[1] Univ Tsukuba, Fac Med, Dept Hlth Serv Res, Tsukuba, Ibaraki, Japan
[2] Natl Inst Populat & Social Secur Res, Dept Empir Social Secur Res, Chiyoda Ku, Tokyo, Japan
[3] Fukushima Med Univ, Fac Med, Radiat Med Sci Ctr Fukushima Hlth Management Surv, Off Informat Management & Stat, Fukushima, Japan
[4] Waseda Univ, Fac Polit Sci & Econ, Shinjuku Ku, Tokyo, Japan