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Since the discovery of the intrinsically photosensitive retinal ganglion cells (ipRGCs) containing the light sensing photopigment melanopsin, there is growing interest in the research field of non-image forming (NIF) effects of light. Numerous studies have been already carried out to investigate NIF effects on humans. Some studies focus on circadian effects, while others investigate acute effects, such as an increase in attention. Although some results could be reproduced and are widely accepted in the scientific community, there are contradictory statements and a clear, holistic picture of NIF effects is still to be drawn. Since it is known that light can influence alertness, it is not surprising that researchers are also trying to find optimal workplace lighting, supporting employees and increasing well-being and productivity at the workplace. However, most studies use designs that are not easily transferable to real-life working conditions. The presented study is an approach to fill this gap by creating a study design that focuses on full-time daytime workers. Looking at the numerous studies that have been carried out to investigate acute NIF effects, it is conspicuous that results often differ significantly or even contradict, as shown by Souman et al. (2018). This can be explained by a great diversity in independent variables that are varied within these studies. In most studies the spectral composition and/or illuminance of light is altered. With the introduction of a new metric system to describe NIF effects of light by the CIE (CIE S 026/E:2018) parameters that depend on both of these quantities were introduced. In particular, the melanopic equivalent daylight illuminance (MEDI) has gained more and more interest. It describes how much daylight is needed to achieve the same melanopic stimulation as the current lighting scene considered. In 2020 Brown et al. showed, that this parameter can predict the magnitude of circadian responses for many lighting conditions. Therefore, we assume that this may also be possible for acute effects of light. In addition to the lighting properties, also temporal parameters are considered within this study. It could be shown that an increase in exposure duration can have similar effects as increasing illuminance (Dewan et al., 2011). The proposed study focuses on full-time daytime workers. Therefore, an exposure duration of 7.5 h is realized. In addition, all lighting scenarios fulfill the requirements for lighting at workplaces. Often studies include scenarios that are hardly realizable in real-life working situations. With this design we aim to investigate whether alternations between scenarios that could realistically be implemented on workplaces have an impact on the alertness of employees. |
