Written by: Joseph Hansen
Graphics by: Josephine Ding
The year 2020 was one for the ages, albeit a rather negative one as we were seemingly faced with new challenges every day. The transition to virtual education remains despite the new year, and has caused several problems for students and faculty alike. A major issue arising from such a switch is the lack of energy and drive felt by many, as they are stuck staring at screens for numerous hours on end and late into the evenings.
“But why are we feeling so burned out”?
This question is not one that can be easily answered, as there are a wide array of conditions that students are exposed to. Overexposure to blue-light impacting sleep, however, may be one potential reason fuelling the widespread mental burn-out.
What is Blue-Light?
Human eyes function by allowing light to pass through to the back of the retina, which in turn is translated into the images that we see (Figure 1). Light exposure is the primary stimulus for regulating circadian rhythms, seasonal cycles, and neuroendocrine responses in many species, including humans (1). The term light itself is vague, as there are a multitude of different frequencies that form what is known as the visible electromagnetic spectrum. Colour of light is determined first and foremost by frequency (2). Everyday, we are exposed to light of varying frequencies, however not all light is complementary to our body’s naturally evolved processes (3). Simply stated, all light is not equal. In particular, blue wavelengths are the most potent of the visible spectrum, and tend to most strongly disrupt sleep-wake cycles, (aka circadian rhythm) (3,4). Although blue wavelengths are beneficial during the daytime (as there is evidence supporting that they boost alertness), this is conversely the case in the evening (3).
Figure 1: A simple diagram of the human eye demonstrating how light is taken in to produce the images that we see as our vision (5).
What is Circadian Rhythm and why is this affecting students?
Long before the invention of technologies like smartphones and laptops, the sun was the only major source of lighting, with evenings spent in relative darkness. As artificial light itself is a relatively recent invention, humans have not adaptively evolved for life with such exposure (1,3). Circadian rhythm is often referred to as our “biological clock” or “sleep-wake cycle”, and is defined as the “cyclic variation of physiological processes over a 24 hour cycle” (3,4). Although there is no definite circadian rhythm amongst humans, as it varies between individuals, the average length is approximately 24 hours and a quarter hours. To explain, the average “biological clock” for people regarding their sleep cycles is approximately 16-18 awake hours and 6-8 hours of sleep (6). Additional factors such as age must also be taken into account. As humanity has evolved technologically, once dark evenings have become illuminated. Unfortunately, more lumens (units for visible light) typically correspond to less sleep for many around the world, especially those who primarily operate in the virtual world (6). Even more unfortunate, however, are the consequences of inadequate rest.
How does Blue-Light Affect Sleep?
Regulation of sleep has been linked to a primary “circadian photoreceptor” that consists of fibres that connect directly from the retina to the suprachiasmatic nucleus (SCN) of the hypothalamus region of the brain (7). Studies have demonstrated that this photoreceptor does not respond to longer wavelengths of the visual spectrum (red, orange, yellow, green, etc) but does to shorter wavelengths such as blue light (1). These fibres make up a neural pathway known as the retinohypothalamic tract which is responsible for mediating circadian regulation by exposure to light (1). An additional segment of neuronal pathway extends from the SCN to the pineal gland (1). The pineal gland is a relatively tiny organ/neurochemical transducer located within the center of the brain (8,9). The gland is known to regulate production of hormones such as melatonin (1,8,9).
Figure 2 - The above diagram demonstrates how exposure to light results in inhibition of the pathway that allows the pineal gland to produce melatonin that supports sleep in mammals (9).
Through this joint neural-pathway (Figure 2), light and dark cycles are perceived through human eyes, which in-turn stimulates activity of the SCN, and subsequently entrains the regular rhythmic secretion of melatonin from the pineal gland (1,3,8). Since blue-light is known to disrupt this process and cause insomnia while other wavelengths do not, blocking blue-light can create a form of physiological darkness (3,7).
References
Brainard GC, Hanifin JP, Greeson JM, Byrne B, Glickman G, Gerner E, et al. Action spectrum for melatonin regulation in humans: evidence for a novel circadian photoreceptor. J Neurosci. 2001 Aug 15;21(16):6405–12.
Elert G. Color- The Physics Hypertextbook [Internet]. The Physics Hypertextbook. 2021 [cited 2020 Dec 13]. Available from: https://physics.info/color/
Shechter A, Kim EW, St-Onge M-P, Westwood AJ. Blocking nocturnal blue light for insomnia: A randomized controlled trial. J Psychiatr Res. 2018 Jan;96:196–202.
Nature Research. Circadian regulation - Latest research and news | Nature [Internet]. Nature Research. [cited 2020 Dec 13]. Available from: https://www.nature.com/subjects/circadian-regulation
GSU. Importance of Proper Eye Care | Health Services | Georgia Southern University [Internet]. Georgia Southern University- Health Services. 2019 [cited 2020 Dec 13]. Available from: https://auxiliary.georgiasouthern.edu/healthservices/eagle-eye-care/importance-of-proper-eye-care/
Harvard Health. Blue light has a dark side [Internet]. Harvard Health. [cited 2021 Jan 7]. Available from: https://www.health.harvard.edu/staying-healthy/blue-light-has-a-dark-side
Burkhart K, Phelps JR. Amber lenses to block blue light and improve sleep: a randomized trial. Chronobiol Int. 2009 Dec;26(8):1602–12.
Axelrod J. The Pineal Gland: A Neurochemical Transducer on JSTOR [Internet]. JSTOR. 1974 [cited 2020 Dec 13]. Available from: https://www.jstor.org/stable/1738874?casa_token=Wg1xZlrvof0AAAAA%3AJINvM-_aM_G62wVhTNdB7SXhT2_S02gVzAVErdcOkRNWkKq3os9lkRpamnGRF0WRydz7GlEpEHs0Ou0tOTu2EWypUI53sh8RtIZfD8KWmPh3Rkkkhhs&seq=1#metadata_info_tab_contents
Brzezinski A. Melatonin in humans. N Engl J Med. 1997 Jan 16;336(3):186–95.
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