They take nearly ten minutes longer to fall asleep after using their devices, compared with those reading a printed book, and their sleep is far worse. The researchers found they have less rapid eye movement, a stage of sleep thought to be crucial because it is when people consolidate memories.
The blue light powering many of our devices including phones, tables and laptops are so bright they can damage your eyes.
Many of the displays we all use today use blue light frequencies of between 415 and 455 nanometers. Tests have shown that such light can kill cells in our retinas causing damage to our sight.
It is also believed that the blue lights affect our circadian rhythm - or body clock, the 24-hour biological cycle governing our sleep and waking patterns.
Display manufacturers have decided to turn this into a marketing opportunity, so we can expect gadgets to start selling with 'safe screens'.
The new safe screens are said to work by emitting less light from the violet end of the blue spectrum, the most harmful part.
The screens feature in products exhibited by several companies at the IFA consumer electronics show in Berlin this week, reports the Daily Mail.
Scientists at Penn State and Harvard universities in the US recently found that those who regularly use e-readers before bed do not sleep for as long.
Nearly all living things have a body clock that synchronises to the 24-hour pattern of the Earth's rotation. The circadian rhythm, which also determines if we are a 'morning' or an 'evening' person, is regulated by the senses, most importantly the way the eye perceives light and dark.
Blue light, which is emitted by the low-energy light-emitting diodes used in smartphones, tablet computers and laptops, is known to be particularly disruptive to sleep.