[1] Hirosaki Univ, Grad Sch Med, Dept Gastroenterol & Hematol, 5 Zaifu Cho, Hirosaki, Aomori 0368562, Japan
[2] Hirosaki Univ, Grad Sch Med, Dept Community Med, 5 Zaifu Cho, Hirosaki, Aomori 0368562, Japan
[3] Hirosaki Univ, Grad Sch Med, Dept Social Med, 5 Zaifu Cho, Hirosaki, Aomori 0368562, Japan
[4] Aomori Gen Hlth Examinat Ctr, 2-19-12 Tsukuda, Aomori, Aomori 0300962, Japan
[5] Hirosaki Univ Hosp, Div Endoscopy, 52 Hon Cho, Hirosaki, Aomori 0368563, Japan