The effects of the blue light emitted by the screens of digital devices have long been discussed, especially when they are used late in the evening. There is a widespread belief that the glare from our smartphones, especially during the evening “scroll” before falling asleep, can prevent sleep or compromise the quality of rest. But to what extent is this idea really founded?
Recent studies suggest that the problem is more complex than one might imagine and that it is not enough to blame blue light alone. Let’s explore the question.
Blue light and circadian rhythm
The blue light emitted by digital devices, as well as by natural daylight, has short wavelengths that directly affect the receptors of the retina, which send signals to the brain influencing our circadian rhythm, the biological clock that regulates sleep and wake. This is the area on which many scientists have focused to understand whether the stimulus induced by screens can actually disturb sleep.
Stuart Peirson, neuroscientist at the University of Oxford, explains how the photosensitive cells in our retina, which capture blue light, transmit signals to the area of the brain responsible for regulating the circadian rhythm, and this also happens during the day, helping the organism to remain alert. While it is well established that prolonged exposure to blue light can delay the time you fall asleep, the actual impact it has when looking at a screen at night may not be as significant as commonly thought.
A question of intensity, not just color
A study conducted by Harvard University examined the effect of exposure to blue light from an e-reader on a group of participants. Even after four hours of reading under maximum screen intensity, there was only an approximately 10-minute delay in sleep onset compared to normal parameters. The results suggest that blue light, while having some responsibility, does not act in such a drastic way.
Peirson says that, in terms of brightness, natural daylight is a thousand times more intense than the light emitted by our electronic devices, and that even the artificial lighting of an average room far exceeds the brightness of a smartphone. So, what could really make the difference is not so much the type of light but its intensity and duration of exposureand reducing ambient lighting before bed may be more effective than simply avoiding blue light.
The effects of content on sleep
The impact of blue light therefore appears marginal, unless you expose yourself to bright screens for many hours, already having difficulty falling asleep. Various researches have highlighted that the type of content you consume while using your smartphone might be a more relevant factor. Emotionally engaging or stimulating content, such as social notifications or videos that arouse strong interest, could arouse a state of mental arousal that hinders the relaxation necessary to fall asleep.
Browsing social media or scrolling through feeds, in fact, can activate the production of dopamine, the hormone linked to gratification, which induces our brain to stay active to seek new stimulation. This condition is very different from the calm and progressive abandonment to the relaxation phase that precedes sleep, and it is therefore likely that it is precisely the mental activity linked to the content that prevents you from falling asleep easily, rather than the blue light of the screen itself.
What can you do for better sleep?
Given the complexity of the process that leads to sleep, experts recommend adopt some good practices which are more effective than using specific accessories such as glasses that block blue light:
Some of the major research conducted on the topic highlights the importance of adequate sleep hygienewhere the time spent in front of the screen represents only one of the many aspects to take into consideration. According to several studies, evening habits, the quality of the environment and nutrition play a significant role in regulating sleep rhythm, with even greater effects than exposure to blue light alone. It is therefore highlighted how blue light, compared to other wavelengths, can have specific effects on the production of melatonin, even if recent results are starting to show a more complex picture: light intensity and cognitive stimulation appear to have equally significant impacts on sleep compared to blue wavelengths alone.
To answer the initial question
While blue light may play a role in delaying falling asleep, it is a limited effect and closely linked to specific circumstances of prolonged exposure and high brightness. It is plausible that they are quite thereand habits and contents that are consumed while using the device to have a more marked effect on our ability to sleep peacefullytherefore, one more relaxing evening routinewhich can best prepare the body for night-time rest, to be combined with brightness adjustmentcould be more effective expedients than simply giving up screens.
