E-ink fans can probably relax

Do e-readers really harm sleep? Depends what you call an e-reader

Stay on Top of Enterprise Technology Trends

Get updates impacting your industry from our GigaOm Research Community
Join the Community!

A new study has claimed that light-emitting e-readers “negatively affect sleep, circadian timing and next-morning alertness” when used in the evening. However, those reading the resulting coverage should look into the details before worrying too much.

The study was published Monday in the Proceedings of the National Academy of Sciences (PNAS), leading to scary headlines such as: “E-readers ‘damage sleep and health,’ doctors warn” (BBC); “Keep That E-Reader Out of Bed and You’ll Feel Better in the Morning” (Pacific Standard); and “Before Bed, Switch Off The E-Reader And Pick Up A Paperback” (Fast Company).

The key problem with this study and the more alarmist stories that followed, is that when it says “e-reader”, it means “[company]Apple[/company] iPad”. An iPad at full brightness, no less. When I hear “e-reader”, I tend to think “dedicated e-reader” – an e-ink device without a backlit screen — rather than a multi-purpose tablet. And there’s a big difference.

The screens of devices such as tablets and smartphones have long been known to emit short-wavelength light, also known as blue light. All light can suppress the secretion of melatonin – the hormone that controls our day-night cycles – in the evening and night-time, but blue light has a particularly pronounced effect and previous studies have shown that it’s best avoided at night.

The new study, conducted on a small group of 12 participants, adds to these earlier studies by comparing the effects of a light-emitting “e-book” (iPad) with those of a paper book. The researchers found printed books were definitely safer, writing:

The use of light-emitting electronic devices for reading, communication, and entertainment has greatly increased recently. We found that the use of these devices before bedtime prolongs the time it takes to fall asleep, delays the circadian clock, suppresses levels of the sleep-promoting hormone melatonin, reduces the amount and delays the timing of REM sleep, and reduces alertness the following morning. Use of light-emitting devices immediately before bedtime also increases alertness at that time, which may lead users to delay bedtime at home. Overall, we found that the use of portable light-emitting devices immediately before bedtime has biological effects that may perpetuate sleep deficiency and disrupt circadian rhythms, both of which can have adverse impacts on performance, health, and safety.

These effects could be serious. As the researchers note, recent evidence has linked chronic suppression of melatonin secretion by nocturnal light exposure with “the increased risk of breast, colorectal, and advanced prostate cancer associated with night-shift work… which has now been classified as a probable carcinogen by the World Health Organization.”

But again, there’s a huge difference between an iPad and an e-ink reader such as those in the [company]Amazon[/company] Kindle, [company]Kobo[/company] or [company]Barnes & Noble[/company] Nook ranges. The study does not once mention e-ink e-readers. The iPad was also “set to maximum brightness throughout the four-hour reading session, whereas, by comparison, the print-book condition consisted of reflected exposure to very dim light.”

Charles Czeisler, director of the Division of Sleep Medicine at Harvard Medical School, who co-authored the study, told the Washington Post that the “standard Kindle” would provide an exception to the study’s findings as it does not emit light and was more like reading a paper book. A Vox interview with lead author Anne-Marie Chang suggests that the research was conducted between 2010 and 2011, when even the original, non-illuminated Kindle was pretty new and paper books made a better point of comparison.

There has been no mention at all of e-ink readers that are not backlit but that are illuminated, such as the Kindle Paperwhite or Nook GlowLight — which is not surprising as these devices were only introduced in 2012. Rather than lighting the screen from behind, illuminated e-ink e-readers are “front-lit” and use small LEDs around the screen, pointing inward rather than outward, to cast a glow over it (the Paperwhite channels this through “light guides” to illuminate evenly). This is more like looking at an earlier Kindle in a lit room, than it is like looking at a light shining directly into your eyes.

What’s more, these devices generally allow users to dim the light – and so do blue-light-tastic backlit tablets, for that matter.

So in short, yes, you should avoid staring at your smartphone or tablet (or PC or TV) for hours before trying to nod off. And that includes the Kindle Fire, which is after all just a tablet. But let’s give dedicated e-ink e-readers, which are very different devices, the benefit of the doubt until someone proves they also pose a danger.

19 Responses to “Do e-readers really harm sleep? Depends what you call an e-reader”

  1. so glad this article is getting out there…way too many shilling bloggers trying to get hits by scaring people…hopefully the simple masses will go get their Kindles out of the trash now!

  2. travelblips

    I read on my front lit kindle for anywhere between 10 mins and 2 hours, with it dimmed down to a very dull grey-green. I’m sure it’s not the best but I certainly haven’t noticed any sleep issues.
    And kudos to the author for noticing that the experiment was done on an iPad! Dangers of reading on then has been known for a while! I thought it very misleading the study called them ‘e-readers’ when they are backlit led tablets for goodness sake! And who could red on that for 4 hours on brightest light??? One hour at half light hurts my eyes!

  3. Backlit may be worse, but if the light is blue, even if not backlit, this will affect melatonin. Best to use bug lights for ambient lighting and proper orange safety glasses. Do a test on your own sleep patterns. The cost of the experiment is low. The potential benefits may be huge.

  4. Four hours of reading before bed? Seriously? If you’re focused on reading as the task, how about studying a more reasonable 15- to 30-minute session. Ok, so expand the definition of “reading” to all uses of a tablet (email, surfing, netflix, even reading), but even then? Four hours? Huh. My home study of one is hard-pressed to find four hours to devote to sitting still between the time that all the post-work stuff is done and bedtime.

  5. Bob Friedman

    The culprit is the blue light emitted by the LEDs in the device. LEDs in these devices shine a lot of blue light. The other colors to make white are accomplished by having the blue light excite phosphors for the other colors. So even if through software you modify the perception of the screen’s color, you may still be getting a lot of short wavelength blue light.

    Reading a printed book or an eInk device with a light that shines a lot of blue light (ex. LED lights, CFLs, etc) will end up reflecting blue light back to your eyes.

    You either need a light source that doesn’t have much blue light (ex. candle, incandescent bulb, red LEDs), use a blue-light blocking filter on the light source (screen filter, lights that come with orange or red filters), or use orange goggles to filter the light before it hits your eyes.

    So, we know that blue light is a problem at night. What still does not seem clear is how much exposure to blue light is a problem. Is the blue light level of an incandescent bulb OK or is that too much? Is a half hour exposure to an unfiltered LED book light too much or OK? If an e-reader with a built-in light is set to a very low brightness, will that still create a problem if read for just 30 minutes?

  6. The study is pretty weak. Limited sample size, 4 hours a day at full brightness?

    I really expected better out of BWH than to publish a study that’s 3 years old and turn it into the academic medicine version of clickbait (gotta love Dr. Czeisler’s laundry list of conflicts.)

  7. Ian Smith

    What type of light was used to illuminate the paper in the study?

    We have a choice these days. It used to be incandescent, but they are outlawed, so which is better: halogen (for while longer), fluorescent or LED?

  8. Also note the fundamental differences in study setup between “LE-eBooks” and print books – not exactly how anyone uses an ebook reader: ” During LE-eBook
    reading sessions, the light-emitting device was set to maximum brightness
    and placed in a stand that held it at a fixed angle. This stand was placed on
    a table directly in front of the individual at a 30- to 45-cm distance from their
    eyes. Participants were allowed to turn pages on the LE-eBook, but were
    asked not to hold it while reading or make any adjustments to the settings.
    During the printed book reading sessions, participants were allowed to hold
    the book at any desired distance from their eyes.”

  9. Michael W. Perry

    Ah, another Amazon fanboy speaks up, and about an epaper Kindle no less. You can tell that from the strained argument. While even die-hard Obama fans are growing disgusted with him, for Amazon’s fanboys, the Big A can do no wrong. It’s like Microsoft in the mid-90s.

    Nonsense. A lot of apps on my iPad, let me switch to a dark screen mode (i.e. grey letters on a black background). As far as I know, my sister’s Paperwhite Kindle can’t do that. Not only that, her Paperwhite screen is clearly that terrible-for-sleep blue light not actually white like my iPad. And the backlit versus reflected light claim makes no difference. Photons are remain photons. Intensity matters, but both devices allow the brightness to be turned down. That’s what users should do.

    Changes do need to be made to all these devices. Amazon should make a Paperwhite that has a red-lit mode for bedtime reading. And iPad app developers should add a red mode to their black modes. Apple might even want to build such a mode into iOS. It’d be great to use an iPhone at night without destroying night vision.

    And last but not least, these researchers should work with the latest set of devices under realistic scenarios not four-hour sessions and fully lit screens. That suggests trying to force the data to yield a specific, anti-tablet result.

    For now, my fix is to do bedtime reading lit by a 1-watt red LED bulb I picked up at Home Depot for under $4. Placed in a reflector fixture at the head of the bed, it provides just enough light for reading (paper books or my non-lit Kindle 3) and for getting about the room. I even use it to provide a sleep-inducing red background to my iPad reading. And it seems to help.

    • Bryan Redeagle

      I’m not sure you read the article thoroughly… His argument wasn’t that Amazon’s products are an exclusion to the research, but that the e-readers that use e-ink displays should be an exclusion to the research (which is even mentioned by a co-author of the research).

      Further, your iPad’s white-looking light is still short-wavelength light. Dark-mode or not, you’re still getting that light in your face.