By the recent studies have been revealed that the strong light at night is one of the significant factors on the circadian rhythm. Disturbance in the secretion of melatonin develop as a consequence of biological rhythm's secretion. Secretion of melatonin is said that it involved in health risk and various diseases insomnia, depression, and obesity. Also insomnia risk often seen in elderly than young people. While exposure to light at night adversely affects the biological body, the exposure of sunlight has also been reported that gives a good effect on the organism of the elderly body. There is no doubt that in the modern house, lighting environment of the night has given a variety of effects on our bodies. However, it is not possible to separate the artificial lighting in the modern life. There is a need to go ring the alarm bells about the impact on the human body by providing a standard for lighting design.
The report addresses the action factors of the general lamps calculated by means of the quantification methods for circadian rhythm. The general lamps were the store-bought 46 LED and 12 fluorescent lamps. The ranges of the correlated color temperatures and the illuminances of lamps were about 2700-7300K and 100-500 lx. The quantification methods were DIN V5031-100 model, Rea's proposal model, Takahashi's proposal model and Enezi's proposal model. As a result, it was found that the correlated color temperatures and the illuminances from the lamps have influence on the action factors compared with kinds of lamps. This result suggested the action factors between the general LED lamps and the existed lamps were approximately-same as long as the correlated color temperatures and the illuminances between the lamps were similar.
Light exposure at night affects the human circadian system and is a possible cause of delayed sleep timing and circadian rhythm. It has been found that blue light has more impact on circadian rhythm and that even ordinary room light can suppress melatonin secretion at night. On the other hand, there is a large individual difference in light responsiveness. In order to recommend countermeasures and guidelines for light at night, it might be important to consider individual differences and the factors involved. In this paper, examples of inter- and intra-individual differences in the effects of light on circadian rhythm and melatonin secretion are introduced, and factors involved, including age, ethnicity, gene polymorphism and life style, are discussed.
Migraine is an illness with a throbbing pain on one side of the head, and is usually accompanied by photophobia towards sunlight or lighting. It is reported that this photosensitivity is caused by Intrinsically Photosensitive Retinal Ganglion Cell (ipRGC). At night, it is best to avoid light at the peak wavelength of ipRGC (480nm) that may cause migraine.
European lighting industry is developing and standardizing spectral efficiency functions that can be used to evaluate lighting conditions with respect to their potential to achieve eye-mediated, non-visual effects of light on humans. They are also promoting "human-centric lighting" that can give visual, physiological and emotional benefits to humans beyond the energy efficiency. German Institute for Standardization (DIN) is proactive in those actions. They have published design guidelines for biologically effective lighting. However, experts provide regulatory authorities, lighting manufacturers, designers and engineers with caution about biologically effective lighting design. It requires careful, informed consideration of the user context and environmental conditions as well as sufficient scientific knowledge about various effects of light on human physiology and behavior. This report describes those trends in standardization for quantifying non-visual effects of light on humans and in lighting applications.
It has been reported by only the knowledge about the action spectrum for melatonin suppression that prediction of the amount of actions by monochromatic light and polychromatic light cannot fully be performed. Although the hypothesis that an action spectrum has negative sensitivity, and the hypothesis that slope of a dose-response curve changes with the features of spectral distribution have been reported as a reason prediction is not enough, it has not fully been verified yet. It will be necessary for the user to know the condition that the action prediction including a comparison between the monochromatic light and the comparison between the polychromatic light is possible enough.
This article summarizes the newest knowledge related to effect of light on circadian regulation. There are several models each of which shows an action spectrum for light-induced melatonin suppression. However, these models are insufficient to calculate the combined effects of the intrinsically photosensitive retinal ganglion cells (ipRGC), rods and cones on melatonin suppression. Also in common environment, not monochromatic light sources but polychromatic light sources are used. Non-visual responses to a polychromatic light source may be different to that predicted from these models derived from the experiments using monochromatic light. At present, it can be recommended that high color temperature lighting at night should be avoided, especially for children.