Blue light may not be as bad for sleep as suspected
- Richard J Yun
- Dec 29, 2019
- 2 min read
A few blogs back, I wrote about how blue light glasses may not be that useful. Another study shows that blue light may not be as bad for sleep as suspected.

For the last few years, general scientific consensus has suggested the blue light spectrum coming out of our modern devices can significantly disrupt our circadian rhythms. To balance this, many devices now come with night modes, offering yellow or sepia screen filters designed to cut out the most problematic blue spectrums of light. Now a new study from the University of Manchester is questioning that common consensus, arguing perceived color can also influence circadian clocks, and novel animal studies may reveal exposure to yellow light at night could be confusing our body clocks.
Alongside the rods and cones in our eyes we have a small amount of innately photosensitive cells. These cells are designed to not help us see, but rather sense light as part of our circadian management system. When these specific retinal cells sense light, they produce a molecule called melanopsin, which directly tells certain parts of our brain to stay awake and alert. As well as suppressing melatonin, melanopsin has been found to help regulate and set our body's circadian rhythm.
This is a blue spectrum of light, and it tends to be the most prominent spectrum displayed by the LED screens used in many of our modern digital devices, from smartphones to laptops.
The research seems implicitly critical of those digital device “night modes” which add a warm yellow hue to screens in the evening. But it is important to note that this new study was only conducted on mice, and although the researchers are confident there is evidence to suggest the effect detected could extend to humans, there is no evidence that the perceived color of light is significantly influential on human circadian systems. In fact, some research has been conducted revealing interventions such as wearing amber-tinted glasses for an hour or two before going to bed may enhance the quality of a person’s sleep.
While it may be clear blue wavelengths of light activate circadian-regulating mechanisms in the human brain, it is not clear yet whether a yellow-filter on a device’s screen markedly influences the human circadian system. So you don’t necessarily need to go and switch off that night mode on your laptop just yet.
Personally, I have noticed a difference when I put on blue-light glasses or turn on night mode. Maybe it's a placebo effect, but whenever I switch it off or don't use blue-light glasses, I always feel that my eyes are drying up and uncomfortable when staring at my laptop or phone for a long time.
I'm a UofT student and this is a student exploration project sponsored by KiImpact.com
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