Awakening effects of blue-enriched morning light exposure on university students’ physiological and subjective responses

Abstract

We investigated physiological and subjective responses to morning light exposure of commercially available LED lighting with different correlated colour temperatures to predict how LED-based smart lighting employed in future learning environments will impact students. The classical markers of the circadian system (melatonin and cortisol), as well as the subjective perception of sleepiness, mood, and visual comfort, were compared. Fifteen university students underwent an hour of morning light exposure to both warm (3,500 K) and blue-enriched (6,500 K) white lights at recommended illuminance levels for classrooms and lecture halls (500 lux). The decline of melatonin levels was significantly greater after the exposure to blue-enriched white light. Exposure to blue-enriched white light significantly improved subjective perception of alertness, mood, and visual comfort. With regard to cortisol, we did not find a significant difference in the cortisol decrement between the two light conditions. Our findings suggest that the sensitivity of physiological and subjective responses to white LED light is blue-shifted. These findings, extending the already known effects of short-wavelength light on human physiology, reveal interesting practical implications. Blue-enriched LED light seems to be a simple yet effective potential countermeasure for morning drowsiness and dozing off in class, particularly in schools with insufficient daylight.

Blue-wavelength Light Therapy for Post-traumatic Brain Injury Sleepiness, Sleep Disturbance, Depression, Fatigue: A Systematic Review and Network Meta-analysis

“…However, a recent study in healthy young adults found that melatonin secretion was greater declined after the morning exposure to blue-enriched white light in comparison to warm white light [44]. Those physiological ndings were in line with the behavioral ndings that blue-enriched white light also decreased the participants' sleepiness and depressed mood to a greater extent.…”

Light-Dependent Effects of Prefrontal rTMS on Emotional Working Memory

“…Our findings of light-dependent rTMS responses, in combination with previous research regarding cognitive-emotional effects under blue light conditions [ 1 , 2 , 3 , 4 , 5 , 6 ], should be considered in future study designs using non-invasive brain stimulation. Natural daylight is on the blue end of the range of color temperatures, while an incandescent lightbulb emits lower warmer light [ 55 ].…”

“…Light is not only necessary for vision but also exerts a wide range of effects on other brain functions, including cognitive and emotional processing [ 1 , 2 , 3 , 4 , 5 , 6 ]. These non-visual effects of light are mediated by a specific type of photoreceptor, the intrinsically photosensitive retinal ganglion cells (ipRGCs) [ 7 ].…”

“…For example, during an auditory working memory task, less than 60 seconds of blue light exposure prompts the activation of supplemental prefrontal and thalamic brain regions associated with alertness and cognition as well as primary hubs of the default mode network [ 14 ]. Further to this, blue light exposure significantly improved subjectively [ 6 , 9 , 10 ] and objectively [ 15 ] measured alertness and vigilance, and accelerated relaxation processes after induced stress [ 16 ]. In contrast, green light has been shown to reduce arousal responses [ 1 , 5 ] and to decrease brain activity during working memory tasks [ 13 ].…”

Blue-wavelength light therapy for post-traumatic brain injury sleepiness, sleep disturbance, depression, and fatigue: A systematic review and network meta-analysis

“…The mechanisms of action of BWLT in reducing post-TBI depression and fatigue remain unknown. However, a recent study in healthy young adults found that morning exposure of BWLT was associated with a greater reduction of melatonin secretion compared with that of ALT [47]. Moreover, the BWLT also decreased the sleepiness and depressed mood to a greater extent than ALT.…”