Before the invention of technology and artificial lighting, natural sunlight was the main source of lighting, and when the sun set, evenings were mainly spent in darkness. This was the most natural regulation of the human circadian rhythm. Blue light is emitted from LED lights, computer screens, smartphone screens, television, and the sun. With the invention of artificial lighting and modern-day technology, humans spend their evenings illuminated by blue light, dysregulating the human biological clock. This clock is the human circadian rhythm. This is where the problems begin to arise. The exposure of artificial light at night tricks the human brain into believing that it is daytime, because blue light essentially tells the brain that it needs to be awake and alert. Blue light communicates with the hypothalamus, telling it that it needs to be awake, shutting off the production of melatonin. The brain cannot distinguish between artificial and natural blue light. This makes the brain believe that it needs to stay awake, suppressing mechanisms to initiate sleep, therefore dysregulating the natural cycle of sleep-wake time.
Light of any kind is known to suppress the secretion of melatonin in the brain, but blue light specifically suppresses this secretion at a more powerful rate. Blue light wavelengths are the most potent wavelengths of the visible electromagnetic spectrum regarding circadian rhythm. During the day, blue light is considered beneficial as it boosts attention, mood and increases reaction time. The timing, as well as longevity of lightness and darkness greatly affect sleep. Therefore, the blocking of this blue light wavelength could potentially establish a sense of physiologic darkness. Physiological darkness is an essential factor in a proper circadian rhythm. Using blue-light glasses as a blocking mechanism against the blue-light wavelength would positively impact sleep quality.
Blue light glasses are plastic eyeglasses that block blue light from reaching the eyes. These glasses have been proven to be effective at inducing sleep by reducing the activation of intrinsically photosensitive retinal ganglion cells (ipRGCs). ipRGCs are extremely sensitive to blue light and provide major input for circadian regulation that connect with the suprachiasmatic nucleus (SCN). The SCN generates the body’s circadian rhythm. When ipRGCs are activated, there is an increased amount of non-rapid eye movement sleep, increasing poor sleep quality and the disruption of the circadian rhythm.
The disruption of the circadian rhythm and the human sleep-wake cycle has major implications. In the article, the Circadian disruption and human health, by Dr. Phyllis C. Zee, the disruption in circadian rhythm and the human sleep-wake cycle is studied. It is found that these disruptions play a role in public health implications, and increase the risk of neurologic disorders, psychiatric disorders, metabolic disorders, cardiovascular disorders, and immunologic disorders. These disorders have been found to be increasingly higher in people with dysregulated circadian rhythms and sleep-wake cycles. Further research shows that there is a possibility of a treatment for these disorders, especially sleep and mood disorders. This treatment is the use of blue light in blue light therapy. This therapy consists of exposure as a regulator of the human circadian rhythm. When used correctly, consistently and during daytime hours, blue light therapy is an effective method to increase mood and sleep. However, it is still important that people make an active effort to manage their nighttime blue light exposure.
To manage blue light exposure, it is recommended that people wear blue-light blocking glasses throughout the day, to actively try to expose themselves to brighter light during the daytime to boost the ability to sleep and avoid looking at screens between two to three hours before falling asleep. The suggestion to avoid looking at a screen two to three hours before falling asleep comes from the fact that melatonin begins to secrete in the brain, raising its levels in human bodies about two hours before people begin to fall asleep. When this natural production of melatonin is disrupted, it is increasingly harder for someone to fall asleep and to stay asleep.
References
Hester L;Dang D;Barker CJ;Heath M;Mesiya S;Tienabeso T;Watson K; “Evening Wear of Blue-Blocking Glasses for Sleep and Mood Disorders: A Systematic Review.” Chronobiology International, U.S. National Library of Medicine, https://pubmed.ncbi.nlm.nih.gov/34030534/.
“Blue Light Has a Dark Side.” Harvard Health, 7 July 2020, https://www.health.harvard.edu/staying-healthy/blue-light-has-a-dark-side.
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