SLEEP PATTERNS AND FATIGUE SYMPTOMS IN PERMANENT NIGHT WORKERS AND SHIFT WORKERS

抄録

It is difficult to have day sleep of sufficient length after night work due to circadian rhythms and various conditions disturbing sleep. Thus, some night workers divide their day sleep into two or more parts, while the others have a single day sleep. It is of interest to know which sleep patterns would favor the recovery from fatigue. In this study, night workers were classified according to the frequency of the day sleep, i.e., those who usually had day sleep twice a day (split sleep group) and those who usually had a continuous day sleep (continuous sleep group). The two groups were compared concerning the number of fatigue symptoms complained of before and after work fatigue. Permanent night workers in the central market of Osaka and shift workers of an iron and steel works participated in this investigation. For the permanent night workers, the total duration of day sleep of the two groups was equally short (about 5.3 hr), but the number of fatigue symptoms of the continuous sleep group was more than the split sleep group, especially after work. In the case of the shift workers, however, the duration of day sleep of the split sleep group was longer than that of the continuous sleep group. It was suggested that day sleep split into two may be more effective for recovery than a continuous day sleep.