J Korean Med Sci 2005; 20: 529-34 ISSN 1011-8934 Copyright The Korean Academy of Medical Sciences Prevalence of Chronic Fatigue and Chronic Fatigue Syndrome in Korea: Community-Based Primary Care Study There have been many epidemiological and clinical researches on chronic fatigue (CF) and chronic fatigue syndrome (CFS) since the 1990s, but such studies have been quite limited in Korea. The aim of this study was to investigate the point preva- lence of CF and CFS in patients who visited community-based eight primary care clinics in Korea. The study subjects were 1,648 patients aged 18 yr and over who visited one of eight primary care clinics in Korea between the 7th and 17th of May 2001. The physicians determined the status of the subjects through fatigue-related questionnaires, medical history, physical examination, and laboratory tests. The subjects were categorized into no fatigue, prolonged fatigue, CF and then CF were further classified to medically explained CF (Physical CF and Psychological CF) and medically unexplained CF (CFS and idiopathic chronic fatigue). The point preva- lence of CF and CFS were 8.4% (95% CI 7.1-9.7%) and 0.6% (95% CI 0.2-1.0%). Medically explained CF was 80.5% of CF, of which 57.1% had psychological caus- es. The clinical characteristics of CFS were distinguished from explained CF. CF was common but CFS was rare in community-based primary care settings in Korea. Key Words : Prevalence; Epidemiology; Fatigue Syndrome, Chronic; Physicians, Family; Korea Cheol Hwan Kim, Ho Cheol Shin, Chang Won Won* Department of Family Medicine, Sungkyunkwan University School of Medicine, *Department of Family Medicine, College of Medicine, Kyung Hee University, Seoul, Korea Received : 8 March 2005 Accepted : 7 April 2005 Address for correspondence Cheol Hwan Kim, M.D. Department of Family Medicine, Kangbuk Samsung Hospital, Sungkyunkwan University School of Medicine, 108 Pyung-dong, Jongno-gu, Seoul 110-746, Korea Tel : +82.2-2001-2281, Fax : +82.2-2001-1280 E-mail : kchjp@hanafos.com INTRODUCTION It is known that fatigue and chronic fatigue (CF) are com- mon in patients visiting primary care institutions. Since the concept of chronic fatigue syndrome (CFS) emerged in West- ern countries in the 1980s, there have been many epidemio- logical and clinical researches on CF and CFS. The term and definition of CFS were first suggested by the Centers for Dis- ease Control and Prevention (CDC) of the U.S.A. in 1988 and new diagnostic criteria were established by CDC in 1994, which have been widely accepted until now (1, 2). The patho- physiologic mechanism of CFS is not clear yet. However, mul- tiple somatic and psychological symptoms as well as CF sig- nificantly disabling everyday life are distinct in patients with CFS. According to Western researches, CF disabling everyday life for over six months is found in 5-15% of patients visiting primary care institutions and 1-10% of general population; and the prevalence of CFS is as low as 0.5-2.5% of patients visiting primary care institutions and 0.2-0.7% of general population (3-6). In a recent study in Korea on 1,000 patients who visited the primary care center of a university hospital, the prevalence of CF was 11.4% and that of CFS 1.22% (7). However, there have been only a few epidemiological stud- ies on CF and CFS in Korea and no such study has been per- formed in general population or in those visiting primary care institutions in local communities. Thus we conducted this 529 study to estimate the prevalence of CF and CFS in patients visiting community-based primary care clinics in Korea. We also investigated the sociodemographic and clinical charac- teristics of CF and CFS. MATERIALS AND METHODS Subjects The study subjects were 18 yr old or older patients who visited one of eight community-based primary care clinics in Korea. This study was done between the 7th and 17th of May 2001. Among the eight community-based primary care clinics (all were Family Medicine), 5 were in Seoul, the metro- politan area, 1 in Gangwon-do, 1 in Chungcheong-do, and 1 in Jeju-do. Patients who refused to participate in the study or did not answer the questionnaires appropriately were ex- cluded, but there were no other specific exclusion criteria. During the study period, a total of 1,962 patients attended to eight primary care clinics and 1,648 of them participated in this study. Questionnaires All the participants were given self-reporting question- naires, and those who had difficulties in completing the ques-