[1] Univ Tsukuba, Dept Resp Med, Inst Clin Med, Arai Clin, Tsukuba, Ibaraki 3058575, Japan
[2] Tohoku Univ, Sch Med, Dept Geriatr & Resp Med, Sendai, Miyagi 980, Japan
[3] Gifu Univ, Sch Med, Dept Internal Med 2, Gifu 500, Japan
[4] Univ Ryukyus, Fac Med, Okinawa, Japan
[5] Dokkyo Univ, Sch Med, Dept Internal Med, Tochigi, Japan