If you have trouble sleeping, laptop or tablet use at bedtime might be to blame, new research suggests. Mariana Figueiro of the Lighting Research Center at Rensselaer Polytechnic Institute and her team showed that two hours of iPad use at maximum brightness was enough to suppress people's normal nighttime release of melatonin, a key hormone in the body's clock, or circadian system. Melatonin tells your body that it is night, helping to make you sleepy. If you delay that signal, Figueiro says, you could delay sleep. Other research indicates that “if you do that chronically, for many years, it can lead to disruption of the circadian system,” sometimes with serious health consequences, she explains.

The dose of light is important, Figueiro says; the brightness and exposure time, as well as the wavelength, determine whether it affects melatonin. Light in the blue-and-white range emitted by today's tablets can do the trick—as can laptops and desktop computers, which emit even more of the disrupting light but are usually positioned farther from the eyes, which ameliorates the light's effects. The team designed light-detector goggles and had subjects wear them during late-evening tablet use. The light dose measurements from the goggles correlated with hampered melatonin production.

On the bright side, a morning shot of screen time could be used as light therapy for seasonal affective disorder and other light-based problems. Figueiro hopes manufacturers will “get creative” with tomorrow's tablets, making them more “circadian friendly,” perhaps even switching to white text on a black screen at night to minimize the light dose. Until then, do your sleep schedule a favor and turn down the brightness of your glowing screens before bed—or switch back to good old-fashioned books.

This article was originally published with the title Bright Screens Could Delay Bedtime.

7 Comments

1. 1. mhall1066 12:56 PM 2/1/13

   My wife and I, both computer programmers, noticed the correlation between evening computer user and our ability to sleep. We found a free product that automatically dims your computer screen based on time of day and time of year and location (it's smart enough to know when the sun rises/sets where you live). We've been using it for months now and have definitely noticed a difference in our ability to fall asleep. The guys that created it are giving it away - just sits in the background and handles screen brightness and color for you. There are even iPad and iPhone versions.
   
   http://stereopsis.com/flux/research.html

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2. 2. donaldjmorton 11:59 PM 2/1/13

   I wish this was a problem for me! When I take my iPad or Kindle Fire to bed to read, hoping for a nice 30-60 minutes of relaxed reading, I'm out in less than five, often not even making it a page. Consider me your outlier! :)

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3. 3. abhishekup_06 02:02 AM 2/3/13

   The article seems to be relating my situation though. I feel that now I know the cause behind my sleeplessness. However, if I paper copy of the same article instead of trying to read it in the laptop, I get asleep sooner.

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4. 4. ejbrowne in reply to mhall1066 12:35 AM 2/4/13

   Thank you for sharing the link for f.lux. I am using it right now as I am replying to you. I like how it dims the blue. My screens are still very readable.

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5. 5. Witold 08:18 AM 2/4/13

   For decades, our TV screens have been causing a similar disturbance, only milder. Probably, it all started on a massive scale with the invention of the electric bulb. Side effect of progress are often hard to predict (and harder to avoid), think about GMO, for instance.

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6. 6. sunspot 06:36 PM 2/6/13

   The author should provide a link to the study. Does the study discuss the emission spectrum of laptops modeled in this study? A 2005 study at the LRC gives the spectrum for various light sources and effects on sleep, health, etc. Also, this story was reported by Leslie Meredith at TechNewsDaily... on 9/26/12... old news.
   
   

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7. 7. bucketofsquid in reply to sunspot 05:54 PM 2/7/13

   It may be old news to you but all of the screens used in electronics today are the same as they were 2 years ago. Until enough critical mass piles up to make the manufacturers change people will continue to need to hear this. Backlit screens are implicated in depression, anxiety disorders and sleep disorders. Depression and sleep disorders are implicated in decreased immune function, obesity and heart disease. If your work tools or personal entertainment are killing you, you have the right to know.

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