Effects of Red Light on Circadian Rhythm: A Comparison Among Lamps With Similar Correlated Color Temperatures Yet Distinct Spectrums

Jianqi Cai,Ya Guo,Aiqin Luo,Wentao Hao,Shanshan Zeng,Xiangyu Qu,Shanshan Tang,Xin An

doi:10.1109/access.2021.3073102

Abstract

Blue crest between the wavelength of 460 nm and 480 nm was reported to present melatonin suppression effects, whereas effects of red light on circadian rhythm regulation remain unclear. Spectrum plays an important role in circadian rhythm regulation, yet a lot of researches focused on the correlated color temperature, although a correlated color temperature value corresponds to various possible spectrums. Here, we performed human factor experiments with 3 lamps on 17 participants, comprising 9 males and 8 females. Our results showed that spectrums with high blue intensity tended to cause abnormal regulations of melatonin and cortisol, while the abnormalities were likely to be compensated by the 606-635-nm red light, which was indispensable for the photo-biological effects concerning circadian rhythm regulation. Abnormal circadian rhythm regulation was also found to be influenced by the illuminance, as abnormalities were significant in 500 lux whereas they were likely to disappear in 250 lux, implying the existence of threshold doses to trigger abnormities concerning circadian rhythm regulation. Furthermore, circadian rhythm responses were distinct between males and females. Our work may have implications for the development of light source, as we suggest that lighting source designers should increase the 606-635-nm intensity for bed room luminaires to decrease melatonin suppression effects.

Highlights

Ambient light affects visual comfort [1], p2] and ocular safety [3], [4] through a series of neural and chemical processes
The 3 lamps were characterized by similar correlated color temperature of 5000K yet distinct spectrums: Lamp 1 with 467-nm blue crest, Lamp 2 with 453-nm blue crest, and Lamp 3 with double blue crests at 453 nm and 467 nm
Following the lighting of Lamp 1 and Lamp 3, significant abnormalities on circadian rhythm regulation appeared on participants with the illuminance of 500 lux, while in 250 lux abnormalities disappeared for females yet still existed for males

Summary

Introduction

Ambient light affects visual comfort [1], p2] and ocular safety [3], [4] through a series of neural and chemical processes. The characterization of ambient light is described by a set of photometric parameters, which correspond to the featured photo-biological (visual and non-visual) effects [5]–[7]. Light source development is accelerated by the abundant knowledge of photo-biological effects [12]–[14], studies on related issues are necessary and pressing. Light intensity is a significant photometric parameter due to the relation to power, and it is generally quantified as illuminance or brightness [15], [16], or the sum of photon energy [16]. Light color is determined by the wavelength distribution ( known as the spectral power distribution) and related to the visual and non-visual effects [17], [18]. Visual effects are generally reflected by ocular structural variations [19], while non-visual effects are usually characterized

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Conclusion