Blue light may not be as disruptive to sleep patterns as thought: mouse study

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:

1. The Thapan study from 2001 indicates extra blue-light sensitivity in addition to melanopsin. Lights are seen for a half hour at night. https://doi.org/10.1111/j.1469-7793.2001.t01-1-00261.x

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)...

3. The Brainard 2015 study compares 4000k to 17000k lights: at the same "melanopic" level the 17000k lights do a lot more melatonin suppression: https://jdc.jefferson.edu/cgi/viewcontent.cgi?article=1081&c...

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.

With flux/redshift on, that doesn't happen. Blue light may not be keeping me up, but it definitely fucks my brain up in some complicated way.

I've noticed that I tend to get sleepier at night which is great as before I would have to force myself to go to sleep (I'm a natural night person.)

I've also noticed a small increase in my distance visual acuity (subjectively measured by me using an eye chart so not the most accurate.) I have read that intense outdoor light protects against myopia (see https://www.ncbi.nlm.nih.gov/books/NBK470669/) so I suspect this is related.

In studies both green and blue light showed to be the least disruptive (but green is better for night sight). I thought this was strange since it was always believed that blue light is bad.

But it appears this article agrees.

Edit: a lot of plants and corals are grown under red light. So maybe red could be more harmful for your sleep if it triggers growth.

Seeing how differing everybody's experiences seem to be, maybe this is one thing where people are just different from each other.

Thanks for posting this. Very interesting read and has made me change my buying behaviour.

Another issue is that, as others have noted, a lot of people's experiences are with Flux, but Flux is an incomplete solution to the blue light problem. I use a Macbook Air: Flux changes the color temperature of my screen, but directly below my screen is a backlit keyboard which is very, very blue. It was a big turning point for my sleep health when I got a pair of blue light blocking glasses which handled this in addition to the screen blue light.

Also, waiting for all the anecdotal comments 'Yeah, it makes sense. Best sleep I get is after I use my devices without f.lux' to flow.

It doesn't help with the desire to actually go to bed, but another anecdote is the darker the room the better the sleep. Most window dressings are decorative and designed to be somewhat translucent. Add a blackout cellular shade or curtain. Eliminate any displays, cover power LEDs etc.

The night modes of my displays (iMac, MacBook Pro, iPhone, iPad) definitely help me be a bit more relaxed compared to staring at them in their normal mode, especially during the nights.

That being said, reduction of blue light does not help that much either. I found that a much stronger contributor to my staying awake is the light of the screen itself. I found that if I am in the mood to nap during the afternoon, the smaller difference between the my phone's display light and the ambient light helps me fall asleep much, much quicker compared to when I am staring at my phone with all lights turned off. The difference is much more pronounced and obstructs my brain's desire to doze off.

So IMO the reduced blue light has an effect. But it might not be that big indeed.

Relatedly it always bugged me when I was little that blue lights seemed "white in the middle with turquoise then finally blue exterior". Blue lights just couldn't be both bright and saturated very easily. I wouldn't be surprised this is related to the daylight-ness vs twilight-ness.

    2010: Study says caffeine is unhealthful 
    2011: Study refutes 2010 caffeine study
    2012: New study says caffeine is unhealthful 
    2013: New study says caffeine is safe
    2014: Etc.

The yellow LEDs in the room don't bother me when I forget to turn the device off. And the red clock projected onto my ceiling doesn't bother me either.

I used to sleep fine with blue LEDs though, so maybe it's just different for different people, ages, environments, and/or other factors.

I feel like this is the new "wellness" science that sounds good in practice, but lacks evidenced based studies.

As all things, it's a spectrum but the press has to be sensationalist about it.

But sure, let's drop this tiny snippet of information, after all it will drive clicks, am I right??