SLEEP-WAKE BEHAVIOR WHILE ON-DUTY AND OFF-DUTY FOR SHIFT WORKERS IN THE IRON AND STEEL INDUSTRY USING WRIST ACTIGRAPH

Abstract

The purpose of this study was to investigate the effects of sleep/wake behavior for shift workers in the iron and steel industry using wrist actigraphy for 59 male workers on a continuous full-day 3-team 3-shift system of backward rotation including on-duty and off-duty periods. The wrist actigraphy data was recorded for 15 days (one shift cycle) for each subject. The sleep length at home during night shift decreased significantly as compared to the morning or evening shifts. The doze length during night shift decreased significantly in Steel Manufacturing and Rolling Processes as compared to Forwarding of Products, Machine Maintenance and Field Management Sections. However, the sleep length at home during the off-duty period increased significantly. The percentage of doze length per total night shift in Steel Manufacturing, Rolling Processes, and the other three sections of job was 20.4%, 16.0%, and about 50%, respectively. The doze length during the night shift and the sleep episodes at home for the above 50 year old age group increased significantly as compared to the below 50 year old age group. From these results, we discussed the role of ‘taking-dozes’ for shift workers during the burden of night shift and the increased difficulty in continuing their job.