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Study: e-books may negatively impact our sleep after reading

Posted December 30, 2014

It‘s no secret that reading is good for us. Just six minutes of reading is enough to reduce stress, slow down the heart rate and ease tension in the muscles. Scientists say that reading is not only pleasure but it has all the added benefits.

Image credit: Giuseppe Milo via Flickr, CC BY 2.0.

Image credit: Giuseppe Milo via Flickr, CC BY 2.0.

Much more enthralling than watching a movie or a TV show (although they have their own benefits as well), a good book can keep us amused while developing our life skills. Snuggling up with a good book in bed has long been seen as a way to wind down at the end of the day. However, a new study shows that people ought to give some thoughts not just to what they read but also how they read.

Planning to read in bed tonight? It may be better to read an actual book instead of an e-book reader. It doesn‘t matter how boring the text may be, because everything may depend on a single question: are you going to read it on an e-reader or not? A new study found that a bright light emitted from e-books influences our sleep quality. Besides, it can also be more difficult to fall asleep and get a good rest.

Researchers from the Harvard Medical School in Boston, USA, analysed the production of the sleep hormone melatonin in 12 participants. All participants needed to complete two reading conditions: the first one was to read an LE-eBook in otherwise very dim room light for 4 hours before bedtime for five consecutive evenings. The second task was to read a printed book in the same very dim room light for 4 hours before bedtime for five consecutive evenings. Researchers collected blood samples every hour to assess plasma melatonin concentrations; besides, they also assessed total sleep time, sleep efficiency and the time spent in each sleep stage.

After 14 days experiment, the authors of study compared the biological effects of reading an electronic book with reading a printed book before bedtime.

Experts 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 study results are of particular concern because they revealed important evidences which are linked with 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. In addition to this, researchers suggested that using e-books before bedtime can increase the risk of delayed sleep-phase disorder and sleep-onset insomnia, especially among individuals living in society who self-select their bedtimes and wake times.

Researchers noted: „Since more people are choosing electronic devices for reading, communication and entertainment – particularly children and adolescents who already experience significant sleep loss – research evaluating the long-term consequences of these devices on health and safety is urgently needed.“

Maybe it’s time to start thinking of printed and on-screen texts in another way: not as about an old technology and its inevitable replacement, but as different and complementary interfaces.

Sources: Science Daily,, American

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