[1] Univ Tokyo, Grad Sch Med, Dept Pediat Surg, Bunkyo ku, Tokyo, Japan
[2] Natl Ctr Child Hlth & Dev, Dept Pediat Surg, Setagaya ku, Tokyo, Japan
[3] Univ Tokyo, Grad Sch Med, Dept Hlth Serv Res, Bunkyo ku, Tokyo, Japan
[4] Univ Tokyo, Sch Publ Hlth, Dept Clin Epidemiol & Hlth Econ, Bunkyo ku, Tokyo, Japan
[5] Tokyo Med & Dent Univ, Dept Hlth Policy & Informat, Grad Sch, Bunkyo ku, Tokyo, Japan
[6] Univ Tokyo, Grad Sch Med, Dept Pediat Surg, Tokyo, Japan
[7] Univ Tokyo, Dept Pediat Surg, Grad Sch Med, 7 3 1 Hongo, Bunkyo ku, Tokyo 1130033, Japan