Yet another study demonstrated the difference between reading from a physical book and an iPad — and how it can affect the quality of one’s sleep.
While the time it took to fall asleep and sleep time remained similar under the two conditions, individuals who read from a tablet for half an hour prior to bedtime felt less sleepy and had altered electrical function in the brain during slumber, compared to those who read from a printed book.
Surprisingly, the iPad light did not delay the initiation of sleep despite the authors’ prediction of lower sleepiness due to the light’s alerting effect, said Janne Gronli, lead study author and professor at Norway’s University of Bergen.
However, there was some other function change detected.
“We found a delay of 30 minutes in the generation of the restorative slow waves during sleep in the iPad condition,” says Gronli in a Reuters report. Slow waves represent deep sleep.
The researchers analyzed data on 16 non-smokers between ages 22 and 33, who used tablets and logged no sleep, psychiatric, or medical issues. A week prior to the study, they were told to have a regular sleeping and waking routine, staying in bed as long as they needed sleep.
During the research, the subjects slept in their own beds while the scientists took polysomnographic records for three sleep nights: a night for collecting information on how much sleep each person had, another for reading from the iPad for half an hour before sleep, and another reading from an actual book for 30 minutes as well.
The EEG readings and other recordings covered data on factors such as total time asleep and efficiency of sleep, and other aspects such as time between onset of sleep and first REM sleep period.
The subjects reported feeling sleepier when they read the physical book. In contrast, they had reduced and delayed slow wave activity in the brain after reading from their tablet.
Based on measurements, too, illumination was around twice as high while one reads from the tablet versus the book, with the former emitting a high rate of blue light. Our eyes absorb blue light that tells the brain that it is daytime, triggering the wakefulness and alerting regions of the brain.
Gronli raised concerns over the findings, as slow wave sleep is crucial to attain sleep’s restorative effect. When the brain generates these waves properly during sleep, memory and cognition are enhanced, she explained.
Blue light from smartphones, tablets, and other electronic devices have been implicated in sleep problems. Gronli recommends keeping the bedroom exclusively for sleeping in, not for doing work or being on one’s social networks.
An earlier study pinpointed diet’s influence on sleep. It found that a diet containing less fiber and more sugar and saturated fat led to disrupted, less restorative sleep. High-fiber intake, on the other hand, resulted in deeper, slow-wave sleep.
Sleep is believed to affect the onset of chronic disease, including hypertension and diabetes.
Photo: Morten Oddvik | Flickr