E-books 'damage sleep and health,' say doctors
If you curl up under the duvet with an e-book for a bedtime read then
you are damaging your sleep and maybe your health, US doctors have
warned.A team from Harvard Medical School compared reading paper books
and light-emitting e-readers before sleep.
They found it took longer to nod off with a back-lit e-reader, which
led to poorer quality sleep and being more tired the next
morning.Original Kindle readers do not emit light so should be fine, say
experts.Experts said people should minimise light-exposure in the
evening. Whether you are perusing the Man Booker shortlist or leafing
through Zoella, the impact of reading on your sleep is probably the last
thing on your mind.But there has been growing concern about the dangers
of light before bedtime.
Our bodies are kept in tune with the rhythm of day and night by an
internal body clock, which uses light to tell the time.But blue light,
the wavelength common in smartphones, tablets and LED lighting, is able
to disrupt the body clock.
Blue light in the evening can slow or prevent the production of the
sleep hormone melatonin.Twelve people were locked in a sleep laboratory
for two weeks
They spent five days reading from a paperback and five days from an
iPad.Regular blood samples showed the production of the sleep hormone
melatonin was reduced by reading an e-book.
People also took longer to fall asleep, had less deep sleep and were
more tired the next morning.The researchers said other e-readers such as
the Nook and Kindle Fire produced similar wavelengths of light and would
have the same impact.
The findings were published in the journal Proceedings of the
National Academy of Sciences.Lead researcher Prof Charles Czeisler told
the BBC News website:
"The light emitted by most e-readers is shining directly into the
eyes of the reader, whereas from a printed book or the original Kindle,
the reader is only exposed to reflected light from the pages of the
book."He said disrupting sleep in turn affected health.