You’ve probably heard that blue light is bad for you and disrupts sleep. But, like most things, the reality is a bit more complicated. The idea that blue light before bed, from devices like smartphones, is solely responsible for keeping you awake isn’t entirely accurate (1).
In the past, the sun was the primary source of blue light. Light from the sun had a wake-promoting, alerting effect during the daytime. Overnight, with no external light sources, we lived in near-complete darkness.
With the widespread use of digital devices such as laptops, TVs, and smartphones, artificial light exposure has become a constant part of daily life, both during the day and overnight. As a result, the potential adverse effects of blue light on sleep and overall health have come under growing scrutiny.
Does artificial screen light before bed ruin your sleep? The jury’s out on this. Some studies suggest it might delay sleep, by less than 10 minutes on average (1). Melatonin, the hormone produced in high levels overnight, is considered the ‘biological marker of the night’ and a good marker of our circadian rhythms (4). Studies looking at melatonin levels after bright light are also mixed. (2, 5). Why the confusion? Natural outdoor light from the sun is significantly (over 300x) brighter (6) than any normal indoor artificial light and has a much bigger impact on our circadian rhythms. In the grand scheme of things, screen light might not be the sleep disruptor it’s made out to be.
How important is natural light?
Interestingly, some researchers have shown that natural daylight exposure can help mitigate the effects of artificial light at night (2). By maximising natural light exposure in the daytime, the potential minor impacts of artificial light around bedtime may be mitigated. To optimize our sleep, we should focus on getting as much natural daylight exposure as possible, particularly first thing in the morning, rather than worrying too much about the use of screens around bedtime.
Is blue light before bed really the problem?
While blue light before bed may have some effects, the bigger issue is screen time displacing sleep (1). If you spend an extra hour scrolling on your phone but still wake up at the same time, you’re simply getting less sleep overall.
That’s not to say light doesn’t matter – our circadian rhythm is strongly influenced by natural light. Morning light exposure helps regulate the sleep-wake cycle, while dim lighting in the evening signals the body to wind down. The light from phone screens is relatively dim compared to daylight or even indoor lighting, so it’s important to look at how you’re using your smartphone before bed and whether it’s eating into your sleep time.
Do blue-light-blocking glasses work?
Blue-light-blocking glasses have gained popularity but the jury is out on their effectiveness. Limited research has examined their efficacy, and results have been inconsistent — some studies report benefits, while others find no significant effect (3). Instead of investing in specialised glasses, a more practical approach is simply reducing screen time before bed and lowering screen brightness in the evening.
While blue light has been widely blamed for sleep disruptions, research suggests that the real issue is more complex. Rather than focusing solely on blue light, a better strategy for improving sleep is managing screen time, getting sufficient morning light exposure, and making sure you’re getting the amount of sleep you need to feel your best.
References
1. Bauducco S, Pillion M, Bartel K, Reynolds C, Kahn M, Gradisar M. A bidirectional model of sleep and technology use: A theoretical review of How much, for whom, and which mechanisms. Sleep Med Rev. 2024 Aug;76(101933):101933.
2. Rångtell FH, Ekstrand E, Rapp L, Lagermalm A, Liethof L, Búcaro MO, et al. Two hours of evening reading on a self-luminous tablet vs. reading a physical book does not alter sleep after daytime bright light exposure. Sleep Med. 2016 Jul;23:111–8.
3. Shechter A, Quispe KA, Mizhquiri Barbecho JS, Slater C, Falzon L. Interventions to reduce short-wavelength (“blue”) light exposure at night and their effects on sleep: A systematic review and meta-analysis. Sleep Adv. 2020 Jun 4;1(1):zpaa002.
