What is Blue Light? Why is It Significant?
Blue light is a specific wavelength of light that is emitted from computers, cell phones, televisions and other screens. Blue light is also naturally emitted outdoors, and why certain animals sleep when it is dark and others are active. It can also be a stimulator of seasonal changes in animals, such as growth of thicker coats in winter or a season-specific breeding season. These changes are all due to blue light’s connection to the production of melatonin, a hormone that induces tiredness among other things. This operates on a cycle, which without modern technology, would be dependent on the length of daylight and length of darkness perceived. Sight is a large contributor, but is not the only way to detect daylight changes, as studies by Charles Czeisler have shown the same receptivity to these changes in blind individuals as in seeing ones (Holzman 2010). In winter, many people notice that they are tired more often or earlier in the day than during the summer. This cycle is tied in with what is called a circadian rhythm.
The National Institute of General Medical Sciences defines circadian rhythms as “the physical, mental, and behavioral changes an organism experiences over a 24-hour cycle” which can be influenced by a number of factors including temperature, food intake, and light. Consider a person that consistently goes to bed at ten and wakes up at six in the morning. They likely will start getting tired around ten and begin to wake up at six more naturally, or at least feel less tired when they do so. During the winter months, this person finds themselves getting tired earlier and sleeping longer than they had before. If they randomly stayed up watching television until 1am and slept until 11am, they may feel “off” even though they got the same amount of sleep as usual. These are both examples of how light exposure may affect tiredness in relation to circadian rhythms.
Effects of Blue Light and Possible Solutions
Screens, as a large contributor to many people’s blue light intake in a day, have great potential to disrupt one’s circadian rhythm. A study by Dieter Kunz, the director of Research and Clinical Chronobiology Research Group at Charité-Universitätsmedizin Berlin showed a thirty minute delay in the onset of rapid eye movement sleep, also known as deep sleep, in subjects exposed to bright but not glaring light (Holzman 2010). However, many people cannot or do not want to avoid screen usage completely, so solutions such as blue-light protective lenses in glasses have been created. In a prospective clinical study by Ide et. al. these lenses were tested (Ide et. al. 2015). Thirty three participants were asked to complete a two-hour long, intensive computer task, with variable groups divided by lens blocking effect strength. The results were measured by tracking of critical flicker fusion (CFF). CFF is the ability to detect a flicker in a steady light source which is a good way to quantify temporal processing (Shinomori et. al. 2020). CFF ability naturally declines with age and excessive exposure to blue light has been shown to hasten the decline of CFF ability. This is concerning because that decline is also indicative of issues within the eye that may affect overall sight later in life. In the short term, it also tests visual fatigue. The results of the study from Ide et. al. showed that the increased lens protective strength showed a statistically significant improvement in the CFF of the subjects showing that the use of blue-light protection can yield positive results.
While protective measures may help while exposure is happening, it is believed by Kunz and many others that decreasing the amount of blue light before bedtime can help dilute the effects of long-term exposure, while still reaping the benefits of increased alertness and productivity that comes with blue light during the day (Holzman 2010). Thus, it may be helpful to put away screens at a specific and reasonable time before going to sleep to improve sleep quality habitually. It is important to pay attention to our circadian rhythms in our daily life, as more evidence is being collected showing the disorganization of circadian rhythms in correlation to diabetes, obesity, breast cancer, and other health-related issues (Holzman 2010). Luckily, there are many ways to improve circadian rhythm, from protection against blue light and maintaining a routine as mentioned before to meal times and environmental temperature. While it is not possible for everyone to control each of these factors every day, we all can benefit from doing our best to take care of our body and health where we can.
References
David C. Holzman (2010). Environmental Health Perspectives Volume 118, Issue 1. What is in a Color? The Unique Human Health Effects of Blue Light. https://ehp.niehs.nih.gov/doi/full/10.1289/ehp.118-a22.
National Institute of General Medical Sciences (2023). Circadian Rhythms. https://www.nigms.nih.gov/education/fact-sheets/Pages/circadian-rhythms.aspx.
Shinomori et. al. (2020). Textbook of Natural Medicine (Fifth Edition). Critical Flicker Fusion. https://www.sciencedirect.com/topics/medicine-and-dentistry/critical-flicker-fusion.
Ide et. al. (2015). Asia-Pacific Journal of Ophthalmology Volume 4, Issue 2. Effect of Blue Light-Reducing Eye Glasses on Critical Flicker Frequency. https://www.sciencedirect.com/science/article/pii/S2162098923005613. Assessed and Endorsed by the MedReport Medical Review Board