Changes in the Concentration of Urinary 6-sulphatoxymelatonin during a Week of Simulated Night Work

Abstract

The aim of the study was to examine the adaptation of participants to a common night work schedule using urinary 6-sulphatoxymelatonin (aMT6s) concentration as the circadian phase marker. Fifteen adults (7 male, 8 female, age = 21.9 yr) spent nine consecutive nights in the laboratory, including: (i) adaptation sleep, (ii) baseline sleep, and (iii) seven simulated night shifts (23:00-07:00 h) followed by daytime sleep. During the baseline and daytime sleeps, participants collected urine samples which were subsequently assayed for aMT6s. The concentration of aMT6s in urine for the first three day sleeps was significantly lower than for the baseline sleep, but there was no difference in aMT6s concentrations between any of the last three day sleeps and the baseline sleep. The data indicate that people may adapt to a pattern of work that includes seven consecutive night shifts if they adhere to a fixed sleep schedule, if their exposure to morning sunlight is minimised, and if they are provided with an ideal sleep environment.

Melatonin as a Biomarker of Circadian Dysregulation

“…More recently, Roach et al (120) conducted a simulated nightshift work study in which participants ''worked'' 7 consecutive 8-h shifts and reported a mean phase delay of 5.5 h by night 7 using salivary melatonin measurements to detect the phase shift. A later study by this same investigative team reported similar results using urinary aMT6s levels to assess phase delay (121).…”

The Effect of Night-Shift Work on the Level of Urinary 6-Sulphatoxymelatonin in Men Over Five Days

“…Normally, phase delay happens after multiple night in a row, in which the central sleep-wake cycle adapted to being awake at night and lead to delay in the time of maximum secretion of urinary 6-sulphatoxymelatonin (29). Thus, the increased level of urinary 6-sulphatoxymelatonin at the end of the fifth nightshift may be explained by the effect of phase delay, when the peak of nocturnal melatonin secretion was captured, a hypothesis that accords with previous studies that have reported that phase delay (adaptation) seldom happens during the first three days of night-shift work (29,34). Moreover, the timing of peak melatonin production can vary from one individual to another, as demonstrated in a previous study that found evidence for a large variation between individuals (35).…”

Diurnal Urinary 6‐Sulfatoxymelatonin Levels among Healthy Danish Nurses during Work and Leisure Time

“…For example, they do not have a corresponding increase in the excretion of 6-sulfatoxymelatonin during the following sleep period, which is linked to more symptoms of sleep disturbances and fatigue (Burch et al, 2005). This effect, however, may wear off: Roach et al (2005) showed that the urinary excretion of 6-sulfatoxymelatonin was reduced during the first three daytime sleeps in a simulated night work schedule, but there was no significant reduction in the excretion of 6-sulfatoxymelatonin in the urine thereafter, indicating a shift in the circadian rhythm.…”