1. Department of Otorhinolaryngology, Tokyo Metropolitan Geriatric Hospital, Itabashi-ku, Japan;
2. Department of Otolaryngology, Graduate School, Tokyo Medical and Dental University, Bunkyo-ku, Japan;
3. Department of Otorhinolaryngology, Showa University School of Medicine, Shinagawa-ku, Japan;
4. Department of Pathology, Tokyo Metropolitan Geriatric Hospital, Itabashi-ku, Japan;
5. Research Team for Geriatric Pathology, Tokyo Metropolitan Institute of Gerontology, Itabashi-ku, Japan