Chronic Fatigue Syndrome in Korea Table 2. Point prevalence of prolonged fatigue and chronic fati- gue according to age and sex among patients aged ≥18 yr who attended to community-based eight primary care clinics in Korea (n=1,648) Age (yr) Men 18-29 30-39 40-49 50-59 ≥60 Women 18-29 30-39 40-49 50-59 ≥60 Subjects No. No. Prolonged fatigue (n=348) Prevalence (95% CI) No. Chronic fatigue (n=139) Prevalence (95% CI) 125 225 120 57 64 228 360 196 102 171 23 18.4% (11.6-25.2%) 10 8.0% (3.2-12.8%) 46 20.5% (15.0-26.0%) 13 5.8% (2.4-9.2%) 19 15.8% (9.3-22.3%) 8 6.8% (1.9-11.5%) 11 19.3% (8.9-29.7%) 5 8.8% (1.5-16.1%) 20 31.3% (19.9-42.7%) 9 14.1% (5.5-22.7%) 40 17.6% (11.6-22.8%) 15 6.6% (3.2-9.8%) 75 20.8% (14.3-27.3%) 33 9.2% (5.8-12.6%) 44 22.5% (16.6-28.4%) 18 9.2% (4.8-13.6%) 22 21.6% (13.5-29.7%) 13 12.8% (6.3-19.3%) 48 28.1% (21.3-34.9%) 15 8.8% (4.4-13.2%) Table 4. The major problems associated with medically explained chronic fatigue (n=112) No. (%) Causes 64 (57.1) Physical problems No. (%) 48 (42.9) Causes Psychosocial and psychiatric problems Stress Major depression Adjustment disorder Anxiety disorder Sleep disturbance Hwabyung Alcoholism Panic disorder 23 (16.6) 12 (8.6) 10 (7.2) 8 (5.8) 5 (3.6) 3 (2.2) 2 (1.4 ) 1 (0.7) Diabetes 9 (6.5) (poorly controlled) Asthma 9 (6.5) Chronic hepatitis 7 (5.0) Pulmonary tuberculosis 7 (5.0) Hypothyroidism 4 (2.9) Iron deficiency anemia 3 (2.2) Fatty liver 3 (2.2) Sleep apnea 2 (1.4) Chronic obstructive 2 (1.4) pulmonary disease Hyperthyroidism 1 (0.7) Herniated intervertebral 1 (0.7) disc All No. (%) represent prevalence among patients with medically explain- ed chronic fatigue. (95% CI 7.1-9.7%). Among the cases of CF, 80.5% were ex- plained CF, of which 42.9% (48 patients) were physical CF and 57.1% (64 patients) were psychological CF. The point prevalence of unexplained CF was 1.6% (95% CI 1.0-2.2%), and those of CFS (10 patients) and ICF (17 patients) were 0.6% (95% CI 0.2-1.0%) and 1.0% (95% CI 0.5-1.5%), respectively. Age-sex adjusted point prevalences of CF and CFS were 9.4% (7.9-1.09%) and 0.7% (0.3-1.2%) (Table 1). The prevalence of CF in men was higher in the age groups over sixty than in the other age groups, and that in women was the highest in the age group fifty to fifty-nine (Table 2). The percentage of patients complaining of prolonged fatigue or CF was relatively higher with aging (p=0.001) and edu- cated population (p=0.002) compared to that of no fatigue. Table 3. General characteristics of no fatigue, prolonged fatigue, and chronic fatigue groups (No. %) No fatigue Prolonged (n=1,161) fatigue (n=348) Chronic fatigue (n=139) Age (yr) 18-29 265 (22.8%) 63 (18.1%) 30-39 418 (36.0%) 121 (34.8%) 40-49 227 (19.6%) 63 (18.1%) 50-59 108 (9.3%) 33 (9.5%) ≥60 143 (12.3%) 68 (19.5%) Sex male 427 (36.8%) 119 (34.2%) female 734 (63.2%) 229 (65.8%) Education elementary 360 (31.0%) 94 (27.0%) middle school 491 (42.3%) 491 (42.3%) college 310 (26.7%) 130 (37.4%) Occupation unskilled/ 848 (73.0%) 210 (60.3%) semiskilled skilled 252 (21.7%) 117 (33.6%) professional 61 (5.3%) 21 (6.1%) Marital status unmarried 219 (18.9%) 45 (12.9%) married 899 (77.4%) 272 (78.2%) divorced 6 (0.5%) 8 (2.3%) others 37 (3.2%) 23 (6.6%) Alcohol intake 420 (36.2%) 129 (37.1%) Current smoker 213 (18.4%) 63 (18.2%) 25 (18.0%) 46 (33.1%) 26 (18.7%) 18 (12.9%) 24 (17.3%) 45 (32.4%) 94 (67.6%) 33 (23.7%) 61 (43.9%) 45 (32.4%) 81 (58.3%) 47 (33.8%) 11 (7.9%) 12 (8.7%) 105 (75.5%) 6 (4.3%) 16 (11.5%) 51 (36.8%) 30 (21.6%) 531 p-value 0.001 0.589 0.002 0.345 0.001 0.438 0.451 *p-value: by multivariated analysis adjusted for age, sex, education, occupation, marital status, alcohol intake, and current smoking status, ≥once per week. In addition, compared to those with a spouse, patients who were bereaved of, divorced by, or separated from the spouse tended to complain more of prolonged fatigue or CF (p=0.001) (Table 3). Among the cases of explained CF, 64 patients (57.1%) had psychosocial causes while 48 patients (42.9%) had physical causes. Stress was found to be the most frequent cause (23 patients, 16.6%), followed by of depression, adjustment dis- order, diabetes (uncontrolled), asthma, anxiety neurosis, chron- ic hepatitis, tuberculosis, etc. (Table 4). With regard to socio-demographic characteristics and per- sonal habits, the drinking rate was significantly higher in the group of physical CF than in the other three groups (p=0.018), and educational qualification was higher in the group of unex- plained CF than in that of explained CF (p=0.038). However, no statistically significant difference was observed in age, gen- der, occupational characteristics, and marital status among the groups. The frequency of stress was significantly higher in the group of psychological CF than in the other groups (p=0.002), and that of depression was significantly higher in the groups of psychological CF and CFS than in those of physical CF and ICF (p=0.001 in all) (Table 5). Patients with CFS patients showed high frequencies in all of the eight symptoms included in the diagnostic criteria for