Reading from an Apple iPad or other electronic tablet before bed may make it more difficult to fall into deep, restorative sleep, according to a recent study from Norway.
Reading from a tablet also appears to make people feel less sleepy, although, surprisingly, it does not shorten the amount of time it takes to fall asleep.
The study was published earlier this month in the journal Sleep Medicine.
These findings, while not definitive, have some potentially important health implications, particularly given how ubiquitous the use of electronic devices before bedtime is. A 2011 survey by the National Sleep Foundation found that 90 to 95 percent Americans between the ages of 13 and 65 use some kind of electronic device — television, video game, cellphone or tablet — for at least one night a week in the hour or so before going to bed.
In that same poll, more than 60 percent of the respondents reported that they had a sleep problem almost every night, including feeling unrefreshed when they woke up in the morning.
The study’s design
For the current study, researchers at Norway’s University of Bergen recruited 16 people (14 women) between the ages of 22 and 33. All were healthy, familiar with using a tablet, and had no history of sleep or psychological problems. The participants were instructed to follow their normal sleep schedule for the week leading up to the study.
The study itself involved three nights of monitored sleep in the participants’ own bedrooms. The researchers used polysomography equipment to record and measure various biophysical changes — including changes in “brain waves” — that occurred in the participants while they slept.
To create a baseline of data, the participants were told on the first night to go to bed as they normally would, but without engaging in any kind of reading, whether electronic or not.
On one of the next two nights, the participants spent 30 minutes reading with an iPad before turning out the lights. On the other night, they read from a physical book, using the ordinary lighting in their room. A light meter measured the illumination at eye level on each of these nights. Those measurements revealed that the illumination was about 50 percent higher, on average, when the participants were reading from an iPad than when they were reading a hardcopy book using the lighting in their room.
An analysis of the data collected from the participants’ three nights of monitored sleep found that they reported being more alert when they turned off the lights after reading on an iPad than after reading an actual book. Interestingly — and to the surprise of the researchers — the participants did not take longer to fall asleep, however. Nor did they sleep for shorter periods of time
The researchers say the higher level of alertness is likely due to the “blue light” emitted from the iPad (and from other electronic devices, as well as from some types of lightbulbs), which tricks the brain into thinking it’s still daytime, thus delaying sleepiness.
The data also showed that once the participants were asleep, their brain waves took, on average, about 30 minutes longer to develop into slow-wave activity patterns, which are indicative of deep, restorative sleep, on the night of the iPad reading. The amplitude of the slow-wave activity was also reduced on the iPad night compared to the other two nights.
Reading on the iPad appeared to have no effect on REM, or “dream” sleep, however.
Not the last word
This study has many limitations. It involved a small group of people who were similar in age, gender and other demographics. It also observed the participants for only one night under each condition. And the only electronic reading device used was the iPad. It’s not clear if other devices, which don’t use blue light, would have similar effects on sleep. (Apple recently announced a new feature called Night Shift, which automatically reduces the amount of blue light emitted on its devices after the sun sets in the location of the device’s user.)
Still, this is not the only study that has suggested that the use of electronic devices before bed can interfere with the quality of sleep. A 2014 Harvard University study, for example, found that people who read e-books right before going to bed take longer, on average, to fall asleep (a different finding than that of the current study) and tend to awake the next morning feeling less restored than people who read “hardcopy” books.
“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,” Janne Gronli, the Norwegian study’s lead author and a sleep researcher at the University of Bergen, told Reuters reporter Kathryn Doyle.
“To avoid increased activation before bedtime the bedroom should be used to sleep in, not for work or being on social media,” she added.
FMI: You’ll find an abstract of the study on the website for the Sleep Medicine, but the full study is behind a paywall.