07/09/2012 11:03 BST | Updated 14/08/2013 11:40 BST

Reading Tablet In Bed May Cause Insomnia By Suppressing Melatonin

Exposure to back-lit electronic devices, such as tablets, before bedtime could lead to sleeplessness, suggests a new study.

A two-hour exposure to self-luminous displays may cause melatonin suppression strong enough to affect sleep by disturbing the body's natural circadian rhythm, a small new study in the journal Applied Ergonomics suggests.

“Our study shows that a two-hour exposure to light from self-luminous electronic displays can suppress melatonin by about 22%. Stimulating the human circadian system to this level may affect sleep in those using the devices prior to bedtime,” said study author Mariana Figueiro, in a statement.

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Melatonin is a hormone produced by the body when it’s dark to encourage sleepiness.

Suppression of melatonin by light has been implicated in sleep disturbances, increased risk for diabetes and obesity, as well as increased risk for more serious diseases, such as breast cancer.

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Participants in the study used self-luminous tablets to read, play games, and watch movies. While one-hour exposure to tablets caused little affect, after two hours, melatonin levels dropped significantly.


Figueiro said in a statement: “We recommended dimming these devices at night as much as possible in order to minimize melatonin suppression, and limiting the amount of time spent using these devices prior to bedtime.”