Correlated colour temperature of morning light influences alertness and body temperature

Abstract

Though several studies have reported human alertness to be affected by the intensity and spectral composition of ambient light, the mechanism behind this effect is still largely unclear, especially for daytime exposure. Alerting effects of nocturnal light exposure are correlated with melatonin suppression, but melatonin levels are generally low during the day. The aim of this study was to explore the alerting effect of light in the morning for different correlated colour temperature (CCT) values, as well as its interaction with ambient temperature. Body temperature and perceived comfort were included in the study as possible mediating factors. In a randomized crossover design, 16 healthy females participated in two sessions, once under 2700K and once under 6500K light (both 55lx). Each session consisted of a baseline, a cool, a neutral and a warm thermal environment. Alertness as measured in a reaction time task was lower for the 6500K exposure, while subjective sleepiness was not affected by CCT. Also, core body temperature was higher under 6500K. Skin temperature parameters and perceived comfort were positively correlated with subjective sleepiness. Reaction time correlated with heat loss, but this association did not explain why the reaction time was improved for 2700K.

Assessment of visual fatigue under LED tunable white light with different blue components

“…Studies measuring physiological signals and perceived comfort showed that visual discomfort was higher under 6500 K of light compared with 2700 K for LED lights and the illuminances of S cones and melanopsin for 6500 K increased about 244% and 136%, respectively, which agrees with our findings. However, other studies using fluorescent lights that measured physiological signals showed that blue‐enriched light (6000 vs 2700 K) had no effects on comfort experience .…”

72‐5: Effect of LED Tunable White Light with Different Blue Components on Visual Fatigue

“…It agreed with that the visual acuity dropped off seriously and the symptom of dry eyes was more acute after the exposure of blueenriched white light. Studies measuring physiological signal and perceived comfort showed that visual comfort was higher under 2700K light compared with 6500K for LED lights [9]. The illuminances of S cones and melanopsin increased about 244% and 136% respectively for 6500K, and the result was agreed with ours.…”

Interactions between the perception of light and temperature

“…The current manuscript focuses on the interactions between the perception of light exposure and the perception of ambient temperature. Results of these studies on the alerting effects of light in relation to thermophysiological parameters (body temperatures) are reported elsewhere . The study design of both experiments was similar, consisting of two sessions with three time blocks with different ambient temperatures.…”

“…Results of these studies on the alerting effects of light in relation to thermophysiological parameters (body temperatures) are reported elsewhere. 17,18 The study design of both experiments was similar, consisting of two sessions with three…”