Scientific study compares bedtime reading risk from iPad, iPhone, PW1

Scientific study compares bedtime reading risk from iPad, iPhone, PW1

Oh, I’m very interested in your feedback on this one!

I’ve written many times about the difference between how a

All-New Kindle Paperwhite, 6″ High-Resolution Display (300 ppi) with Built-in Light, Wi-Fi – Includes Special Offers (at AmazonSmile*)

or other frontlit device (the Voyage, and some other EBRs…E-Book Readers) versus how a backlit tablet, like the

Fire, 7″ Display, Wi-Fi, 8 GB – Includes Special Offers, Black(at AmazonSmile*)

or other backlit devices (the other Fires, a SmartPhone, a computer, a TV, and so on)

work, in terms of lighting.

On a backlit device, the lighting is behind the screen: what you see is between your eye and the light source.

On a frontlit device, the light is on the same side of the screen that you are. A light is pointed at the screen and bounces off…the same way that you can read when using a desk lamp, or the sun.

I find the Paperwhite and Voyage to be the most comfortable reading experience I’ve had…including paper.

A lot of people are concerned about how reading on a screen may be affecting their sleep habits. They have heard about “blue light” keeping them up at night, by messing with your biological system (perhaps they have heard that melatonin is involved).

I’ve always believed that the Paperwhite was not as bad…that reading on my Fire in bed would be more likely to keep me awake than reading on my Voyage.

Well, there’s now been a scientific study which produces some interesting and specific data…but I’m not sure I follow or agree with their conclusions:

Bigger, Brighter, Bluer-Better? Current light-emitting devices – adverse sleep properties and preventative strategies by Paul Gringras, Benita Middleton, Debra J. Skene, and Victoria L. Revell in Frontiers of Public Health

They tested the light emissions from an iPad, an iPhone, and a Paperwhite first gen. You can read the specifics of the models…I want to encourage you to look at the original report.

Here is a sort excerpt from the results:

“All the LE devices shared very similar enhanced short-wavelength peaks when displaying text. This included the output from the backlit Kindle Paperwhite device.”

That’s right: they found that the Paperwhite and the iPad had similar outputs in a measurement they suggested would negatively impact your sleep.

Many of the measurements they did were quite different for the iPad and the Paperwhite…about an order of magnitude (ten times) different. However, I guess those aren’t the wavelengths they consider impactful.

They also tested two remediation strategies: one hardware, one software.

The hardware one was for the user to wear goggles that filtered light.

The software one was to have the device go into a “sleep mode”, and shift the colors of the output.

Obviously, asking people to wear goggles to bed would not be an easy cultural  shift. If we could get people to do that sort of thing, they’d be wearing helmets when driving their cars…that would save a lot of lives, from what I’ve heard. 🙂

The software fix makes more sense to me.

I love that the “nightstand” clock on my now discontinued Kindle Fire HDX 7″ has red numerals!

I have superior night vision, which may be connected to my color vision deficiency  (“partial colorblindness”). When my Significant Other first met me, the light on my nightstand was a 25 watt red lightbulb…that was plenty for me.

So, I know I’m not typical. 🙂

I know, though, that a color shift could matter to even me as to how bright a light seems.

I have to say, my Voyage does not seem like it is keeping me up at all. I read a few “pages” in bed, and I’m ready for sleep…well, there is a big nighttime routine before that that is about half an hour, but the Voyage doesn’t seem to keep me up any more than a p-book (paperbook) did…less, I’d say.

My guess is that we may see a mode like this in the future, touted by the device manufacturers. There are all some things that do this, some settings on some computers, some apps.

My sense of the study is that their methodology for gathering the technical data was reasonable, for a small sample.

I’m not sure that that data does, though, cause the problems they suggest. I’d like to see studies with people actually using a frontlit device versus a backlit device and how it affected their sleep.

Oh, that’s one other thing: the study refers to something some of you already noticed…they say the Paperwhite is a backlit device, and it’s not. That doesn’t make me doubt their measurements, but does show a certain…lack of precision.

What do you think? Have you noticed any difference if you switched from a backlit device to a frontlit one when reading before going to sleep? How does it compare to reading with a nightstand light? If you do read the journal article, feel free to tell me and my readers what you think about it by commenting on this post.

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* I am linking to the same thing at the regular Amazon site, and at AmazonSmile. When you shop at AmazonSmile, half a percent of your purchase price on eligible items goes to a non-profit you choose. It will feel just like shopping at Amazon: you’ll be using your same account. The one thing for you that is different is that you pick a non-profit the first time you go (which you can change whenever you want)…and the good feeling you’ll get. :) Shop ’til you help! :) 

This post by Bufo Calvin originally appeared in the I Love My Kindle blog. To support this or other blogs/organizations, buy  Amazon Gift Cards from a link on the site, then use those to buy your items. There will be no cost to you, and a benefit to them.


26 Responses to “Scientific study compares bedtime reading risk from iPad, iPhone, PW1”

  1. Clint Bradford Says:

    Not entirely sure about this study … But I sure know it makes a difference in “eye/head health” between using a device with a white frame versus a dark-colored frame. I can give myself “discomfort” in less than an hour reading on a white-framed device (like my old Kobo). But I can read for hours on end with a dark-framed device. Manufacturers of “screened” devices know this: How many TVs do you see at Best Buy with WHITE frames? (grin)

    • Bufo Calvin Says:

      Thanks for writing, Clint!

      I’ve seen other people mention that…some people put dark “skins” on their white Kindles for that reason.

  2. Mightyh Says:

    Unfortunately, it seems my Voyage is even better at putting me to sleep than my Paperwhite was. Maybe it’s the automatic “just right” amount of light it puts out.

    It’s such an awesome feature but I find it almost impossible to take advantage of it.

    • Bufo Calvin Says:

      Thanks for writing, Mightyh!

      I don’t use the automatic brightness setting…generally, it makes it brighter than I would like it. That’s also an issue with tablets, because the brighter the setting, the faster that it uses battery charge.

      • D. Knight Says:


        You can adjust the automatic light setting in the Voyage. (It was too bright for me to begin with, too.) Just turn auto brightness on, and when it’s setting is too bright, adjust it to the level you like. You’ll have to do this several times and for every external light setting you are typically in, but eventually it’ll use the settings you like. After that, it’s really nice.

      • Bufo Calvin Says:

        Thanks, D.!

        I’ll give it a try! I appreciate that!

      • Clint Bradford Says:

        I run Display Brightness on my Fire HDX to read at night – white type on black background. Even the default “minimal” brightness with no other lights on in the room is, to me, a little harsh Display Brightness takes it down a notch.

  3. Alan Church Says:

    Bufo and readers,
    As a psychologist who has studied this for many years I can tell you that it is well known in the scientific world that blue light at a particular point of the spectrum suppresses melatonin production and leads to impaired sleep for many if not most people. There are many scientific studies which attest to this,some of which are referenced in the article you mentioned. I see no reason to doubt the results of that study because the authors were unaware that the kindle is front lit.
    Please note that studies have shown that Wikipedia is very accurate with regard to its science articles.
    There are a number of products used by psychiatrists, psychologists and other health professions to treat insomnia , depression and other conditions which take into account light, melatonin, and circadian rhythms. You can find info about these products as well as the conditions, and even get advice from a doctor at this site: Many people do indeed wear amber glasses (not goggles)for several hours before bedtime and report being able to sleep better. You can buy them here: This company also makes blue light filters for iPads. In fact, I am expecting some in the mail any day. I will email the scientists at the company and tell them about this study and suggest they make filters for the Kindle ereaders..
    Thanks for bringing this to my attentions I will cover my readers with filters at night now as well as my iPads. Any of you with sleep problems should consider investigating this.
    Alan Church Ph.D.

    • Bufo Calvin Says:

      Thanks for writing, Dr. Church!

      I appreciate that insight!

      I agree: I wasn’t doubting the validity of the study because of the error about the hardware…it’s not directly relevant to their measurements.

      I, in turn, was imprecise by using the term “goggles”.

      Having the filters for EBRs would also allow a good study, particularly since I would think you could do a “placebo” version fairly easily…something I would want to see in a study like this.

      Again, I appreciate that you were able to share much more context for this study with me and my readers!

    • Allie Says:

      Alan, thanks for this.
      I am *extremely* light-sensitive, which, in my case, goes hand-in-hand with insomnia. (I am often interested in studies and so forth but I KNOW, all the way back to my teenage years on AOL, that staying on a regular backlit screen keeps me up. It just IS — and it’s really irritating! Inconvenient, also.)
      When I recently found myself in need of reading glasses – but not yet bad enough for prescription lenses – I ended up getting a pair that claimed to filter blue light. Mostly I liked the frames 😉
      Perhaps I’ll give them a try so I can work on the computer closer to bedtime. However, they are still cheap reading glasses so perhaps I should look into something else.
      I have one question for you, Alan, which is, are you affiliated with either of the two websites listed here? Please don’t be offended by my question. I don’t have a problem if you do; I am simply curious. Each site you mention seems to have quite a lot of info to sift through.
      Either way, I very much appreciate your comment here.! Best to you.

      • Bufo Calvin Says:

        Thanks for writing, Allie!

        I appreciate the light sensitive part. 🙂 I really don’t like “ready lights” on appliances…why does there have to be a light on all the time? In the bedroom, we have a piece of cloth over the ready light on the TV. I don’t charge my Sonicare toothbrush at night, because it flashes…even though it would be in the bathroom at an oblique angle.

        One famous story in my family is me being in the kitchen in the middle of the night, and someone (either our kid or my Significant Other) turning on the light…and me collapsing to the floor with my arm thrown over my eyes, like Dracula at sunrise. 😉

        I can fall asleep with lights on, that’s okay. It’s if I wake up in the middle of the night and there is a light on which brings me to consciousness…then going back to sleep might be hard.

  4. jjhitt Says:

    Contemporary “white” LEDs are actually blue emitters with a phosphor coating that glows white when stimulated by blue light. It’s inherent in the technology that the light is going to be somewhat blueish.

    They need to progress to human subjects (or book reading apes) to determine what, if any, biological impact there really is.

    • Bufo Calvin Says:

      Thanks for writing, jjhitt!

      I don’t think it would be this group doing that study, but if someone hasn’t, they likely will. 🙂

      By the way, my sibling’s service dog reads a few words…really!

      You start out with symbols: a triangle might mean sit, a circle might mean “down”, that sort of thing.

      You can then associate the symbol with the written word.

      Why do that?

      It could help someone else communicate with the dog…it’s possible my sibling may eventually not be able to speak.

      One funny thing, and apparently this is not an uncommon behavior, although they aren’t sure why dogs do it, from what I know. When the dog was first learning the symbol (at that point, associated with a vocal command), the dog would first give the card a head butt before carrying out the command! It doesn’t have to do with seeing it better, obviously…but it is something a lot of dogs do.

  5. Lady Galaxy Says:

    I was wondering if the study took into account the different levels of brightness. I turn the auto function off on my Voyage and set the background so that it’s the same shade as the background on my Kindle Keyboard.

    I’ve had irregular sleep patterns since birth. Even when I was an infant I’d stay awake half the night. I spent most of my adult life with chronic sleep deprivation because no matter how many years I had to wake up at 6:00 AM to get to work on time, my body never adapted to falling asleep before midnight.

    I went through a sleep clinic about 20 years ago. They diagnosed me with a sleep disorder with a name too long for me to ever remember. At the time, I was teaching elementary school. Their advice was for me to take a job working second shift. I tried to explain to them that there weren’t any jobs like that for elementary school teachers.

    Now that I’m retired, I got to bed around 5:00 AM and sleep until around noon.

    • Bufo Calvin Says:

      Thanks for writing, Lady!

      This is what they said about the brightness:

      “The brightness levels of the screens were not adjusted for those devices that had an automatic setting (iPhone 5s and ipad Air) but the Kindle Paperwhite screen brightness level was reduced to 50% (guided by “typical night time settings” feedback from a convenience sample of 10 Kindle Paperwhite users). For each device, the irradiance as an exact spectral power distribution (SPD) was measured using the same calibrated spectrometer (Ocean Optics BV, Dunedin, FL, USA).”

      I think that constitutionally, I am a night person, but…

      My weirdest sleep schedule was when I was sleeping from 1 AM to 5 AM and from 1 PM to 5 PM. That worked, but I didn’t have much social contact outside of my “day job” and my theatre work. I would wake up at 5, eat breakfast, get ready in a hurry, and get to my day job from six to noon. Then, zoom home, eat lunch, go to sleep at 1:00 PM. Wake up at 5 PM, have call at 6, finish up with the theatre around 11:30, back home, eat again, to sleep by 1:00 AM.

      For quite a while, I would be asleep by 9:00 PM, and wake up at 5:00 AM…the classic eight hours. Within the two years or so, it’s changed a lot…it’s over the same period where I’ve lost about forty pounds (in a good way), but that could be coincidence. Anyway, I normally go to sleep by 9:00 still…but usually wake up between about 2:15 AM and 3:30. I talked to my doctor about it…I said that in my job, if I was suffering cognitive decline, I’d know it. 😉 I’m also not falling asleep during the day.

      It does give me more writing time. 😉 However, my baseline for exercise is 90 minutes a day, and it’s actually usually more than that…and I wasn’t doing that, oh, three years ago.

      • Lady Galaxy Says:

        I’ve never had a split sleep schedule, but I once had a split work schedule which interfered with sleep and life in general. I worked at a business college for one semester, and I was on a split work schedule. I had morning classes from 8:00 AM until noon, and then evening classes from 6:00 to 10:00 PM. I was thrilled when they decided to consolidate classes, and as last one hired I was first one released. That was such a relief because I was going to resign anyway. At least being “riffed” left me eligible for unemployment benefits. It also meant I was available to take the substitute HS teaching position that led to a permanent teaching job in the district where I had subbed. That position was offered on a Friday the 13th after I had walked under a ladder.

      • Bufo Calvin Says:

        Thanks for writing, Lady!

        That’s a good demonstration of how most things have good and bad elements…thanks!

  6. Alan Church Says:

    Lady Galaxy,
    You were probably diagnosed with Delayed Sleep Phase Disorder(DSPS), which you seem to still have, as do I.-see info here-

    I am a psychologist but not an expert on sleep, though I have been reading about it and trying various remedies for years. Many sleep clinics are not able to effectively treat it. Relatively new treatments, at, would be the easiest if they are effective for you. They were not for me unfortunately but are for many. The blue blocking glasses are a simple and inexpensive fix (about $80) if they work. Also low dose melatonin. Bright lights may be involved also. You can do an online self-assessment here-
    This will give you a diagnosis and what to do next.

    On this page at the site you can “ask the doctor” about your problem(if it is a problem still) and get an answer in a day or two. The people at this site are the top people in the world on this subject. One of them discovered Seasonal Affective Disorder decades ago and developed the treatment of bright lights in the am to treat the depressive phase, often effective for seasonal depression.

    The best treatment for sleep disorders is
    Cognitive Behavioral Therapy for Insomnia (CBTS), provided primarily by psychologists. According to the research it really works, and is better than any other treatment. It does require work on the patient’s part but is more effective than drugs. I’ve read about it in many medical newsletters so it’s not just psychologists who recommend it. I went to a sleep clinic with my DSPS and was told they had no treatment for it. Medication helps but also harms. CBTS works and leaves you drug free. If the glasses work that’s easier and cheaper so I would try that. Or if you like things the way they are you can do nothing. Now that you are retired maybe that is best. Who is to say that being a night owl is bad. Perhaps it’s only if you have to get up early that it’s a problem.
    Bufo, I’ve never of a schedule like yours. Amazing. Having followed your blog for years I marvel at your level of productivity. I’m so glad to be retired and don’t have to do so much.OY!

    I agree that a trial with human subjects on ereaders would be a good idea. Though the effect of blue light, which is in the white light spectrum, is well established as being disruptive of sleep, I’m not sure how intense it must be. I’ve had the impression that any amount will be disruptive but perhaps it is dose-related. Phones and iPads may be worse than ereaders. Ereaders on dim may not be disruptive much, if at all. For some of you that seems clearly to be the case. But, like studies with caffeine, it may be disruptive and you are not aware of it. Only studies with human subjects will answer this. Anecdotal evidence is not useful. Though personal experience can be compelling the conclusions are often wrong.
    Alan Church Ph.D.
    Sent from my iPad

    • Bufo Calvin Says:

      Thanks for writing, Dr. Church!

      Well, that split schedule was a long time ago. Now, my normal thing is that other one I mentioned: asleep at 9:00 PM, up between 2 and 3:30.

      I’m not sure who would do a study…although I could see it being done by college students in a class. I aways like to see a study done with the scientific method…however, I also enjoy reading anecdotes. I just don’t find the latter as convincing.

    • Lady Galaxy Says:

      That sounds about right. Unfortunately, I can’t take melatonin because it is an immune booster, and I have an autoimmune disorder, myasthenia gravis. Bright lights wouldn’t work for me since they trigger migraines. When I was teaching, I’d have to keep at least one of the rows of overhead fluorescent lights turned off. None of my students ever complained that the room was too dark. In fact, quite a few commented that they were more comfortable in my room because it wasn’t so flooded with light. I have a small living room which I consider to be well lit with single 30 watt incandescent bulb.

  7. Zebras Says:

    I, too, have crazy sleep patterns. Currently bed at 2 am wake up at 7:30 am. Random naps especially after husband puts sports on to make up the extra required sleep. Almost can’t fall asleep at night without reading something. If I read on my Fire, I’ve noticed I stay awake a lot longer then when I rad on a kindle.

    My eyes are opposite of yours with terrible night vision. I haven’t found a setting that works at night reading with the voyage with the lights out. I think it still makes reading in bed easier. Sitting up in the dark is Ok. I think my eyes close up vision are at different levels and I think my worse eye is the one predominant when I am lying down on my side.

    I did not know the auto adjusting light on the voyage would learn our preferences, so thanks D. Knight for that tip.

    • Bufo Calvin Says:

      Thanks for writing, Zebras!

      Everybody seems to have bad night vision to me, so it’s hard for me to judge that in others. 🙂 I’m sorry you have the troubles you do!

  8. Alan Church Says:

    No,I am not affiliated with either or any website or any product, just a private citizen. Yes, there is a lot of information to sift through.

  9. Alan Church Says:

    Here is an article from Harvard medical School with some easy to follow advice on avoiding blue light at night.
    I have no association with Harvard :mrgreen:

  10. Alan Church Says:

    Problems associated with computer screens- some people experience eye problems from looking at computer screens.for some it can be serious. A couple of months ago I researched this online and decided to try some glasses since I spend many hours each day with an iPad. While I experienced no problems I was aware of, it seemed from my researches to be a good idea. I claim no special expertise in this area. I would just say that my education prepared me to do research and those skills carry over into any subject. I finally bought these, which are reading glasses.

    The only result I noticed was that my eyes no longer teared up and felt strained on awakening, a significant change. I know some people are much more restive to screens and might find these of benefit.
    If you don’t need reading glasses there are the non-readers, the best make of which may be made by Gunnar. Reading the reviews of those glasses you see that some people have very bad reactions to screens and the glasses help.
    I believe these problems have not been reported with ereaders.
    To my knowledge this is not related to the blue light, melatonin ,sleep disorder issue.

  11. New! Fire HD 8 Reader’s Edition (available for pre-order) | I Love My Kindle Says:

    […] Scientific study compares bedtime reading risk from iPad, iPhone, PW1 […]

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