eReaders and Circadian Rhythms

An interesting study about the effects eReaders have on people. The full PDF is free. PR


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.

11 Replies

  • f.lux set at 1200K (ember) helps a lot if someone is supersensitive to blue light. Even 3400K is fine. (Of course that's just for the computer screen.)

  • It delays sleep by 10 minutes. IF melatonin is affected..take a tad amount of it by tablet. The snooze alarm is your real true enemy. True that if you are waiting for a certain email or response of some kind that you will be alert, more likely to drift off and then come to so you can check the email.. best to just say that after 9pm I don't respond to emails until the next day. Sleep is precious. Better to turn on soft music to relax and sleep with.

  • And what about TV?

  • I don't think people generally sit close enough to a TV for it to be a problem. Although I would suspect the problem would be increased if watching it in a darkened room (do people still do that?).

    My Kindle is one of the old ones. It doesn't really emit light - ie you have to have the light on to read it. Yet I have noticed recently that I'm not sleeping well or quickly again :-( I wonder if this is the culprit?

  • When you go by people's places at night and they have the TV on, the room light looks blue. Blue keeps a person awake. Orange (like sunset) helps to stimulate melatonin production.

    There was a study done recently using sour cherry juice because it contains melatonin. It helps a bit for people to get to sleep faster and stay asleep longer. 1 ounce before bedtime and another ounce if a person wakes up during the night. (good luck with the sugar content though...) I bought frozen pitted sour cherries for a recipe this Christmas. No sugar added.......... SOUR! Phew.

  • Thanks for link PR4NOW. I know someone to whom I shall pass on the link.

  • but I love reading my E reader before I drift off, it makes me sleepy.

  • I have found also that using my i phone too much makes my hands hurt (painful tingling) as well!!

  • It should be noted that most dedicated eBook readers are not actually light emitting.

    Most, if not all, ebook readers use e-ink and do not emit light.

    The Kindle Paperwhite readers are front-lit, with the light being directed backwards towards the e-ink display.

    This article is a referring to light emitting devices, but slightly misleadingly refers to these as ereaders, whereas it appears to be describing the reading of books on phones and tablets, which have light emitting displays.

  • Thank you for this clarity, yousurname.

  • very interesting article Thank you for sharing

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