(Reuters Health) – - 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.
the time it took to fall asleep and time spent sleeping were similar under both
“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.
said they felt sleepier when reading the physical book, as reported in Sleep
Medicine. After reading from an iPad, EEG readings showed delayed and reduced
slow wave activity, representing deep sleep, in the brain after sleep onset
compared to when the participants had been reading from a book.
eye absorbs short wavelength blue light and signals to the brain that it is
daytime by triggering waking and alerting active brain areas, Gronli said.