Click to enlarge blue light alarm. E-Books save the bedside lamp, but awake at night. – Photo: Dash Fotolia The reading on brightly lit e-book devices before bedtime can affect sleep-wake cycle. With four hours of reading time, the internal clock to unlock averaged 1.5 hours delayed sleep mode, researchers report in the journal “PNAS”. As a measure was the level of the hormone melatonin, which regulates sleep. We can assume is that the high proportion of blue light screens triggers the change.
“The use of electronic devices for reading, communication and entertainment has increased greatly in recent years,” writes the research team led by Anne -Marie Chang from Harvard Medical School in Boston.
They examined the impact of e-book reader on the sofa by twelve healthy young men and women before bedtime five evenings in a row both e-books and books were read. The subjects read each four hours before 22 clock the light was deleted. At six clock in the morning they were awakened again.
subjects felt the morning matt
The measurements showed medical values that the subjects fell asleep about ten minutes later, according to the e-book reading as after reading the printed edition. The dream phase (REM sleep) were shortened at the e-book reading to almost twelve minutes and the subjects felt the morning much duller and less recovery than those who read traditional books.
The biggest impact had the e-book reading up on the sleep hormone melatonin: its distribution was reduced by 55 percent. On the fifth night of the e-book reading was the melatonin curve indicating the sleep-wake cycle, shifted by 1.5 hours compared to the evenings with printed reading backwards. To set bedtime by 22 clock e-book readers were so much more alert
Blue light wakes
Chang and colleagues refer to other studies that have shown that short-wave. – So blue – light on people like an alarm am working. The body then suppress the fatigue due to the reduced secretion of the sleep hormone melatonin. Many electronic devices such as televisions, computers and e-book readers, the proportion of blue light is particularly high. Questionable that was mainly because a decreased melatonin production can also increase the risk for cancers of the colon, breast and prostate. “Our results show that the electric light, which we are exposed between dusk and bedtime, profound biological effects has” the researchers write. However, the conditions of the two readings of the experiment have differed greatly: While e-books were set maximum light, the books were read in dim light. (AP)
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