[1] Yonsei Univ, Coll Med, Dept Internal Med, Seoul 120752, South Korea
[2] Yonsei Univ, Coll Med, Inst Chest Dis, Seoul 120752, South Korea
[3] Yonsei Univ, Coll Med, Brain Korea Project Med Sci 21, Seoul 120752, South Korea
[4] Pochon Cha Univ, Coll Med, Dept Internal Med, Seoul, South Korea