Serum levels of retinol and other antioxidants for hearing impairment among Japanese older adults. - Michikawa T; Nishiwaki Y; Kikuchi Y; Hosoda K; Mizutari K; Saito H; Asakura K; Milojevic A; Iwasawa S; Nakano M; Takebayashi T (Journals of Gerontology Series A: Biological Sciences & Medical Sciences, 2009)