Adaptation of the circadian rhythm of 6-sulphatoxymelatonin to a shift schedule of seven nights followed by seven days in offshore oil installation workers

Ocular Measures of Sleepiness Are Increased in Night Shift Workers Undergoing a Simulated Night Shift Near the Peak Time of the 6-Sulfatoxymelatonin Rhythm

“…While this may be a potential limitation to the research, the method is well-established in the literature as a suitable real-world assessment of circadian phase, of which the techniques and protocols used here have been applied successfully in several prior studies of shift workers on North Sea oil rigs, [45][46][47][48][49] in shift working nurses, [50][51][52] in shift workers living in Antarctica, 53,54 and in many clinical populations and experimental protocols. 35,[55][56][57][58] To assess the potential impact of light on aMT6s, in a previous study we compared aMT6s with urinary cortisol (which is much less confounded by light) in a subset of sighted individuals (n = 7) and found a strong relationship between the phase estimates (average Pearson r ± SD, 0.98 ± 0.01, p < 0.05).…”

Light Treatment and Circadian Adaptation to Shift Work

“…Nevertheless, the combination of bright light at night and morning goggles during the day induces the greatest phase delays 141,146) and can significantly improve daytime sleep quality 150) . Field studies on the night shift worker population support the efficacy of bright light treatment during the night shift 82,83,[151][152][153] , although some negative results have been reported 77) . Faster circadian adaptation of urinary 6-sulfatoxy-melatonin in the winter was reported with bright light in personnel working on Antarctic British Survey Base 85) .…”

“…These studies all indicate the heterogeneity of circadian adaptation to night shift work where progressive reduction of morning cortisol levels is consistent with some degree of circadian adaptation to a night oriented schedule 15,75) . Adaptive phase delays of cortisol and melatonin rhythms to an atypical work schedule are possible 76) and are influenced by the pattern of light and darkness exposure 17,75,[77][78][79][80][81][82][83][84] . The pattern of light exposure in night shift workers who spontaneously adapt to the shift work schedule are notable for the stability of sleep times 13) , limited exposure to bright sunlight in the morning 17) , brighter light during shift hours combined with sleep times in darkness 81) , and limited exposure to light throughout the day in Antarctic studies 85) .…”

Melatonin as a Biomarker of Circadian Dysregulation

“…Using a cosinor analysis to estimate phase position, they reported individual variability in adaptation to nightshift work, with 5 participants showing a phase delay, 3 a phase advance, and the remaining 22 showing no phase shift (the timing of their melatonin secretion was typical of a dayshift worker). In a study involving offshore oil workers employed in a weeklong alternating shift schedule (one week nights, one week days), Gibbs et al (127) reported adaptation to the nightshift schedule via a delay of aMT6s at the end of the week of nightshifts. In another study of offshore oil workers employed in a 2-week alternating shift schedule (two weeks of days, two weeks of nights), Barnes et al (128) reported similar results, with the delay of aMT6s occurring during the first week of the nightshift.…”