Climbing under the covers and reading for a while before turning out the lights is a common pastime. Also, many have found that a light, compact e-reader is easier to manage than a bulky book. However, a new study by researchers at the University of Bergen, Bergen, Norway found that individuals 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. The findings were published online on March 1 in the journal Sleep Medicine.
The goal of the study was to objectively and subjectively compare whether reading from an iPad for 30 minutes from an iPad or from a book in bed prior to sleep would affect sleep differently. The study group comprised 16 students (12 females, average age 25.1 ± 2.9 years). They underwent ambulatory (sleeping in their own beds at home) polysomnographic recordings for three nights: one adaptation night and two test nights). Two different reading materials were used: reading from an iPad or from a book. Polysomnography is an examination used to diagnose sleep disorders. It records the subject’s brain waves, oxygen level in your blood, heart rate, breathing, as well as eye and leg movements during the study. Illumination was measured during reading and Karolinska Sleepiness Scale was completed prior to turning the light off. Sleep diaries were kept to measure subjective, day to day sleep parameters. The study was a crossover design, meaning each participant underwent polysomnography after reading an iPad as well as a book.
The investigators found that illumination was higher in the iPad condition compared to the book condition (58.3±6.9 vs. 26.7±8.0 lux). Compared to reading from a book, reading a story from an iPad decreased subjective sleepiness, delayed the EEG dynamics of slow wave activity by approximately 30 minutes and reduced slow wave activity after sleep onset. No parameters of sleep state timing and sleep onset latency differed between the two reading conditions.
The authors concluded that there was no direct effect on time spent in different sleep states and self-reported sleep onset latency (time taken to fall asleep), the use of an iPad which emits blue enriched light acutely impacts sleepiness and EEG characteristics of sleep pressure. Thus, the use of commercially available tablets may have consequences in terms of alertness, circadian physiology and sleep.
This study used only one type of e-reader, an iPad, which emits blue-enriched light. Therefore, it would be of interest to conduct the study on other e-readers, such as the Amazon Kindle Paperwhite.