Effect of overtime work and insufficient sleep on postural sway in information-technology workers.

In Japan, death from overwork (“karoshi” in Japanese) is the focus of social concern. Extremely long work hours and deprivation of sleep exert vital exhaustion and mood changes, resulting in disease conditions such as depression and ischemic heart disease . As the prevention of diseases caused by heavy overtime schedules is a live issue in Japan, decisive and objective indicators are necessary for the early detection of irrecoverable damage to workers’ health. Young overtime workers, under forty, are often passed over by routine medical check-ups, nevertheless they have been suffering from shortened sleep and lack of effective rest. Especially information-technology workers in Japan are involved in extreme overwork beyond daytime working hours in order to compete in the global market. Detailed health assessments should be carried out with a view to identifying and implementing measures to relieve adverse health effects in overtime workers. The critical flicker fusion frequency (CFF) test is a suitable method for the measurement of short-term visual strain , however, few studies have indicated that CFF is sensitive as an objective measure of chronic fatigue. Therefore other convenient tools are required to detect exhausted workers at risk. Computerized static posturography has been used to examine balance function disorders, measuring displacements of the body’s center of pressure by the use of a force platform during static upright posture. The posturographic measurements are reportedly suitable for monitoring fatigue. Since continued insufficient sleep can lead to inability to concentrate, perceptual changes and dizziness, we performed a quantitative study using postural sway parameters as the disturbance stimulation of foot pressure movement in order to evaluate fatigued conditions of overtime workers at the early stage. The purpose of this study was to find medical evidence for the effects of extended working hours and short sleep time among younger workers under forty, and to recommend certain measures for their health assessment and control.