Light… The giver of life.
Yes, absolutely mostly true. Especially if the sun / God / plants are involved. As with most things however, humans tend to screw it up…
Light affects physiology and behaviour in humans both indirectly through clock synchronization and circadian rhythms, and directly through the promotion of alertness, with the help of tricky things like retinal ganglion cells, our retinohypothalamic tract, and this bloated sac of protoplasm we house in our skulls. In terms of the type of light that is the most powerful, because there can be only one, it would probably have to be blue light (450-490 nm).
Nerdy scientists (yes, I am slightly jealous) have of course shown the basis of all this shizzle in the animal kingdom, where cryptochromes (blue/UV-A-absorbing photoreceptor proteins discovered originally in plants) are present to entrain our circadian rhythms. Just fascinating.
Evidence that exposure to blue lights affects sleep
A single 30-minute exposure to blue light is already enough to boost brain working performance and executive function, improving alertness and decision-making. Not so great at 11pm.
Reading an iPad for just 30 mins before sleep decreases subjective sleepiness and delays onset of deep sleep, compared with reading a book.
Blue-light exposure results in less deep sleep (necessary for memory consolidation, and lots of other important things like ‘resting’ the brain), particular in the frontal areas (needed for decision-making, planning, etc).
Time matters: just 30 minutes of device use increases alertness at bedtime… Two hours of use affects melatonin levels. In fact, the effect of blue-light on melatonin suppression is dose-dependent; a tiny amount of blue light has a greater suppressive effect on melatonin than the white fluorescent light currently used in most general lighting fixtures.
Blue light doesn’t only affect sleep…
It can also:
- Induce photoreceptor damage
- Increase the risk of cancer (eg. breast, prostate)
- Make you fat (clutches face in horror): well, possibly fatter. People exposed to blue light in the evenings (low enough intensity NOT to affect sleep) have suppressed energy metabolism the next day.
(Quite scarily) artificial light-induced changes to the circadian rhythm signal are communicated maternally at the very onset of life and after birth via breast or artificial formula feedings. The deleterious effects of blue-light exposure are worsened by a lack of natural light exposure (due to work environments, fear of sun exposure due to skin cancer risk and ageing, etc). So in the present day (avoidance of sunlight PLUS increased device use), it’s a double whammy. For bad things.
Which devices are better / worse for blue light emissions?
One group of researchers compared the blue light emissions from:
- A tablet (iPad)
- An e-reader (Kindle Paperwhite 1st generation)
- A smartphone (iPhone)
They found that all of these devices shared the same blue light emissions. (I was totally surprised to read this – FULLY expected the Kindle to be less ‘blue light’ damaging…)
What can you do to combat the disruptive effects of blue light on sleep?
Have exposure to bright light during the day / Use blue light exposure only at certain times.
One study had subjects exposed to bright light during the day, then during the evening they either read a book under dim light, or read a tablet. Nil differences were found between the two groups in terms of sleep parameters or melatonin levels – suggesting that exposure to bright light during the day may help combat sleep disturbances associated with the evening use of electronic devices emitting blue light.
Another study found that blue light exposure in the daytime helps prevent a messed up circadian rhythm in those who have light-induced melatonin suppression – eg. Hospital and shopping centre workers.
Use blue-light blocking glasses / filters.
In patients with Delayed Sleep Phase Disorder (essentially they go to bed later and wake up later than what is considered normal AND this sleep pattern interferes with ‘regular daily life’), the wearing of blue light-blocking amber glasses every evening for two weeks helped with getting them to sleep earlier.
Actually, DSPD is commonest in adolescents (some argue that for them it is natural, not a disorder). Adolescents today have the combined effect of their biology (which makes them go to sleep, and wake up, later) and their behaviour (screen time). A study gave a bunch of teenage boys ultra trendy blue-light blocking glasses (ok, so there was no actual mention of how cool they were) and found that they improved nighttime melatonin secretion, reduced bedtime attention vigilance and alertness.
“So sweetie, don’t drink, don’t have sex, don’t use drugs, and make sure you wear your DANG BLUE-LIGHT BLOCKING GLASSES”. Yeah sorry, I just don’t see it happening.
Even in normal people (eg. Those without DSPD, non-adolescents), wearing a blue-light shield for two hours in the evening when using devices results in higher overnight melatonin secretion, quicker time to sleep, improved sleep quality, all without interfering with visual quality, when compared with control eyewear without blue-light filters.
These blue-light blocking lenses are amber – don’t make the mistake of getting the yellow-tinted lenses (these block UV light only, no good la).
Blue-light blocking lenses don’t only improve sleep, they also improve mood (er, most likely because you have slept)… Holy crap I wonder if wearing amber lenses will improve the poor mood associated with non-blue-light-associated-chronic-sleep-deprivation-due-to-young-children (aka NBLACSDDTYC Syndrome)?
Hey, while we’re on the topic of mothers, studies have shown that wearing blue-light blocking glasses can potentially reduce post-partum depression. Just like succeeding in looking for postpartum belly wrap – major win right?
The argument is that the new mother has to get up in the middle of the night (when melatonin is usually high), and light exposure messes with her sleep, thereby causing depression. Authors daringly state that “new mothers will benefit from using glasses and light bulbs that block blue light when getting up at night to care for their babies”. There is no mention however as to the strength of this recommendation in reducing postpartum depression when compared with, you know, other tiny factors like – a history of depression or postpartum depression, other stressors (psychosocial), an asshole partner who is unsupportive… Also I don’t feel the authors have thought out the practicalities of their suggestion – I’m feeling now is a good time for a ROLE PLAY!
You are a depressed new mother. You feel like you cannot cope with everything/ anything and your world is collapsing in around you. Luckily for you, nice (but with no contact with real life) researchers have provided you with a nice pair of glasses that block blue-light. You must wear them when you get up during the night. You must not turn on the light without first wearing them. You are grateful that soon all your sleep and mood problems will be solved.
Cue: baby cries.
“Where are those glasses?”
“I can’t find them if I can’t put on the light.”
“I can’t put on the light until I find them.”
“Sigh, the baby won’t stop crying.”
“I’m a shit mother. I can’t even wear a pair of glasses, let alone look after a baby.”
“I’d better deal with the baby first…
“What’s that on the change table? Oh THERE are those glasses, yay I found them.”
Yep. That’s how it will go. Bless the authors for trying though. Actually as I read the reference again, I realise that their paper is published in “Med Hypotheses”…
You gotta pick your subjects sometimes and rather bizarrely someone carried out a study with blue-light emitting goggles in college students. They put some blue-light goggles on freshman varsity cheerleaders and members of the delta-iota-chi-kappa fraternity* and found that blue-light negatively affects their sleep. There was however no mention of the possible effects of confounding factors such as alcohol, drugs, parties, and general horsing around. Yeah, because in college students, mostly definitely blue-light is their main cause of their lack of sleep.
(* names changed to protect the true identities of subjects)
You can… Just… Wait…
Blue-light doesn’t affect oldies as much (for the sake of argument, ‘old’ was defined in this study as over 60 years). The blue light just doesn’t stimulate the brain areas for alertness and higher executive function as much.
Why? Another study suggested it was due to the ‘normal’ age-related yellowing of the lens in the eye, acting as a ‘natural’ blue-light filter. Mother nature is clever. Or maybe not, because that means (study proven) that oldies are also not getting as much of the brain-enhancing effects of light stimulation – the yellowing lens also prevents the regular daytime light coming through to receptors, making sleep quality poorer.
Look for ‘sleep aware’ apps / Devices with ‘bedtime’ mode
Some app designers are beginning to make ‘sleep-aware’ programmes, where blue-light emissions are deliberately reduced, and apparently all hardware should/ could have ‘bedtime mode’ that shifts blue and green light emissions to yellow and red as well as reducing backlight/ light intensity.
Does anyone know if this exists yet? Please comment below if you know!
Bottom line: blue-light from light-emitting electronic devices messes with your sleep in a dose-dependent manner. Fight the effects with judicious device use and appropriate blue-light blocking eyewear / filter, or just wait until you’re old. Don’t mess with new mothers. Ever.
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