What is blue light?

Blue light is a type of high-energy visible light, with a wavelength between 400 and 450 nanometers. It is emitted by many sources of light, from the Sun to LED screens. Scientists have issued warnings about the dangerous nature of blue light. All the same, it’s not certain that the “night mode” on our devices is any better for our eyes.

In recent decades, the general public’s exposure to blue light has massively increased. This is due to LED screens being much more present in society, in artificial lights, as well as smartphone, tablet and computer screens.

According to scientists, blue light can be dangerous. It can lead to impaired version, and is allegedly a risk factor for cataracts and age-related macular degeneration. Furthermore, being exposed to blue light in the evening or at night can disturb our circadian rhythm. Past studies have suggested that it suppresses melatonin, a hormone which affects sleep. To sum up, the more we are exposed to blue light, the more our sleep quality is affected. 

Since the risks associated with blue light were discovered, smartphone and PC manufacturers have developed “night modes” for their devices. When activated, displays automatically shift to an orange-yellow tint from a certain time in the evening through to sunrise.

But a study published in December 2019 showed that night mode may not actually be better than blue light, and could even be worse. Researchers at the University of Manchester carried out experiments on mice. They found that blue light was less disruptive to their sleep, compared to yellow light of the same brightness.

This may be because “cold” colours, such as blue, are closer to the colour of natural nighttime light. Whereas on the other hand, it’s more natural to look at warmer colours during the day. Our body clocks rely on shades of light to determine whether it’s time to sleep or be awake. Blue light may therefore disturb sleep less than night mode, which uses daytime colours. 

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