1. Doctoral Course of Health Science, Graduate School of Nursing, Oita University of Nursing and Health Sciences, 2944-9 Megusuno, Oita 870-1201, Japan
2. National Center for Child Health and Development, 2-10-1 Ohkura, Setagaya-ku, Tokyo 157-8535, Japan
3. Division of Nursing, Higashigaoka Faculty of Nursing, Tokyo Health University, 2-5-1 Setagaya, Setagaya-ku, Tokyo 152-8558, Japan
4. Department of Health Science, School of Health Science, Nippon Bunri University, 1727 Ichiki, Oita 870-0397, Japan