Sleep and Blue Light

byMBelle2

422 followers

4 months ago

Key points to remember:

• Exposure to blue light from screens in the evening disrupts our biological clock and reduces sleep quality.
  
• Exposure to blue light in the morning, on the other hand, stimulates wakefulness.

From bedtime to bedtime, from the youngest to the oldest, we're all hooked! We're talking, of course, about screens: smartphones, tablets, OLED TVs... More and more connected, but more and more tired. Everyone's talking about it, because it's now a real social issue: what's the link between screens and our sleep? Between our sleep and our health? Behind the scenes, a merciless battle is being waged: Blue Light Vs Melatonin.

If we mention the term “light spectrum”, you'll immediately think of your high school physics teacher explaining how light is broken down into a spectrum of colors. Have you ever seen a rainbow? Well, here's the most beautiful example of a spectrum of light broken down into its constituent colors.
There are 3 types of rays in the light spectrum, classified according to wavelength:

• Ultraviolet (UV): invisible, requiring sun creams and sunglasses,
  
• Visible: visible to the human eye,
  
• Infrared (IR): invisible, except to Predators.
  

The “blue light” we're interested in straddles 2 types of wavelength: UV and visible, and comes from 3 main sources:

• the sun,
  
• screens,
  
• LEDs.
  

Since it spans 2 wavelengths, there are two types of blue light:

• Blue-violet: located in the UV range, this is problematic for our eyes, as it is suspected of increasing the risk of developing Macular Degeneration (AMD) [1], and is found in particular in artificial HEV light (screens).
  
• Turquoise-blue: located in the visible spectrum, this is less harmful. It is even used in light therapy [2].

Or rather, like chickens. In fact, chickens have a rhythm that's as simple as getting up and going to bed with the sun. And after all, man is an animal (almost) like any other: have you ever wondered why we get up at the same time every day, without necessarily setting an alarm clock? It's the famous circadian rhythm, which lasts 24 hours and regulates our entire day. This cycle is observed in many species, and regulates :

• rising and setting,
  
• reproduction and parturition,
  
• body temperature,
  
• hibernation periods.
  

This biological clock is regulated by a small hormone known as melatonin. Its secretion at the end of the day helps us to fall asleep.

If melatonin production increases at the end of the day, it's because light intensity diminishes. Today, however, we no longer spend our evenings (and nights, depending on the series) in front of our screens. The blue light emitted by these devices stimulates receptors in our retina, which in turn signals the pineal gland (the melatonin-secreting organ) to reduce its production.
And there we have it. Exposure to screens causes a reduction in melatonin secretion, which disrupts our biological clock, delaying sleep and promoting insomnia. Ultimately, this whole mechanism reduces our sleep time and degrades its quality. And many physiological problems derive from these sleep disorders... [4,5,6]

Can't talk before your morning coffee? Would you like to be like in the ad but don't like chicory? Well, blue light isn't all bad! In fact, morning exposure to blue light promotes wakefulness and “re-synchronizes” our circadian clock by inhibiting the production of melatonin and increasing the production of cortisol (the wakefulness hormone).
This blue light also makes us feel more alert, and could even improve cognitive performance, particularly in students. [7,8,9,10].

If you don't want to count sheep to get to sleep, it's advisable to avoid screens for at least 1 hour before going to bed, so that your melatonin secretion can take place normally and promote sleep. You can also compensate for the lack of melatonin in the evening with a well-dosed nutraceutical.

Publications

1. https://www.inserm.fr/actualites-et-evenements/actualites/dmla-quelles-sont-ondes-lumineuses-responsables-perte-vision
2. Christine Blume, Corrado Garbazza, and Manuel Spitschan. Effects of light on human circadian rhythms, sleep and mood. Somnologie (Berl). 2019; 23(3): 147–156.doi: 10.1007/s11818-019-00215-x
3. http://www.bleuenlumiere.com/#bleuenlumiere
4. Leena Tähkämö, Timo Partonen, Anu-Katriina Pesonen. Systematic review of light exposure impact on human circadian rythm. Chronobiol Int. 2019 Feb;36(2):151-170. doi: 10.1080/07420528.2018.1527773.
5. B Claustrat , J Leston. Melatonin : Physiological Effects in Humans. Review Neurochirurgie. Apr-Jun 2015;61(2-3):77-84. doi: 10.1016/j.neuchi.2015.03.002
6. Yvan Touitou, Alain Reinberg, David Touitou. Association between light at night, melatonin secretion, sleep deprivation, and the internal clock : health impacts and mechanisms of circadian disruption. Review. Life Sci. 2017 Mar 15;173:94-106. doi: 10.1016/j.lfs.2017.02.008.
7. Kyungah Choi, Cheong Shin, Taesu Kim, Hyun Jung Chung , Hyeon-Jeong Suk. Awakening effects of blue-enrichef monrning light exposure on University Students Physiligical and subjective responses. Sci Rep. 2019 Jan 23;9(1):345. doi: 10.1038/s41598-018-36791-5.
8. William D.S.KillgoreJohn R.VanukBradley R.ShaneMareenWeberSahilBajaj. A randomized, double-blind, placebo-controlled trial of blue wavelength light exposure on sleep and recovery of brain structure, function, and cognition following mild traumatic brain injury. Neurobiology of Disease Volume 134, February 2020, 104679. doi : https://doi.org/10.1016/j.nbd.2019.104679
9. Anna Alkozei, Ryan Smith, Derek A. Pisner, John R. Vanuk, Sarah M. Berryhill, Andrew Fr and all. Exposure to Blue Light Increases Subsequent Functional Activation of the Prefrontal Cortex During Performance of a Working Memory Task.Sleep. 2016 Sep 1; 39(9): 1671–1680.doi: 10.5665/sleep.6090
10. Kyungah Choi, Cheong Shin, Taesu Kim, Hyun Jung Chung, Hyeon-Jeong Suk. Awakening Effects of Blue-Enriched Morning Light Exposure on University Students' Physiological and Subjective Responses. Sci Rep. 2019 Jan 23;9(1):345. doi: 10.1038/s41598-018-36791-5.

11. Gianluca Tosini, Ian Ferguson, Kazuo Tsubota. Effect of blue light on the circadian system and eye physiology. Mol Vis. 2016; 22: 61–72. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4734149/pdf/mv-v22-61.pdf