[1] Yonsei Univ, Coll Med, Dept Family Med, Severance Hosp, Seoul 120752, South Korea
[2] Chung Ang Univ, Dept Family Med, Med Ctr, Seoul 156756, South Korea
[3] Yonsei Univ, Coll Med, Dept Prevent Med, Seoul 120752, South Korea
[4] Yonsei Univ, Coll Med, Dept Biostat, Seoul 120752, South Korea