smartphone screens

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Technology firms are developing ‘safe screens’ to address fears that smartphones and tablet computers may be keeping us awake at night. Scientists say the blue light emitted by electronic devices, increasingly used by people lying in bed, could lead to interrupted sleep or even harm our eyes.

It is believed to affect our circadian rhythm, or body clock, the 24-hour biological cycle governing our sleep and waking patterns. The new ‘safe screens’ are said to work by emitting less light from the violet end of the blue spectrum, the most harmful part.

Paul Gray, an analyst at the business research firm IHS, said: ‘We’ve been told from a very early age by parents that too much screen time, in front of a TV or a computer, is bad. So a “safe” screen might resonate with consumers.’ 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. 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.

Neuroscientist Dr Anne-Marie Chang, whose research was published in the journal Proceedings of the National Academy of Sciences, said screens have an ‘extremely powerful effect’ on the body’s natural sleep pattern. ‘Our most surprising finding was that individuals using the e-reader would be more tired and take longer to become alert the next morning,’ she said. 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. The firms using ‘safe screens’ as a selling point at the Berlin show include Philips, Asus, BenQ and ViewSonic.

Stefan Sommer, of Philips, said: ‘We are shifting the harmful blue light frequencies, which are below 450 nanometers [violet] to above 460 nanometers [navy blue].’ Some researchers are sceptical about blue light fears. Serge Picaud, at the Institute of Sight in Paris, said: ‘We should not be so afraid that we bin all our screens. The light intensities produced by our screens are still relatively weak compared to sunlight.’

Vincent Gualino, a French ophthalmologist, said the real problem is not the devices but ‘over-consumption’, warning people against spending more than six hours in front of screens.