1. Graduate School of Gerontology, J. F. Oberlin University, Machida-city, Tokyo 194-0294, Japan
2. Faculty of Health and Medical Sciences, Tsukuba International University, Tsuchiura-city, Ibaraki 300-0051, Japan
3. The Jikei University School of Nursing, Chofu-city, Tokyo 182-8570, Japan
4. School of Nursing, Osaka City University, Osaka-city 545-0051, Japan