A Time article [0] reports on this paper [1] that reaches the same conclusion as the user's comment. However, it's a mice study, which is an important limitation because rodents are nocturnal, according to the Time reporter.
Meanwhile, Harvard Health [2] and WebMD [3] also both continue to report that blue light suppresses melatonin production for humans.
From Time: "Animal studies should always be taken with a grain of salt, as they often do not translate directly to human behavior. And there are additional caveats to this particular paper, says Dr. Cathy Goldstein, a sleep specialist at Michigan Medicine. The researchers looked specifically at cones in the animals’ eyes, which detect color, instead of melanopsin, which senses light and is central to the issue of melatonin secretion.
"They also kept light levels dim, regardless of color, which may not reflect the bright lights of electronics.
"And finally, though mice are frequently used in sleep research, Goldstein notes that since the rodents are nocturnal, they may respond differently to light than humans do. Taken together, Goldstein says these conditions mean the study’s results apply only to a very narrow set of circumstances and metrics. “For this to get extrapolated to saying ‘blue light at night isn’t bad for you’ is a little bit of an extension,” Goldstein says."
Michael from f.lux: This research is from a very talented group of researchers, but it is unclear if it will translate from nocturnal mice to humans (as others have said). The evidence in humans is mixed, but it either shows no effect or a tendency in the other direction. There is a study in the same issue (Spitschan) that says there is no effect in humans.
1. First, the study does not question the contribution of melanopsin (the blue-cyan opsin that got everyone talking about "blue light") - it asks a more subtle question: when you hold melanopsin stimulation constant, what does the remaining light do and why? Here they are finding whether the cones oppose or boost melanopsin based on color signals. But regardless of how this works in humans, we should still expect bright-enough blue light at night to be stimulating, because of the response due to melanopsin.
2. Holding the melanopic portion of a light constant is not something we usually do. For most lights we have today, the "blue" lights would be considerably dimmer than the "yellow/red" ones if we did this. When we compare lights of equal visible brightness, the yellow ones are known to have less effect on human melatonin suppression [Chellappa 2011].
3. The evidence in humans is mixed, but it actually goes the other direction (saying blue is more stimulating), or there is no clear effect. In the same issue, a study on humans by Spitschan found a negative result on whether or not S-cone contrast has an effect: https://www.cell.com/current-biology/fulltext/S0960-9822(19)...
3b. Other research (in monochromatic and polychromatic light) finds that humans are more sensitive to blue light than melanopsin would suggest. See a list below.
4. We're all still trying to explain how the transition to dusk is blue/purple, while our own lighting doesn't do that. We have built our lighting to be relatively bright, but warm. It is not "natural" to extend the day like we do, but it likely would not help anything to make the lights more blue, unless they were quite a lot dimmer, or used very novel spectra.
Here is a list of references for the evidence +/- blue sensitivity (not melanopsin) in humans:
2. The Spitschan study from this same issue of Current Biology says there is no effect in either direction when comparing 83x S-cone contrast. The lights here are "pink" (which has a lot of blue) and "orange" which has very little. https://www.cell.com/current-biology/fulltext/S0960-9822(19)...
4. There is one important study in humans (Gooley 2010) that says we can be more sensitive to 555nm light after two days in dim light, so that mirrors this study. But this is not exactly comparable to the study cited here due to sensitization: it stands on its own due to the duration of the experiment.
It would be interesting if we could find some "truth" to the idea that twilight colors affect human circadian entrainment - it has been a recurrent idea for many years. We finally have the technology to target melanopsin separately from the S-cone (see Spitschan's work for an example).
For the press these results get, you'd be surprised that there has been extremely little research funding for most of these things in the last ten years. In a way, I hope that mixed results like these might help! How light affects us at lower levels, and how different we are from each other is not "solved" at all, so there is still a lot of work to do.
> There's extensive evidence that even relatively low levels of light harm sleep quality; blue light from white LEDs is particularly disruptive to circadian rhythm
sigh Fine, here are more articles. If you don't want to believe in peer-reviewed academic literature, I'm not sure why I'm bothering. Statistically significant results can be obtained with few participants. Behold the power of math.
Nocturnal light exposure impairs affective responses in a wavelength-dependent manner.
>Our results demonstrate that exposure to LAN influences behavior and neuronal plasticity and that this effect is likely mediated by ipRGCs. Modern sources of LAN that contain blue wavelengths may be particularly disruptive to the circadian system, potentially contributing to altered mood regulation.
Out of the lab and into the bathroom: evening short-term exposure to conventional light suppresses melatonin and increases alertness perception.
>Subjective alertness was significantly increased after exposure to three of the lighting conditions which included blue spectral components in their spectra. Evening exposure to conventional lamps in an everyday setting influences melatonin excretion and alertness perception within 30 min.
Non-visual effects of light on melatonin, alertness and cognitive performance: can blue-enriched light keep us alert?
Exposure to light at 6500K induced greater melatonin suppression, together with enhanced subjective alertness, well-being and visual comfort. With respect to cognitive performance, light at 6500K led to significantly faster reaction times in tasks associated with sustained attention (Psychomotor Vigilance and GO/NOGO Task), but not in tasks associated with executive function (Paced Visual Serial Addition Task).
[...]
Our findings suggest that the sensitivity of the human alerting and cognitive response to polychromatic light at levels as low as 40 lux, is blue-shifted relative to the three-cone visual photopic system. Thus, the selection of commercially available compact fluorescent lights with different colour temperatures significantly impacts on circadian physiology and cognitive performance at home and in the workplace.
This is very interesting. I think a lot of us have come to believe the claim that blue light exposure keeps you awake.
So what do we know? That excessive exposure to any kind of light at night keeps you awake?
It looks like there are several studies on the f.lux page discussing blue light specifically, but fair point that they could be cherry-picking just the studies that support their product.
> In the case of blue pumped LEDs he's referring to bulbs that use a short wavelength LED in combination with phosphor that absorbs the light and reemits it at lower, and broader, wavelengths.
This was part of my suspicion, but I'm not familiar enough to know if that was correct.
> I get the impression the writer's opinions are extremely niche.
I'll be the first to say "citation needed" to what I'm about to say, but I feel like we went through a cycle of "the science is clear: blue light is bad for sleep!" to "actually a lot of that was not good science", so I'm unclear of where the consensus actually is (if I ignore this article).
Yeah, these articles are missing the big picture. I've seen too many people cite articles like this while implying effectively that sleep and wakefulness somehow is not related to lighting at all, and that's utter nonsense.
Lighting is VERY relevant to sleep cycles, and there's no doubts about this anywhere legitimate. The most effective is to not ONLY use red-tint in display controls but also have dim indoor lighting AND dark red glasses (darker and redder than even the generic blue-blocking sort). And the effective is dramatic. Like really get sleepy with dim light. It's not subtle, it's about as strong as an effect can be.
Studying merely the question of whether a little more or little less blue affects eye health in terms of serious diagnosable eye conditions is completely missing the point.
> Blue light is a type of light that is emitted by the sun and by electronic devices, and it has been shown to cause strain on the eyes and disrupt sleep patterns.
In the research page linked, there is extensive research on the effects of bright light exposure to circadian rythms, which may indeed alter quality of sleep by altering natural biorythms (note that no effect is produced on sleep itself, but rather on its timing, and this in turn affects its quality).
There is, however, very little research linked to blue light in particular, and it is inconclusive and contradictory. The best source they cite is actually against the hypothesis:
"Occasional claims that the light sources with emissions containing blue light may cause eye damage raise concerns in the media. The aim of the study was to determine if it was appropriate to issue advice on the public health concerns. A number of sources were assessed and the exposure conditions were compared with international exposure limits, and the exposure likely to be received from staring at a blue sky. None of the sources assessed approached the exposure limits, even for extended viewing times."
On a more subjective note, how they bury the actual research below tons of related-but-not-really articles, pop media links, and "explanations" makes me suspicious.
And mind, I do set my screen to redder tones in the evening and find it pleasant and probably helps me set the mood to go to bed, but I don't think research supports physiological or health reasons to avoid blue light or spend money on blue light avoiding, as the OP link seems to say (I don't read German :(
At posting, I didn't have time to provide more references. You'll see I've given three more references below. Sources include Acta Physiologica, SPIE, and Neuroscience Letters. They discuss different effects of illumination color temperature in human systems.
I posted the initial reference as an entry point to follow literature on potential effects of illumination color temperature on human sleep, or perhaps circadian rhythms, through action on a hormone known to be critically involved in sleep. I didn't suggest it was the end of the story. My post was on topic and it contributed to the discussion.
Would be glad to review data you think interesting.
Andrew Huberman of Huberman Lab podcast discusses this in the first 4-5 episodes of the podcast. The takeaway is: it's late-night bright light, rather than blue light, that has effects on the circadian rhythm. It's an appeal to authority but I think I'll go with the professor of neurobiology and opthalmology on this one.
I found a study within a few seconds on Google Scholar which refutes OP's study.
Using google translate, i see this in the article (German translated to English):
"According to a recent study, contact lenses that block blue light do not provide better protection from eye fatigue than standard contact lenses than standard contact lenses (American Journal of Ophthalmology 2021; DOI: 10.1016 / j.ajo.2021.02.010), according to the DOG."
Several studies available at link above. Here's an example from what I found via google scholar query:
"All light is not equal: blue wavelengths are the most potent portion of the visible electromagnetic spectrum for circadian regulation. Therefore, blocking blue light could create a form of physiologic darkness. "
"At the end of the study, the amber lens group experienced significant (p < .001) improvement in sleep quality relative to the control group and positive affect (p = .005). Mood also improved significantly relative to controls. A replication with more detailed data on the subjects' circadian baseline and objective outcome measures is warranted."
From the article, "..we also noticed something rather curious: the colours that best passed through the glial cells were green to red, which the eye needs most for daytime vision. The eye usually receives too much blue – and thus has fewer blue-sensitive cones."
"Light from the Sun is strong in blue, short wavelength light ..when it comes in the evening or during the night, it fools the body into thinking it’s daytime. We now know that this bright blue light has the strongest effect on lowering melatonin during the night. Your tablet, phone, computer or compact fluorescent lamp (CFL) all emit this kind of blue light."
The scary conclusions they're drawing from this study seem highly suspect. How would one account for variables in humans such as diet, home environment, region, exposure to poorly understood chemicals.. the list goes on and on.
> 2012-2019: Watch out for that blue light, it's dangerous. Use f.lux.
> 2020: Nah, it's fine and not significant
> 2022: Actually teh blue light is very dangerous and will lead to HPV and cancer!
Emphasis on "may".
"Our findings suggest that using dim, cooler, lights in the evening and bright warmer lights in the day may be more beneficial."
Emphasis on "suggests".
Also, the study's title itself.
"Cones Support Alignment to an Inconsistent World by Suppressing Mouse Circadian Responses to the Blue Colors Associated with Twilight."
Emphasis on "mouse".
Science oozes back and forth. You should not strongly interpret individual studies. Debunked is a strong word here.
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