Unrestricted evening use of light-emitting tablet computers delays self-selected bedtime and disrupts circadian timing and alertness

Participants using light-emitting tablets self-selected bedtimes that were, on average, half an hour later than when reading printed materials.

• Evening use of light-emitting tablets is associated with suppressed melatonin levels compared to reading printed materials.
• The onset of melatonin secretion occurred later when participants used tablets in the evening.
• Sleep onset was also delayed when participants engaged with light-emitting devices.
• Participants reported feeling less sleepy in the evenings and experienced reduced alertness the following mornings after using tablets.

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