It might be time to change your bedtime reading habits.

By Liz Steelman
Updated March 14, 2016
Tim Platt / Getty Images

Do you feel sleep deprived, even if you’re clocking in eight hours of shuteye a night? Well, if your bedtime routine involves reading on your iPad before turning off the lights, a simple switch to a physical book could help you feel more well-rested. According to a new study from the University of Bergen in Norway, reading from a tablet alters sleep quality compared to reading from a physical book.

For the study, published in Sleep Medicine, participants first kept a regular sleep-wake schedule for a week before data was collected. The following week, researchers began to record data about their sleep, including brain activity, sleep time, and sleep efficiency—with the participants sleeping in their own beds for the duration of the study. For the first night, they had participants continue their regular sleep patterns. On the next night, participants were instructed to read from an iPad for half an hour in bed before turning off the light and going to sleep. For the last night, they read for 30 minutes—but this time with a paper book and using the lights in their bedrooms.

Researchers expected the high levels of blue light emitted from the iPad would make it harder for participants to fall asleep compared to reading a physical book. But they found that there was no difference in how long it took to fall asleep or for how long they slept. All participants, after reading, slept the same: a little less than 8 hours total.

What was different? How sleepy participants felt before falling asleep and how the brain reacted while sleeping. After reading on an iPad, participants felt more alert than when they read a physical book. They spent less time in deep sleep, which is an important part of overall brain functioning and restoration, according to the slow brain wave activity measurements. Participants also entered the deep sleep stage about 30 minutes later, too.

An iPad isn't the only thing that might be fueling your yawns throughout the day. Take a look at other parts of your nightly routine that might be sabotaging your sleep.