1 Department of Dysphagia Rehabilitation, Division of Gerontology and Gerodontology, Tokyo Medical and Dental University, Tokyo, Japan.
2 Department of Geriatric Medicine, National Center for Geriatrics and Gerontology, 7-430 Moriokamachi, Obu, Aichi, 474-8511, Japan. kskmaeda@ncgg.go.jp.