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

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.

The Influence of Light Wavelength on Human HPA Axis Rhythms: A Systematic Review

“…For one study [45], where descriptive statistics were only available for the average of three time-points, the data are presented at the midpoint of the three timepoints in our figures. Two studies [40,46] provided insufficient descriptive statistics to enable a visual representation of their cortisol results, and thus their findings are described only qualitatively.…”

“…While the effects of light exposure parameters on melatonin levels and sleep behaviours have been systematically reviewed previously [28,39]), the impact on circulating cortisol (a key effector of circadian rhythms in peripheral tissues [3]) remains relatively less understood. Most notably, although it is accepted that bright light is more effective than dim light in altering cortisol secretions, it remains unclear whether light-induced changes in cortisol secretion are also dependent on the light spectrum, with some studies reporting a cortisol spectrum effect [10,[40][41][42] and others reporting spectrally dependent shifts in melatonin but not cortisol [43][44][45][46]. The light exposures tested in these studies included a range of combinations of circadian timing, duration, intensity and spectral distribution, presumably contributing to the different responses measured.…”

“…Cai et al [40] Bias within Included Studies tudies generally maintained a 'Probably Low' bias quality rating with respect posure characterization, outcomes, outcome measures reported, statistical d evaluation of confounding variables. Approximately 83% of the studies either a within-subject design or did not report if the participants or researchers were e study group allocation (questions 1-3 in the OHAT tool).…”

“…In this study, the night-time measures are expected to be affected by participant sleep deprivation. Two studies [40,74] reported insufficient descriptive statistics to enable calculation of percentage change in cortisol levels between conditions. Thus, their results were unable to be represented in this figure and are described in the manuscript text only.…”

Temperature Self-Adaptive and Color-Adjustable Smart Window Based on Templated Cholesteric Liquid Crystals

“…The spectrum plays an important part in biological clock regulation. For example, a blue crest between 460 nm and 480 nm was reported to show melatonin suppression effects, which was closely related to circadian rhythm regulation, and red light from 606 nm to 635 nm was likely to compensate for the melatonin suppression resulting from blue light [ 38 , 39 , 40 ]. The templated CLC with dynamic color was able to present automatic color change and active color adjustment, simultaneously blocking infrared radiation, which would be beneficial to biological clock regulation.…”