. Daily expression of clock genes in whole blood cells in healthy subjects and a patient with circadian rhythm sleep disorder.

In the present study, the reliability and construct validity of the Japanese version of the Chalder Fatigue Scale was evaluated as a measure of severity of fatigue among young students in Japan. A healthy group comprised 27 Grade 6 primary school students and 28 Grade 1 junior high school students. The severely fatigued group were hospital outpatients with childhood chronic fatigue syndrome (n = 21). Principal components analysis with varimax rotation identified 4 factors which accounted for 63.2% of the total variance, as in the original English version. Internal consistency (Cronbach coefficient alpha) was .73, and test-retest reliability measured using Spearman rank correlation coefficient was .55. Scale scores of the healthy subjects were lower than those of the patients with childhood chronic fatigue syndrome. The reliability (alpha) and construct validity of the Japanese version of the scale among healthy students in Japan were satisfactory for research studies among healthy school students.

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The ability to divide one's attention deteriorates in patients with childhood chronic fatigue syndrome (CCFS). We conducted a study using a dual verbal task to assess allocation of attentional resources to two simultaneous activities (picking out vowels and reading for story comprehension) and functional magnetic resonance imaging. Patients exhibited a much larger area of activation, recruiting additional frontal areas. The right middle frontal gyrus (MFG), which is included in the dorsolateral prefrontal cortex, of CCFS patients was specifically activated in both the single and dual tasks; this activation level was positively correlated with motivation scores for the tasks and accuracy of story comprehension. In addition, in patients, the dorsal anterior cingulate gyrus (dACC) and left MFG were activated only in the dual task, and activation levels of the dACC and left MFG were positively associated with the motivation and fatigue scores, respectively. Patients with CCFS exhibited a wider area of activated frontal regions related to attentional resources in order to increase their poorer task performance with massive mental effort. This is likely to be less efficient and costly in terms of energy requirements. It seems to be related to the pathophysiology of patients with CCFS and to cause a vicious cycle of further increases in fatigue.

We examined relationships among fatigue, sleep quality, and effort-reward imbalance for learning in school children. We developed an effort-reward for learning scale in school students and examined its reliability and validity. Self-administered surveys, including the effort reward for leaning scale and fatigue scale, were completed by 1,023 elementary school students (grades 4-6) and 1,361 junior high school students (grades 7-9) at the end of 2006. Effort-reward imbalance for learning was associated with a high incidence of fatigue and sleep problems in elementary and junior high school students of both genders. A good relationship with family was associated with a low fatigue score in junior high school boys, and a good relationship with friends was associated with a low fatigue score in junior high school girls by multiple regression analysis. Fatigue score was associated with effort-reward imbalance and fatigue and quality of sleep in schoolchildren. Fatigue may lead to a decline in school performance, negative health outcomes, or refusal to attend school. These results suggest that it is desirable to consider social support, quality of sleep, and effort-reward imbalance when managing fatigue in school children.