People who read from an iPad for 30 minutes before going to sleep felt less sleepy and had different electrical activity in the brain during sleep than those who read from a physical book, a recent study found.
But the time it took to fall asleep and time spent sleeping were similar under both conditions.
“Since light has an alerting effect, we predicted a lower sleepiness in the iPad condition at bedtime compared to the book condition,” said lead author Janne Gronli of the University of Bergen in Norway. But it was surprising that the iPad light did not delay sleep initiation, she said.
However, “we found a delay of 30 minutes in the generation of the restorative slow waves during sleep in the iPad condition,” Gronli told Reuters Health by email.
The study included 16 nonsmokers’ ages 22 to 33 who were familiar with tablets and had no sleep, medical or psychiatric disorders. For a week before the study began, they were instructed to keep to a regular sleep-wake schedule and to stay in bed at least as long as they needed to sleep.
During the study, in which participants slept in their own beds, the researchers took polysomnographic recordings for three nights of sleep: one to collect a baseline of how each person slept, one night of reading from an iPad for 30 minutes before turning out the light and one night of reading from a book for the same amount of time.
On the night they read from a book, the participants used ordinary reading light in their bedrooms.
The polysomnographic recordings, including electroencephalograms to measure brain electrical activity, collected data on total sleep time, sleep efficiency, percentage of time spent in each sleep stage, and other aspects of sleep quality during the time between lights off and sleep onset as well as the time between sleep onset and first period of REM (rapid eye movement) sleep.