Variations in 6-sulphatoxymelatonin excretion and oral temperature under a 12-hour shiftwork environment.

The aim of the present study was to follow the time-of-day variations in oral temperature and the excretion of a melatonin metabolite, 6-sulphatoxymelatonin (aMT6s), in individuals working fast-rotating, 12-h day and night shifts in a thermoelectric power station. Twenty-three male operators working on a 12-h-shift system (two successive days of the same shift: 0700-1900; 1900-0700, followed by two days off) were investigated. Oral temperature and aMT6s were measured at 4-h intervals on the second day shift and on the first and second night shifts. Clearly expressed "peaks" and "troughs" in aMT6s excretion and in oral temperature were found, indicating that a typical diurnal pattern of variation was preserved during fast-rotating, 12-h-shift work. The differences between the first and the second night shift in the examined parameters, particularly in aMT6s, can be attributed to the changes in sleep time between the two work shifts.