Characteristics of chronic fatigue syndrome in a Japanese community populationChronic fatigue syndrome in Japan

This study seeks to estimate the prevalence of chronic fatigue syndrome (CFS) and assess the characteristics of CFS in a community population in Japan using laboratory tests and questionnaires for lifestyle, fatigue states, and depression states. The design of this study is a cross-sectional observational study. The setting of this study is a medical health checkup program in a general hospital. This study was conducted with 1,430 Japanese (867 men and 563 women), 20 to 78 years of age. We classified participants who complained of fatigue according to the case definition of CFS proposed by the Centers for Disease Control and Prevention in the USA in 1994. Alcohol, caffeine, catechin and total polyphenol consumption, smoking status, sleep duration, and physical activity were evaluated using questionnaires. The prevalence of CFS was 1.0% (95% CI 0.5–1.6%) of a community population in Japan. Although various lifestyle factors of the participants with CFS were similar to those without chronic fatigue, average sleep duration was significantly shorter among the participants with CFS (5.5 ± 0.8 h) compared to those without chronic fatigue (6.3 ± 0.9 h, P < 0.001). Proportion at subjects having average sleep duration of less than 6 h was 64.3% among the participants with CFS in contrast to only 15.0% in those without chronic fatigue (P < 0.001). Among the eight case-defining symptoms, “Unrefreshing sleep” had high sensitivity and high specificity for screening CFS in Japanese population (92.9% and 87.8%, respectively). The average sleep duration was notably shorter in Japanese suffering from CFS. Further longitudinal study is needed to evaluate the possibility of extreme short sleep duration as a major cause of CFS in Japan.