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Temporal dynamics of circadian phase shifting response to consecutive night shifts in healthcare workers: role of light�dark exposure

Stone, J.E., Sletten, T.L., Magee, M., Ganesan, S., Mulhall, M.D., Collins, A., Howard, M., Lockley, S.W. and Rajaratnam, S.M.W. (2018) Temporal dynamics of circadian phase shifting response to consecutive night shifts in healthcare workers: role of light�dark exposure Journal of Physiology, 596 (12). pp. 2381-2395.

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Key points: Shift work is highly prevalent and is associated with significant adverse health impacts. There is substantial inter-individual variability in the way the circadian clock responds to changing shift cycles. The mechanisms underlying this variability are not well understood. We tested the hypothesis that light�dark exposure is a significant contributor to this variability; when combined with diurnal preference, the relative timing of light exposure accounted for 71% of individual variability in circadian phase response to night shift work. These results will drive development of personalised approaches to manage circadian disruption among shift workers and other vulnerable populations to potentially reduce the increased risk of disease in these populations. Abstract: Night shift workers show highly variable rates of circadian adaptation. This study examined the relationship between light exposure patterns and the magnitude of circadian phase resetting in response to night shift work. In 21 participants (nursing and medical staff in an intensive care unit) circadian phase was measured using 6-sulphatoxymelatonin at baseline (day/evening shifts or days off) and after 3�4 consecutive night shifts. Daily light exposure was examined relative to individual circadian phase to quantify light intensity in the phase delay and phase advance portions of the light phase response curve (PRC). There was substantial inter-individual variability in the direction and magnitude of phase shift after three or four consecutive night shifts (mean phase delay �1:08 ± 1:31 h; range �3:43 h delay to +3:07 h phase advance). The relative difference in the distribution of light relative to the PRC combined with diurnal preference accounted for 71% of the variability in phase shift. Regression analysis incorporating these factors estimated phase shift to within ±60 min in 85% of participants. No participants met criteria for partial adaptation to night work after three or four consecutive night shifts. Our findings provide evidence that the phase resetting that does occur is based on individual light exposure patterns relative to an individual's baseline circadian phase. Thus, a �one size fits all� approach to promoting adaptation to shift work using light therapy, implemented without knowledge of circadian phase, may not be efficacious for all individuals. © 2018 Monash University. The Journal of Physiology © 2018 The Physiological Society

Item Type: Article
Authors :
Stone, J.E.
Sletten, T.L.
Magee, M.
Ganesan, S.
Mulhall, M.D.
Collins, A.
Howard, M.
Rajaratnam, S.M.W.
Date : 2018
DOI : 10.1113/JP275589
Uncontrolled Keywords : circadian, light, melatonin, phase shift, shift work, adult, Article, circadian rhythm, controlled study, dynamics, female, health care personnel, health hazard, high risk population, human, intensive care unit, light dark cycle, light exposure, light intensity, male, medical staff, night shift, night shift worker, nursing, occupational hazard, personalized medicine, practice guideline, priority journal, risk assessment, risk reduction, time factor, adaptation, darkness, health care personnel, light, sleep, spatiotemporal analysis, Adaptation, Physiological, Adult, Circadian Rhythm, Darkness, Female, Health Personnel, Humans, Light, Male, Sleep, Spatio-Temporal Analysis
Depositing User : Clive Harris
Date Deposited : 17 Jun 2020 00:50
Last Modified : 17 Jun 2020 00:50

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