It is not the blue light that is responsible for our insomnia.
We are continually bombarded with messages warning us that we are using screens too much, to the detriment of our vision. Hence the flood of ads that encourage us to use filters to block the blue light from the screens before it’s too late…
“It will improve your rest”, “It will reduce eye strain caused by electronic devices”, “It will prevent eye disease”.... These are some of the many promises made.
How true is that? What damage do digital screens actually do? And above all, is it true that we damage our sight and our rest with the blue light they emit?
Understanding Blue Light
Artificial lighting cannot be accused of all evils. It has even been a blessing for our species, as it has allowed us to lengthen our days. Recently, however, much of this “extra time” has been spent on electronic device screens, which are known to have a large blue light component, cooler than conventional tungsten or fluorescent light bulbs.
Specifically, blue light is the spectrum range of visible light with a wavelength between 400 and 495 nanometers. It is a type of high energy light like violet and indigo. This type of light is naturally produced by the Sun, which also contains other forms of visible light invisible to the human eye, such as ultraviolet and infrared rays.
Is there a physiological consequence to the fact that the light to which we are most frequently exposed, day or night, is «very» blue?
Let us return for a moment to the effects of the Sun’s light. It is already one of the factors that help regulate our central biological clock, the circadian cycle. When light reaches our retina, it interacts with the photoreceptors present (cone cells and rods, allowing color and night vision) and other photosensitive cells – such as certain lymph node cells containing melanopsin, that regulate this circadian cycle.
Blue light prevents the latter from secreting melatonin, the so-called sleep hormone, because it promotes sleep (although it is not excluded that all the light reaching the retina has an influence). It follows that if we expose ourselves to blue light as we prepare to sleep, we block the secretion of melatonin which leads to dysregulation of the sleep cycle.
Things seem clear… Except that most studies in this area are not representative of our average exposure to blue light. Indeed, most experimental conditions do not correspond to the daily life of an average person. And even in this case, changes in the quality of sleep remain quite minimal (differences of ten minutes in falling asleep). In addition, these are usually studies with a small number of participants: less than twenty most often, and almost always young men. As a result, the harmful impact of blue light no longer appears so great.
But if there were a problem, are the much vaunted filters a solution? In fact, recent research indicates that blocking blue light by filters does not guarantee a better quality of sleep. Of course, it is easy to look for a single culprit, the blue light, to contrast it with a simple remedy, a filter, and to convince ourselves that we are doing what is best for our sleep… while continuing to use our electronic devices!
It’s not so much the excess blue light, which studies show is not powerful enough to seriously disrupt our circadian cycle, but what we do with our screens that keeps us from falling asleep. The real solution is to turn off our phones and other screens and fall asleep.
If you look at the claims about the usefulness of these filters, many manufacturers are saying that their products are needed for everything we do on a day-to-day basis. To do this, they point out that blue light damages our retina and contributes to the development of age-related macular degeneration, and that we must therefore avoid it permanently.
It should be noted that most of the work linking blue light to lesions in the retina (or brain neurons) has been done either on cultured cells or on laboratory animals such as fruit flies. These experimental conditions and models do not resemble the characteristics and protection of human eyes.
Blocking blue light by various filters does not prevent or delay visual pathologies.
In addition, the light intensity or exposure time used in these devices is very different and higher than in our electronic devices. Caution should therefore be exercised when extrapolating these results to human physiology.
However, studies have shown that blocking blue light by various filters does not prevent or delay the development of these pathologies.
Filters can be counterproductive
Many companies continue to warn against exposure to the slightest blue light from our screens and stir up fear of harmful effects to sell their filters.
This is not only useless if one has a reasoned use, but also counterproductive: during the day, we need to perceive the light, including blue, to regulate our circadian cycle. To such an extent that in an attempt to mitigate a disruption of this cycle due to a lack of daylight, what is the best treatment? Not a filter, but exposure to light.
When we use too many filters, the information our brain receives is confusing. On the one hand, external stimuli tell our biological clock that we still need to be awake… But on the other hand, by completely removing information about blue light, the cycle of melatonin is activated as if we were asleep. And it can really disrupt our circadian rhythm. In addition, removing information about blue light without needing it impoverishes our vision.
Conclusion: If you are worried about the quality of your sleep, the best thing to do is to put your mobile phone, tablet or computer aside for a while before you fall asleep. Blue light is not responsible for our insomnia…