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Reading E-Books Before Bedtime Could Interfere With Sleep

Last updated June 24, 2015

Johan Larsson

A study comparing the effects of an electronic book with conventional printed books concludes that use of light-emitting e-books before bedtime can impact sleep, circadian rhythm, and extent of alertness upon waking up.


A study comparing the effects of an electronic book with conventional printed books concludes that use of light-emitting e-books before bedtime can impact sleep, circadian rhythm, and extent of alertness upon waking up.

Artificial light has extended work hours and changed habits, altering what was “normal.” It has been known for a while that the benefits of having light even after sunset came with some disadvantages. The light from lamps is a mixture of visible, infrared, and ultraviolet (UV) emissions. Scientific research has shown that exposure to artificial light could actually increase risks of breast tumor growth, colorectal, and prostate cancers. Artificial light has been also been implicated in the risk of developing skin cancers like melanoma, squamous cell carcinoma, and basal cell carcinoma.

Increasingly, a significant source of artificial light in most households is the one emitted from electronic devices such as computers, cell phones, etc. Many electronic devices emit blue light, which has been shown to influence melatonin secretion.

With this background, the study being discussed here enrolled 12 participants to read books on light-emitting iPads for 4 hours before bedtime for five nights at a stretch. The same experiment was also done with printed books. The order was scrambled, with some participants reading the e-book first while others followed the reverse order.

The results showed that, compared to printed book readers, iPad readers:

  • Took longer to sleep.
  • Felt less sleepy in the evenings.
  • Were more sleepy in the mornings after eight hours of sleep.
  • Reported being less alert in the mornings after eight hours of sleep.
  • Spent less time in REM sleep.
  • Showed reduced secretion of melatonin (melatonin is a hormone that plays a role in inducing sleepiness).
  • Had a circadian rhythm delay of one hour (assessed by melatonin levels).

Although this study was conducted using iPads, the results were also applicable to other blue light emitting sources like e-readers, cell phones, laptop computers, LED monitors, etc.

One of the researchers and authors of the study, Dr. Charles Czeisler of the Brigham and Women’s Hospital (BWH), says in the BWH Press Release, “In the past 50 years, there has been a decline in average sleep duration and quality.” He continues, “Since more people are choosing electronic devices for reading, communication and entertainment, particularly children and adolescents who already experience significant sleep loss, epidemiological research evaluating the long-term consequences of these devices on health and safety is urgently needed.”                        

Since electronic devices are here to stay, what could one potentially do to minimize harm? According to Harvard Health Publications, the following tips could help:

  • Exposure to bright sunlight during the day, which will improve alertness and reduce sleepiness.
  • Bright sunlight also has the ability to boost sleep.
  • If a night light is needed, use of red night light, which reportedly has the least effect on circadian rhythms.
  • Shutting off electronic devices a few hours before sleep.
  • Wearing blue light-blocking glasses if one has to work at night.

In other words, a few common-sense steps could help an individual sleep well, stay alert, and keep healthy.

Written by Mangala Sarkar Ph.D.

References and Information Sources used for the Article:


Reviewed and Approved by a member of the DoveMed Editorial Board
First uploaded: June 24, 2015
Last updated: June 24, 2015