The effect of the colour temperature of morning light exposure on wellbeing

Abstract

This study investigates whether changing the colour temperature of indoor lighting can help improve the health of healthy adults’ emotions in life. Some studies have confirmed the effects of night-time lighting on alertness and sleepiness, but the jury is still out on what parameter range of light is used in the morning to have a lasting effect on mood changes. This study (N=16) investigated the effect of correlated colour temperature (CCT: 2500k, 5000k, 8500k, 18000k, 500lx) on individuals exposed to specific light sources for one hour in the morning. The scores are based on two levels psychological experience and physical performance. PANAS was used to perform mood scores as a psychological level of monitoring. The study found that except for the positive change of emotional PA-P under the condition of 8500k light in the morning, the results of other light parameters showed no noticeable activation effect. It can be seen from the score of PANAS-P that with the increase in colour temperature, PANAS-P has a positive effect. However, it will not improve because of the continuous increase in colour temperature. It will reach a relative peak at around 8500k, but because there is no more detailed classification of lighting parameters, it is impossible to get a precise change interval. Furthermore, a correlation between tympanic temperature and alertness was also found. 2500k light can make people feel sleepy, but there is a slight increase in tympanic temperature. This contradicts the claim that body temperature decreases during sleep. The guess might be that the body is not completely dormant, so the visually warm low colour temperature may affect the body. The data results for both PA-P and PA-N were less positive for participants at 2500k. In addition, at the level of physical changes, although the 8500k lighting parameters have a relatively positive impact on mood, the changes in tympanic temperature are not as stable as those under the other three sets of lighting parameters. A strong correlation was also found between tympanic temperature and KSS score under the four different light parameters, confirming that core body temperature and sleepiness level interacted with each other. Therefore, it is questionable whether universal lighting solutions are suitable for the use of lower CCT in daily life.