil
2. Otolaryngology and Head and Neck Surgery Department of Hospital de Clínicas de Porto Alegre, Porto Alegre, Brazil
3. Otolaryngology Department of Faculdade Medicina da Santa Casa de São Paulo, São Paulo, Brazil
4. Otolaryngology and Head and Neck Surgery Department of Complexo Hospitalar Santa Casa de Porto Alegre, Porto Alegre, Brazil
5. Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil