Blue light from screens and sleep

Blue light from screens and sleep: what are the dangers?

The harmful effect of new technologies on sleep is no longer a secret. 

In addition to disrupting the circadian rhythm, essential for the regeneration of the body and its cells, exposure to screens can perpetuate serious sleep disorders in the long term.

Quality sleep is essential at any age to stay physically, mentally and emotionally fit.

In general, it is strongly recommended that you avoid exposure to screens for at least 2 hours before going to bed. 

According to Public health expertise and reference centre of Québec (INSPQ), it would be preferable to avoid any cognitive stimulation, such as doing homework or playing video games, at least one hour before going to bed. 

However, the main cause of these disorders is not only the screens themselves, but also the blue light they emit. 

What is blue light?

Blue light from screens

What is called blue light is a part of the light spectrum, whose short wavelengths are between 380 and 500 nanometers. This light is emitted by the sun, but also by other artificial light sources, such as LED bulbs and more commonly screens (tablets, televisions, computers, smartphones).

Many studies have shown that exposure to blue light is the cause of many harmful effects on human metabolism: eye irritation, cataracts, photochemical lesions of the retina and lens, macular degeneration, headaches, and of course ... sleep disorders! 

To protect oneself, there are anti blue light glasses, designed to filter it and to reach the retina only in tiny quantities. 

We offer a wide range of anti blue light glasses on our website

How does blue light from screens affect our sleep?

blue from screens and sleep

The effects of blue light emitted by the screens modifies the circadian rhythm by suppressing the secretion of melatonin (the sleep hormone), and thus deteriorates the quality of sleep.

But what is the circadian rhythm?

It is a rhythm (or rather a cycle) that is defined by the alternation between wakefulness, i.e. the period of the day during which we are awake and sleep, i.e. the period during which we are asleep. 

The circadian rhythm lasts about 24 hours and can vary from one individual to another.

This variation is limited to one or two hours. 

Generally speaking, light, whether natural or artificial, plays a determining role in the biological clock and synchronizes the vital functions of the human body.

For example, body temperature, blood pressure, alertness and cognitive performance are at their highest during the day because they are stimulated by different types of light.

However, according to Dr. Claude Gronfier, even small light flashes of a few milliseconds at night can delay the biological clock, and the system is so sensitive that light acts even if we are asleep with our eyes closed. Indeed, even at low light intensity, the circadian rhythm is impacted.

Blue light is even more harmful because it stimulates and then activates the retina's receptors due to its luminous intensity, sending a message to the brain that it is still daylight.

For example, the simple fact of reading a message in bed sends a strong signal to the metabolism, which can disrupt the secretion of melatonin. 

As a result, the time it takes to fall asleep is delayed, and multiple awakenings can occur. 

 What are the tips for quality sleep?

quality sleep

The first measure to take in order to keep a normal sleep cycle is obviously to get away from screens before going to bed. 

It is recommended to avoid being exposed to blue light from screens at least 2 hours before going to bed, for an optimal sleep time. 

You can simply put your electronic devices away from your bedroom. This is also an opportunity to put an end to your bad screen habits. 

Instead, reading a book will help you sleep more efficiently. Reading a book will not cause a drop in melatonin secretion. On the contrary: reading will help your eyes to calm down and will even help you to improve your memory! 

Of course, we are talking about a physical book here, and not reading on a computer or cell phone, which would not improve your sleep.  

If you have to use some type of screen in the evening, make sure to respect a distance of at least 60 centimeters between your eyes and the screen in question. You can also activate a night mode, that will reduce fluorescent lights and bright light from your screen. 

If the distance is even a little bit shorter, your eyes will be irritated for a long time! 

An optometry study (the discipline of making measurements on the eye) from the University of Houston showed how melatonin production decreases drastically when exposed to blue light, and how simply wearing blue light glasses increased melatonin levels in screen users by about 58%.  


It is clear that appropriate screen time is therefore conducive to quality sleep, at any age and especially in children and adolescents in whom sleep represents an essential growth phase. Lack of sleep can also have bad repercussions on the human body in the long term. 

Blue light, which causes a decrease in melatonin in the human body, should therefore be avoided a few hours before bedtime, and especially blue light at night.

Light, and principally led lights, can affect the circadian clock as well as the energy efficient.

Moreover, the use of blue light blocking glasses will allow you to fall asleep faster, if you have to use screens in the evening.