Light and the circadian system in humans

光不仅仅是视觉所必需的。光也有许多非视觉的生物功能，这就是为什么控制光照可以用来治疗一些情绪障碍（如冬季抑郁症）和睡眠觉醒障碍（如睡眠时间异常）。相反，不适当的光照时间可能会产生“毒性”效应，并与各种疾病的发展有关。我们NSERC研究项目的目的是了解光是如何被感知、解释和用于非视觉功能的，特别是对我们内部生物钟的调节，即昼夜节律系统。与该领域对人类受试者的大多数研究相反，我们研究的是24小时调制光的影响，而不是光刺激的影响，我们将现实生活中的实地研究与受控的实验室测试相结合。未来5年计划开展两个主要研究项目。第一个项目将重点关注夜间工人在白天“错误”时间暴露在光线下的影响。其目的是确定与夜班工人褪黑激素分泌减少有关的光照特征，因为褪黑激素分泌减少与癌症风险增加有关。夜班工人将佩戴一个小型监测器来测量他们的光照，并收集48小时的尿液来评估他们的褪黑激素分泌。我们会评估因夜间工作的光照强度和日照时间的季节性变化而造成的不同光照模式的影响。第二个项目将集中在自然早睡或晚睡的正常受试者身上。这些个体的生物钟根据外部昼夜周期进行不同的调整，这使得它们成为研究光在昼夜生理中的作用的有趣模型。由于光的影响不仅取决于光的暴露，也取决于光的灵敏度，我们计划在这些科目中同时测量这两个因素。我们将开发新的方法来测量光敏度，特别是适应于光感知的非视觉系统的评估。我们希望我们的研究结果将有助于基于控制光暴露和操纵非视觉光敏感性的新的预防和治疗策略的发展。

Light is not necessary only for vision. Light also has many non-visual biological functions, which is why controlled light exposure can be used to treat some mood disorders (like winter depression) and sleep-wake disorders (like abnormal sleep timing). Conversely, inappropriate timing of light exposure can have "toxic" effects and be involved in the development of various disorders. The aim of our NSERC research program is to understand how light is perceived, interpreted, and used for non-visual functions, especially for the regulation of our internal biological clock, the circadian system. Contrary to most research on human subjects in this field, we are studying the effects of light modulated over the 24-h, instead of the effects of light stimuli, and we combine real-life field studies with controlled laboratory testing. Two main research projects are planned for the next 5 years. The first project will focus on the effects of light exposure at the "wrong" time of day in night workers. The aim is to identify the characteristics of light exposure that are related to decreased melatonin production in night workers, because decreased melatonin production has been associated with increased risks of cancer. Night workers will wear a small monitor to measure their light exposure, and they will collect their urine for 48 h to assess their melatonin production. We will assess the effects of different patterns of light exposure due to light intensity during night work, and to seasonal variations in daylight duration. The second project will focus on normal subjects with naturally early or late sleep schedules. The biological clock of these individuals is adjusted differently to the external day-night cycle, which makes them an interesting model to study the role of light in circadian physiology. Since the effects of light depend not only on light exposure but also on light sensitivity, we plan to measure both in these subjects. We will develop new methods to measure light sensitivity, specifically adapted to the assessment of the non-visual system of light perception. We hope that the results of our studies will contribute to the development of new prevention and treatment strategies based on controlled light exposure and manipulations of non-visual light sensitivity.