Evening use of light-emitting eReaders negatively affects sleep (2014)
pnas.org
pnas.org
Also, it was shockingly hard to find [for me], but the "light emitting ereader" referred to in the title was an Apple iPad. It's not specified what kind of iPad they used, and the study focussed solely on reading from the iPad vs reading from a printed book.
The authors do note (in Table S1, in the Supporting Information) that they don't consider a Kindle e-reader to be light-emitting.
(I'm not throwing shade (heh) at the study, just adding some pertinent information that I thought would be useful to know.)
It would be interesting to see a study especially since the tech is so different.
"Third, in the present study, the LE-eBook was set to maximum brightness throughout the 4-h reading session"
I used to use it daily just before going to sleep, but then found the app I read with has a white text on black background that I prefer. Using both at the same time makes it too dark for my eyes, which is a good problem to have.
Burying that lede several sections deep feels almost purposely misleading, either that or just incompetent in my opinion.
> The LE-eBook was set to the maximum brightness setting.
Others on this thread have pointed out that it's an iPad.
For years now, this has seemed like common sense to me. Of course you don't want to blast a tablet or laptop screen at 100% brightness when you're trying to get your brain to fall asleep.
I use a Kobo e-reader with its brightness set to 1%. I can't imagine that exposes my eyes to light amplitudes that would exceed that of a lamp. In a dark room I don't have any problem reading the words, and I don't think I've had any sleep problems.
I will stay up nearly indefinitely in bed if I read my phone or iPad. Read the same material on my Kindle Paperwhite and it can be difficult to stay awake more than a few minutes.
I don’t know if it has anything to do with the difference in screen types, as my Kindle does have a backlight but it is so night and day for me, I am predisposed to believe anything that states there is a mechanism for my experience.
Also, it might have to see with the level of blue light that is emitted by those devices. Light in backlit screens is somewhat filtered and might not contain as much blue.
"The randomized, crossover protocol design consisted of two conditions: (i) reading an LE-eBook (iPad; Apple Inc., Cupertino, CA) in otherwise very dim room light for ∼4 h before bedtime for five consecutive evenings, and (ii) reading printed books in the same very dim room light for ∼4 h before bedtime for five consecutive evenings"
In other words, they compared using a tablet to reading a book. Unsurprisingly, they found that using the tablet negatively affects sleep.
——
Note that maximum brightness on an iPad is intended for reading in direct sunlight.
In my experience backlit screens contain a lot of blue. I have been able remove the waking effect of my screen entirely using a heavy red filter provided by f.lux. But with the default settings, and even Apple's night shift implementation it's very blue. It is slightly less bad on newer devices that support "TrueTone".
I used to have a hard time waking up, even with alarms.
Now I just reach for my phone while I'm still half asleep.
The bright screen wakes me up every time.
I've noticed the same thing! Glad to see I'm not nuts...
The intensity of light needed on an iPad to read comfortably is much higher then a backlit eInk reader e.g. a Kindle Paperwhite. Personally it doesn't affect me very much on such devices, but it would be interesting to see if there is a noticeable difference.
Personally I define something to not affect my sleep, when I got trouble staying awake after one or two chapters on a workday.
PRS-350 (no light eink): Like a real book, it mostly depends on the light setup of the room. With a warm, indirect and just enough to not have trouble reading dim light, I easily get sleepy and in trouble to stay awake long enough to poweroff device and lamp. I did fall asleep with device in hand often enough, even on a plane once.
Aura HD (light layer eink, one of the first gens): Had to stop myself reading often after looking at the clock or how many chapters I read. Just one more chapter, was a real problem with it. But I didn't had any trouble falling asleep after putting it away.
Note10 kobo reader (amoled, red text on black, "background light off mode"): Need more time than PRS-350 or real book, but I definitely got trouble keeping my eyes open after a while. Sometimes I switch it off and already fall asleep before I get the chance to put the phone out of my hand.
Note10 anime reader app/websites/etc: Even without videos or other animated/interactive media, I stay awake indefinitely. If I fall into that trap, it is common for me to stay awake to at least 2am, sometimes up to 5am.
That would be close to painful and certainly very unpleasant in a dim room at night.. WTH were the study authors thinking?
The iPad won't even do that without the user manually setting it up to do that, and almost no one is going to find it comfortable.
It seems more like they were trying to set the conditions to get the result they desired. They could have shined an LED flashlight into the user's eyes and gotten the same result.
They were thinking that they wanted a publishable result.
Unfortunately, little to no difference on sleep between dim e-reader at night vs book and dim light wouldn't get published even though would be really useful to know.
On the other hand, maybe there is some filtering taking place when light is bounced off materials. I.e. blue wavelengths being absorbed by the paper.
A paper[1] funded by NIH published this year showed that ~12 log photons cm⁻² s⁻¹ on λ=460nm is enough to suppress melantonin production.
I've discussed more on sibling thread.
[1] https://journals.sagepub.com/doi/pdf/10.1177/074873041558541...
Almost certainly from my own anecdotal experience. There's a reason why bedroom lights tend to be warm (even though they're often now leds)
As today, the academic consensus is that Melatonin suppression, on the lower part of the spectrum, is regulated by melanopsin produced by the Intrinsically photosensitive retinal ganglion cells (ipRGCs) -- not blue rods. The photosensitivity of ipRGCs has λ_peek = ~460 (nm).
They've done experiments with rats without cones and rods (but with ipRCS), and they displayed circadian cycles.
Melatonin is also suppressed by lights on higher part of the spectrum, but haven't papers on it.
I've decided in getting this safety glass: https://www.thorlabs.com/thorproduct.cfm?partnumber=LG3A
The dark amber glass from swanwick have similar optical density curve: https://www.swanwicksleep.com/
I choose the safety glass instead of the swanwick glass because I have more confidence that a safety glass in conforming with the provided specification. Since I intend to use it home, I don't care about how it looks.
It you want to customize your own glass, this company sells lens blank of filter that block a somewhat similar wavelength to the other products: https://laserprotection.com/product/laser-pointer-protective...
Zeiss also sells special lens for colorblind that blocks similar spectrum. But it is very hard to find information on how to get them online.
If I'm reading in a darkened room on my kindle I have the brightness on the kindle set lower than it's possible to do so on an iPhone or iPad.
I think this is common, which shows how crazy it is the study had an iPad on maximum brightness and had the user read for hours in that configuration. I'd have red eyes and a splitting headache by the end of that which would of course have negatively effected my sleep.
It works wonders for me, honestly, I find I fall asleep easier with reading on a not-bright e-ink reader. I also have a kobo reader which is more yellow in its hue, but also a tad brighter. That one also works well for me, I usually put the reader down in 10 minutes to sleep.