The fight against blue light
Over the last few years there has been growing interest from the public on the effects of blue light exposure on sleep duration and quality, especially with the abundance of blue light from digital displays like your phone or computer. There are various products on the market designed to reduce blue light exposure, all of which claiming they will give you a better night’s sleep. This includes filter settings for digital displays, blue light-blocking glasses and contact lenses, and even supplements that supposedly protect your eyes from the effects of blue light from the inside.
Why does blue light supposedly impact sleep?
The theory behind this anti-blue light trend is fairly reasonable. There are certain cells in the eye that contain a light-sensitive pigment called melanopsin. Rather than being directly involved in visual processing, these light-sensitive cells essentially tell the brain if your surroundings are bright or dark (i.e., whether it is day or night). When exposed to light, these cells inhibit the release of the sleep hormone melatonin. This helps align the body’s circadian clock with the Earth’s day-night cycle. Importantly, these cells are particularly sensitive to the blue part of the light spectrum, and it is this sensitivity to blue light that has been the driving force behind the recent movement against blue light.
Blue light might not be the true culprit
Despite this solid-sounding theory, there are still questions around whether everyday exposure to blue light is directly linked to poor sleep quality. Studies investigating the impact of blue light exposure on sleep duration have shown mixed results. A review published in 2022 found that only 3 out of 9 studies reported reductions in sleep duration following exposure to blue light, with one study even reporting an increase in sleep duration. Furthermore, the efficacy of techniques that reduce blue light exposure to supposedly improve sleep are similarly inconclusive. A review of blue light-blocking glasses published in 2023 analysed 17 different trials and found no conclusive evidence that these lenses significantly improved sleep duration.
Dr Russell Foster, a sleep scientist from Oxford University, argues that when it comes to the effects of light exposure on sleep, brightness may be a more important factor than colour. He notes that regardless of the source, bright light is known to increase alertness and can alter your body clock. Further, the light emitted from most phone and computer screens may not be bright enough to trigger a significant response from those melanopsin-containing eye cells that regulate melatonin production. Ultimately, the take-home message seems to be that we should do our best to reduce exposure to bright light before bed, regardless of whether it is blue light from our phone screens or white light from the lightbulbs in our homes.
References
Silvani, M. I., Werder, R., & Perret, C. (2022). The influence of blue light on sleep, performance and wellbeing in young adults: A systematic review. Frontiers in physiology, 13, 943108. https://doi.org/10.3389/fphys.2022.943108
Singh, S., Keller, P. R., Busija, L., McMillan, P., Makrai, E., Lawrenson, J. G., Hull, C. C., & Downie, L. E. (2023). Blue-light filtering spectacle lenses for visual performance, sleep, and macular health in adults. The Cochrane database of systematic reviews, 8(8), CD013244. https://doi.org/10.1002/14651858.CD013244.pub2
Foster, R. G., Hughes, S., & Peirson, S. N. (2020). Circadian Photoentrainment in Mice and Humans. Biology, 9(7), 180. https://doi.org/10.3390/biology9070180
