There is a popular misconception that e readers help you sleep at night; however the fact is that the make shifts in your circadian clock affecting your sleep quality.
When someone is exposed to light in the early night time hours it reduces the production of melatonin, shifting the circadian clock making it more difficult to drift off at bedtime.
Anne-Marie Chang, assistant professor of bio-behavioural health at Penn State, said that electronic devices emit light that is a short-wavelength-enriched light; these have a higher concentration of blue light which reaches around 450mm. This differs in composition to natural light and has a greater effect on sleep and circadian rhythms.
Chang observed 12 adults over a two week period and compared their night time habits from reading a paperback to reading an I Pad. The participants’ melatonin levels, sleep, next morning alertness and other sleep related measures were all carefully monitored.
Those who read from e readers were tired and took longer to cope the next morning which impacted daytime functioning. This is much more worrying in the real word rather than just a controlled environment.
The researchers found that the iPad, iPhone, Kindle, Kindle Fire and Nook Colour all emit some degree of brightness. The Kindle E Reader does not emit light and the I Pad emits the most amount of light.
The study is published in the Proceedings of the National Academy of Science.
Tagged in Sleep