MASSACHUSETTS, United States, Tuesday December 30, 2014 – If you’re planning on reading yourself to sleep with the new e-reader or tablet you got for Christmas, you may want to reconsider following warnings from American doctors that you’ll likely disrupt your sleep and damage your health.
A study conducted by a team from Harvard Medical School compared reading light-emitting e-readers and traditional paper books before sleeping.
Their findings, published in the journal Proceedings of the National Academy of Sciences, showed that it took longer to fall asleep with a back-lit e-reader, which led to poorer quality sleep and being more tired the next morning.
The only exceptions were the original Kindle readers, which do not emit light and pose no known problems.
Experts have been voicing growing concern about the dangers of light before bedtime and have recommended that exposure to light should be minimised in the evening.
That’s because our bodies are kept in tune with the rhythm of day and night by an internal body clock that uses light to gauge the time.
But blue light, the wavelength common in tablets, smartphones and LED lighting, disrupts the body clock. In the evening, it can slow or prevent the production of the sleep hormone melatonin.
For the Harvard study, 12 volunteers were locked in a sleep laboratory for two weeks. There, they spent five days reading from an iPad and five days from a paperback book.
Blood samples were tested regularly and showed that the production of the sleep hormone melatonin was diminished by reading an e-book.
Volunteers who read e-books also took longer to fall asleep, had less deep sleep and were more tired the next morning.
Other e-readers, such as the Kindle Fire and Nook, produced similar wavelengths of light and would have the same impact, the scientists said.
According to lead researcher Professor Charles Czeisler: “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.”
Professor Czeisler added that disrupting sleep in turn affected health.
“Sleep deficiency has been shown to increase the risk of cardiovascular disease, metabolic diseases like obesity and diabetes, and cancer.
“Thus, the melatonin suppression that we saw in this study among participants when they were reading from the light-emitting e-reader concerns us,” he said.