Cooperative Research Centre for Alertness, Safety and Productivity, Melbourne, Victoria, Australia.
School of Psychological Sciences and Monash Institute of Cognitive and Clinical Neurosciences, Faculty of Medicine, Nursing & Health Sciences, Monash University, Clayton, Victoria, Australia.
J Physiol. 2018 Jun;596(12):2381-2395. doi: 10.1113/JP275589. Epub 2018 Apr 6.
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.
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.
轮班工作非常普遍，并且与显著的健康影响有关。昼夜节律钟对变化的轮班周期的反应在个体之间存在很大的可变性。这种可变性的机制尚不清楚。我们检验了这样一个假设，即光-暗暴露是这种可变性的一个重要贡献因素；当与昼夜节律偏好相结合时，光暴露的相对时间解释了 71%的个体对夜班工作的昼夜节律相位反应的个体可变性。这些结果将推动针对轮班工人和其他弱势群体的昼夜节律紊乱的个性化管理方法的发展，从而有可能降低这些人群疾病风险的增加。
夜班工人的昼夜节律适应率差异很大。本研究调查了光暴露模式与夜间轮班工作后昼夜节律相位重置幅度之间的关系。在 21 名参与者（重症监护病房的护士和医务人员）中，使用 6-硫酸褪黑素在基线（白天/傍晚班次或休息日）和 3-4 个连续夜班后测量昼夜节律相位。相对于个体昼夜节律相位检查每日光暴露，以量化光相反应曲线（PRC）的相位延迟和相位提前部分的光强度。在三个或四个连续夜班后，相位偏移的方向和幅度在个体之间存在很大的可变性（平均相位延迟-1:08±1:31 h；范围从 3:43 h 延迟到 3:07 h 相位提前）。PRC 中光的分布与昼夜节律偏好的相对差异加上昼夜节律偏好，解释了相位偏移变异性的 71%。纳入这些因素的回归分析估计，在 85%的参与者中，相位偏移在±60 min 以内。没有参与者在三个或四个连续夜班后符合夜间工作部分适应的标准。我们的研究结果提供了证据，即发生的相位重置是基于个体相对于个体基线昼夜节律相位的光暴露模式。因此，在不了解昼夜节律相位的情况下，使用光疗法对轮班工作进行适应性推广的“一刀切”方法可能对所有个体都没有效果。
