There were already suspicions that stand in front of digital screens in the evening, especially backlit, ie the most of the displays of smartphones and tablets and the new TVs, could disturb the quality of sleep. The new study takes into account specifically reading e-books on media with illuminated screen, the now very common tablet.
In the experiment some volunteers are provided to read in the new and the old style (e-books and paper books) for 4 consecutive hours for 2 weeks. The first week they read with the tablet, the second week they read normal books of paper.
It turned out that in the case of reading by electronic device, the participants had more difficulty falling asleep (an average of ten minutes longer), and reported to have no sleep. Upon awakening, by contrast, have reported feeling more tired than the nights when they had read paper books. Finally, the stages of REM sleep, the deep one, appear to have been shorter after reading from the tablet.
The final advice would be to use devices without reading backlit screen, less comfortable but more natural.