Reading from an iPad or from a book in bed: the impact on human sleep. A randomized controlled crossover trial

Objective: To objectively and subjectively compare whether reading a story for 30 min from an iPad or from a book in bed prior to sleep will differentially affect sleep. Methods: Sixteen students (12 females, mean age 25.1 +/- 2.9 years) underwent ambulatory (sleeping in their own beds at home) polysomnographic (PSG) recordings in a counterbalanced crossover design consisting of three PSG nights (one adaptation night, two test nights) and two different reading materials: read from an iPad or from a book. Illumination was measured during reading and Karolinska Sleepiness Scale was completed prior to turning the light off. Sleep diaries were kept to assess subjective sleep parameters from day to day. Results: Illumination was higher in the iPad condition compared to the book condition (58.3 +/- 6.9 vs 26.7 +/- 8.0 lux, p < 0.001). Reading a story from an iPad decreased subjective sleepiness, delayed the EEG dynamics of slow wave activity by approximately 30 min, and reduced slow wave activity after sleep onset compared to reading from a book. No parameters of sleep state timing and sleep onset latency differed between the two reading conditions. Conclusion: Although there was no direct effect on time spent in different sleep states and self-reported sleep onset latency, the use of an iPad which emits blue enriched light impinges acutely on sleepiness and EEG characteristics of sleep pressure. Hence, the use of commercially available tablets may have consequences in terms of alertness, circadian physiology, and sleep. Published by Elsevier B.V.