According to Live Trading News, people who read from the iPad 30 minutes before they go to sleep felt less sleepy after the device was turned off than those who turned the pages of a paper book. Researchers are chalking this up to electrical activity in the brain, as the blue light emitted from electronic devices affects use in a different way than a reading light.
"Since light has an alerting effect, we predicted a lower sleepiness in the iPad condition at bedtime compared to the book condition," said Jane Gronli, the lead author of the study conducted at the University of Bergen in Norway. "We found a delay of 30 mins in the generation of the restorative slow waves during sleep in the iPad condition."
Gronli and her fellow researchers focused their study on 16 participants ages 22-33 who did not smoke. None of them had any mental health or sleeping problems, and all were familiar with tablets. For three nights polysomnographic recordings were taken during sleeping hours; one night without any sort of activity before bed, one night after reading a paper book, and one night after reading from a tablet.
While the time it took to fall asleep and the time spent asleep were similar, the researchers noted that on the night participants read from the paper book they felt sleepier after putting the book down. Along with the reports from the participants the EEG readings displayed a reduction in slow wave activity, which represents deep sleep.
The light from the tablet reduced slow wave activity by tricking the brain into thinking it was daytime, triggering awake parts of the brain that control alertness.
"Slow wave sleep EEG activity is important for the restorative effect of our sleep," said Gronli. Another important factor was that the experiment was conducted over three days with only one night to analyze the effects of tablets.
"We only examined one night using an iPad," said Gronli. "It is tempting to speculate that daily use of an iPad, and other blue light emitting electronic devices, before bedtime may have consequences for human sleep and cognitive performance."