1 Division of Health and Nutrition Survey, Centers for Disease Control and Prevention, Cheongju-si, Korea.
2 Department of Health Policy and Management, Seoul National University College of Medicine, Seoul, Korea and Institute of Health Policy and Management, Seoul National University Medical Research Center, Seoul, Korea.
3 Division of Health and Nutrition Survey, Centers for Disease Control and Prevention, Cheongju-si, Korea, kwoh27@korea.kr.