What is all this fuss about blue light? You’ve probably heard about it having something to do with the backlighting on your smartphone or other electronic device. But what actually is blue light? What’s it doing to your brain? Is it really that bad? In episode 20, Aleena and Janine are keen to see what the science says. They also have the final installment of the ever-popular segment: How’s Aleena’s Kitchen Renovation Going?!; Janine’s holiday nerdery; plus gushing over Björk’s new album AND podcast! OMG!
Mastering of this episode, plus intro and outro music, by the ever-talented Dr Adrian Diery.
First things first: here’s what you need to know abuot circadian rhythms and melatonin
A circadian rhythm is essentially a 24-hour body block and in humans. It controls things like sleeping and waking cycles, hormonal release, body temperature, eating and digestion – kinda important stuff! Exposure to light is linked with human circadian rhythms and the key regulatory hormone is melatonin. This so-called sleep hormone is produced by the pineal gland, and also in small amounts by the retina in the eye. Melatonin levels start to increase soon after the onset of darkness and reach peak levels between 2 and 4 am. Then levels gradually reduce until the time of waking. Infants produce very little melatonin (that makes sense!), and melatonin can be used as as sleep aid in many people. Exposure to artificial light at night can interfere with melatonin production, and therefore impact on circadian rhythms.
Blue light is part of what’s called the ‘visible spectrum’: the wavelengths of light that human eyes can detect. Blue light has a relatively short wavelength, compared to other colours of light. You can read more about light wavelengths here (and refer back to Episode 7 where Janine details her past research on satin bowerbirds and their obsession with the colour blue!). Importantly, there is nothing inherently bad about blue light: it is present in sunlight and we are exposed to it all day long! But blue light exposure at night, from artificial sources…? Let’s see what the science says…
Effects of night-time smartphone use with or without blue light
Heo and colleagues (2017) report that, in 2013, 39% of Americans surveyed were using smartphone within 1 hour of bedtime. The LED display of smartphones emits artificial light at night, including large amounts of blue light. Previous studies have shown that night-time exposure to blue light can suppress melatonin, interrupt circadian rhythms, increase fatigue, and hamper cognition and problem solving ability. On the other hand, exposure to blue light upon waking/in the morning has been shown to be helpful for alertness and even depression (see here and here).
Heo and colleagues’ study was the first to look into the effects of blue light from smartphones, rather than other light sources. Their study was very well designed (randomised + double-blind + crossover + placebo = awesome!). The placebo condition phones had LED displays that appeared ‘normal’ to the naked eye, but reflected no blue light at all (refer to Episode 8 regarding nocebo and placebo effects!). This study only included healthy males (refer to Episode 15 for a discussion around why excluding females from studies can be problematic!). Participants stayed at a medical research centre for 3 days and on the second night they played games on smartphones (either blue-light emitting or placebo) for 2.5 hours before bed.
When participants were exposed to blue light-emitting smartphones they were significantly less sleepy and less fatigued after smartphone use, and they performed significantly worse on cognitive performance tests, as compared to when participants were not exposed to blue light. When exposed to blue light, participants also had lower melatonin levels, a delayed onset for melatonin release, and higher body temperatures, but these differences were not found to be statistically significant. The authors describe the findings as clinically significant and suggest suppression of blue light at night.
Heo JY, Kim K, Fava M, Mischoulon D, Papakostas GI, Kim MJ, Kim DJ, Chang KJ, Oh Y, Yu BH, Jeon HJ. (2017). Effects of smartphone use with and without blue light at night in healthy adults: A randomized, double-blind, cross-over, placebo-controlled comparison. J Psychiatr Res., 87: 61-70.
Does blocking blue light at night reduce insomnia?
So are you wondering if there’s been any studies around night-time blue light exposure among people who already have a diagnosed sleep disorder? Janine was too! Aleena was happy to scratch that itch and tell us about this 2018 study by researchers in the USA.
In this randomised controlled trial, 14 men and women who had diagnosed insomnia wore amber blue light blocking lenses for two hours before bedtime (and during any night-time awakenings) for one week. Each participant also wore clear placebo lenses for a week: yep, this was another crossover design where participants do both experimental conditions and “act as their own control”.
When wearing the blue light blocking lenses, participants’ insomnia was significantly reduced. They also said that they slept longer and had better quality and soundness of sleep. Measures of sleep time from accelerometers (kind of like the fitness device you might wear on your wrist), also reported that participants slept longer. Sounds dreamy!
This was a small study and, since the researchers didn’t measure melatonin, we can’t be sure that insomnia was reduced because the blue light blocking lenses helped to normalise participants’ evening melatonin levels. Cue more research please. But this is a plausible explanation that fits with what we know about how blue lights effects circadian rhythms.
Meanwhile, did you know that in most (new) screen devices you can turn on the blue light filter in the settings? It’s often called “night light” or similar. Still, doing so won’t stop blue light from other sources in your home or external surroundings, such as house or street lights. So be mindful of these if you want to reduce blue light exposure at night. Hey, maybe consider wearing blue light blocking lenses for a couple hours before you hit the hay?! Aleena will! Janine also recommends free f.lux software to reduce blue light exposure from computers after sunset (if you have an older device without in-built blue light blocking settings).
Shechter A, Kim EW, St-Onge MP, Westwood AJ. (2018). Blocking nocturnal blue light for insomnia: A randomized controlled trial. J Psychiatr Res, 96: 196-202.
What brought out our inner square?
Janine has just returned from an awesome holiday to Western Australia. She nerded out constantly while on said holiday and was especially excited to see the one of the cutest marsupials – quokkas – on Rottnest Island!
Aleena is briefly interrupted by Janine who requested – apparently at the behest of various listeners – an update on her kitchen renovation dramas. It seems Aleena did not provide listeners with enough emotional closure on the issue. So here it is: the kitchen renovation is FINISHED. The drawers have covers AND handles. It is 100% complete. There is nothing left to do. The segment has concluded. Please stop bringing it up.
Meanwhile, Björk has a NEW ALBUM!!!!!!!!! Words can’t describe Aleena’s and Janine’s delight and general love of Björk, her new album, AND her NEW PODCAST. But they try to express it nonetheless (and things get a little off track…). But anyway, have you listened to Björk yet? If not, why are you even reading this? Go now and listen please and thank you.
A reminder to check out The Inner Square music playlist on Spotify – there might be the odd Björk track featured 😉
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