[1] Korea Univ, Coll Med, Dept Family Med, Ansan Hosp, Ansan, South Korea
[2] Sungkyunkwan Univ, Samsung Med Ctr, Dept Family Med, Sch Med, 81 Irwon Ro, Seoul 06351, South Korea
[3] Catholic Univ, Dept Biostat, Coll Med, Seoul, South Korea
[4] Soongsil Univ, Dept Stat & Actuarial Sci, Seoul, South Korea