Blue light: what are the health risks?
The French are increasingly exposed to artificial light. According to a study conducted in 2019, 55% of French people spend between 2 and 4 hours a day in front of a screen, 21% from 5 to 7 hours and 16% 8 hours or more (1) . Among the various risks (sedentary lifestyle, risk of obesity , disruption of sleep and social interactions), the increased exposure to blue light is of concern. What is it and what are these dangers?
What is blue light?
Blue light is actually part of the light spectrum – that whose wavelengths range from 380 to 450 nanometers. This light is called “blue” because its wavelengths, which are shorter than those of the illuminant (light source), are perceived as bluish.
Blue light is visible to the human eye . It also represents about a third of the light that we are able to perceive. It exists naturally, through the rays of the sun or lightning. But there are also artificial sources of blue light: domestic lighting, screens, lamps dedicated to phototherapy (or light therapy) or any other device operating with LEDs. “Cold white” light source devices are particularly blue light sources.
Finally, we often speak of blue light to actually describe blue-violet light, with wavelengths between 380 and 450 nanometers. But there is a second blue light: blue-turquoise light, whose wavelengths are between about 450 and 500 nanometers. These two lights produce different effects on the body when exposed to excess. However , our lifestyles (prolonged exposure to screens, modification of lighting modes to save energy) have drastically changed our exposure to blue light . The repercussions are also beginning to be clearly observed by the medical profession.
How is blue light dangerous?
Blue light itself is not dangerous. Frequent and prolonged exposure to blue light is what makes it dangerous . Gold :
- The replacement of incandescent lighting sources by other light sources (light-emitting diode or LED, “cold white” light), as well as the increase in light pollution (2.2% increase between 2012 and 2016, worldwide (2) ) increased this exposure.
- Our increasing use of screens – television, computer, smartphones and tablets, both in our professional activity and our leisure activities, has also contributed to increasing our exposure.
Thus, today we are more subject to the harmful effects of blue light. We list mainly two of them.
The impact on ophthalmic health
Blue light is, in itself, important for our vision skills. It performs important functions in our ability to perceive colors. It also contributes to the reflex contraction of the pupil. But repeated and/or prolonged exposure to blue light can:
- Cause inflammation of the cornea (3) and thus generate a dry eye phenomenon (4)
- Damage the retina, causing degeneration and modification of its morphology (5)
- Cause damage to the retinal barrier (blood impermeability) (6) or even necrosis or apoptosis of retinal cells (7)
- Cause age-related macular degeneration, by accelerating the aging of the retina (oxidative stress) (8)
The impact on the circadian rhythm
The circadian rhythm is in fact the “natural” biological rhythm, over a period of approximately 24 hours. It is in fact the sleep-wake rhythm, which manages the daily life of many species, such as humans. Blue light, naturally present in daylight , participates in the regulation of the circadian rhythm, captured by the ganglion cells of the retina. Thus, naturally, our perception of light via our eyes makes it possible to naturally “trigger” waking states (exposure to daylight) and sleep states (decline in the level of perceived blue light).
However, overexposure to blue light at night, via screens and/or artificial lighting, disrupts the circadian clock, with significant health consequences (9) :
- brain over-stimulation
- An increase in the secretion of cortisol (nicknamed “ stress hormone ”)
- A reduction in the production of melatonin (nicknamed “sleep hormone”)
- A noticeable deterioration in the quality of sleep and, more generally, sleep-wake cycles
The most vulnerable people
All individuals need to be careful about their exposure to blue light. Nevertheless, some audiences are particularly fragile:
- Babies, children and teenagers, because their ophthalmological development is in progress (for example, clearer lens).
- Pregnant women whose biological rhythm, already disturbed, risks suffering even more from excessive exposure to blue light.
- People suffering from ocular pathologies or anomalies: vision disorders, malformation, elderly people (cataract, AMD).
- Migraineurs, sensitive to light.
- Professionals, especially those exposed all day to LED lighting, as well as night workers, whose circadian rhythm is already altered.
What solutions to protect against the effects of blue light?
Health authorities, like ANSES, regularly update their recommendations for use by the general public in terms of exposure to blue light. Thus, the first protection remains information (10) , since a regularly informed public will be better able to make good decisions for their health.
That being said, the solutions to protect against the effects of blue light are relatively well known.
They consist first of all in limiting your exposure to blue light, at home, especially in the evening. To do this, it is recommended to:
- Use low temperature domestic lighting (“warm white” rather than “cold white”), below 3000 K.
- Give preference to indirect lighting sources and equip yourself with lamps with lampshades (dim light).
- Buy domestic equipment that meets blue light standards.
- Avoid as much as possible the use of screens in the evening and even more so at night.
In addition, wearing “filtering” glasses can significantly help. They do not dispense with blue light avoidance measures, as they only manage to filter about 20% of blue radiation. Also, they do not constitute an infallible protection against the harmful effects of blue light.
Finally, it may be possible to adjust your screen(s), using a less blue (“warm”) setting or using the “blue light” filter (available on most current phones and tablets). This setting is particularly recommended in the evening, as soon as darkness sets in. But, as for glasses, it is a relative palliative, and does not dispense with avoidance measures.
Stephen Paul is the lead author and founder of My Health Sponsor. Holder of a diploma in health and well-being coaching with more than 200 articles in the field of health, he makes it a point of honor to offer advice based on reliable information, based on scientific research, and verified by health professionals.