E-books impair sleep patterns

E-books impair sleep patterns

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A higher proportion of blue light reduces the release of the sleep hormone melatonin

Reading brightly lit tablets can negatively affect sleep. According to a study, "four hours of reading can result in a 1.5 hour shift in the sleep-wake cycle". This is reported in the latest issue of the journal Proceedings of the United States Academy of Sciences (PNAS). "The high proportion of blue light is suspected" as a trigger.

Comparative test with conventional books "The use of electronic devices for reading, communication and entertainment has increased significantly in recent years," write the researchers led by Anne-Marie Chang from Harvard Medical School in Boston. So they wanted to see how this trend affects sleep. To investigate this, they had twelve young women and men read tablets and books for five days in a controlled period before going to bed and then compared the results.

Melatonin release shifts The measurements showed that the subjects who read from tablets fell asleep about 10 minutes later on average, that the REM phases were shortened by twelve minutes each and that the subjects were not as fit in the morning as the subjects the control group.

The effects were most clearly evident from the melatonin level, which dropped by 55 percent. As a result, the sleep-wake rhythm of the tablet group shifted by about 1.5 hours compared to the group with conventional reading. They were significantly more awake than the "bookworms" at 10 p.m. at bedtime.

Blue light presumed to be the cause To explain the causes, the scientists around Chang referred to older studies that blame high levels of blue light, such as that found in television sets, computer monitors and tablets.

However, the study did not examine the effects of e-books separately. As the Washington Post announced, the manufacturers of such e-books, such as Kindle or Amazon, assured that their products use other light sources and would therefore be significantly easier on the eyes.

Increased cancer risk Regarding the health effects, the researchers around Chang said that the study was particularly important “because it was already identified in studies on shift work and recognized as a carcinogen by the WHO, triggered and increased by the impairment of the melatonin level by exposure to night light Risk of colorectal cancer, prostate cancer and breast cancer ”… confirm. "Our results show that the electrical light we are exposed to between sunset and bedtime has profound biological effects," the researchers write. However, they limited the results of their study to the effect that the tablets were as bright as possible, while the light would have been dimmed when reading a book. (jp)

Image: Cristine Lietz / pixelio.de

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