Evening use of light-emitting eReaders negatively affects sleep, circadian timing, and next-morning alertness

This study investigated the effects of using light-emitting eReaders versus printed books before bedtime. Participants who read eReaders took longer to fall asleep, experienced a delay in their circadian clock, and had suppressed melatonin levels. This also reduced the amount of REM sleep and left participants feeling groggier and less alert the next morning compared to reading printed books. These findings highlight the adverse impact of blue light emitted by eReaders on sleep quality, circadian rhythm alignment, and next-day cognitive performance, emphasizing the need for mindful use of electronic devices at night.

To protect sleep and cognitive health, avoid using light-emitting devices like eReaders, tablets, and smartphones for at least an hour before bedtime. Opt for printed books or devices with blue light filters to minimize melatonin suppression and circadian disruption. This recommendation is supported by strong experimental evidence showing significant sleep and alertness benefits from avoiding evening screen use.