Using e-readers at night lowers sleep quality
Using e-readers in bed at night can increase the time it takes to fall asleep and decrease the quality of sleep when it does happen, according to a study at Harvard Medical School.
Over a period of two weeks, 12 volunteers read from either an iPad or printed book for four hours before bed. The researchers then used a polygraph to measure melatonin levels, brain waves, breathing and eye movements. They also monitored how long it took for people to fall asleep and the time spent asleep. Then, they followed up with a questionnaire about sleep quality.
The scientists found that high levels of blue light emitted from e-readers reduced the melatonin sleep hormone and negatively affected morning alertness. They also concluded that the light delays the timing of REM sleep and increases the amount of time it takes for someone to fall asleep.
Although different types of e-readers were examined, researchers discovered that iPads emit the brightest light, whereas some Kindle e-readers emit no light at all, but instead reflect ambient light.
According to a recent survey, as many as nine out of 10 Americans read from an electronic screen for at least an hour before bed a few times a week. The Harvard study was published in the Proceedings of the National Academy of Sciences.