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| E-readers 'damage sleep and health,' doctors warn | E-readers 'damage sleep and health,' doctors warn |
| (about 7 hours later) | |
| 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. | 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 an e-reader, which led to poorer quality sleep and being more tired the next morning. | They found it took longer to nod off with an e-reader, which led to poorer quality sleep and being more tired the next morning. |
| Experts said people should minimise light-exposure in the evening. | 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. | 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. | But there has been growing concern about the dangers of light before bedtime. |
| Body clock | Body clock |
| 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. | 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. | 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. | 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. | 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. | 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. | 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 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. | The findings were published in the journal Proceedings of the National Academy of Sciences. |
| 'Concern' | 'Concern' |
| 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." | 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. | He said 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. | "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." | "Thus, the melatonin suppression that we saw in this study among participants when they were reading from the light-emitting e-reader concerns us." |
| Sleep hygiene | Sleep hygiene |
| Dr Victoria Revell, who researches the impact of light on the body at the University of Surrey, told the BBC: "This is a very good study and I think it's really interesting. | Dr Victoria Revell, who researches the impact of light on the body at the University of Surrey, told the BBC: "This is a very good study and I think it's really interesting. |
| "We should be advising people to minimise their [light-emitting e-reader] use in the evening, particularly teenagers who are a group that are using their phones and tablets late in to the evening." | "We should be advising people to minimise their [light-emitting e-reader] use in the evening, particularly teenagers who are a group that are using their phones and tablets late in to the evening." |
| Teenagers naturally have a late body clock, which makes them slow to rise in the morning and up late at night. | Teenagers naturally have a late body clock, which makes them slow to rise in the morning and up late at night. |
| "People who already have a delayed body clock are delaying themselves much further and that is a very important message," Dr Revell added. | "People who already have a delayed body clock are delaying themselves much further and that is a very important message," Dr Revell added. |
| Prof Czeisler agreed, saying there was "special concern" for teenagers who were already sleep deficient by being forced to get up early for school. | Prof Czeisler agreed, saying there was "special concern" for teenagers who were already sleep deficient by being forced to get up early for school. |