There’s an old saying in sleep medicine: bedrooms are for slumber, sex and nothing else. Nowadays, though, that idea is all but obsolete — thanks to the all-invading domination of smartphones, tablets and laptops.
Yet a wealth of research demonstrates why everyone should banish screens from the bedroom — even if they’re switched off. And it’s not just because of the light they generate.
Experts fear the havoc they wreak on our sleep is sentencing us — and our children — to lives dogged by obesity, diabetes and even Alzheimer’s.
The Mail reported on the latest evidence, with NHS data showing that in the past decade, hospital attendances in England for children under 14 with sleep disorders have tripled.
And it’s their use of mobile technology that is being blamed. Phone and tablet screens are now a mainstay of teenagers’ bedrooms. Studies show that seven in ten British children and nine in ten teenagers have at least one device in their bedrooms.
Almost half of teenaged schoolchildren check their mobile phones after they have gone to bed, according to a survey undertaken by educational organisation the Headmasters’ and Headmistresses’ Conference.
The blue light that electronic screens emit is a major source of insomnia and sleep problems.
Numerous studies, such as a report in the journal Current Biology in 2013, warn that the blue wavelength suppresses production of the sleep-inducing brain chemical, melatonin — making it harder to fall asleep and to enjoy good quality sleep.
The thrill of social media also puts a stop to unbroken slumber. "Children are taking electronic devices to bed and continuing to use them through the night," Dr Simon Archer, a reader in sleep genetics at the University of Surrey, told Good Health.
"The excitement of rapid communication has a stimulating effect that prevents sound sleep."
A sense of unprecedented excitement may explain why the mere presence of screens in bedrooms — even if smartphones and tablets are switched off — disrupts children’s sleep.
This was the finding of a study of 125 000 children by researchers at King’s College London, published in the medical journal JAMA Pediatrics last November. Dr Archer warns: "If children grow up with a lifetime of sleep disruption, then there is an increased risk of weight-related problems such as diabetes."
A report from 2014 in the Canadian Journal of Public Health found that the more screens children aged nine to 11 had in their bedrooms, the more likely they were to be both sleep-deprived and overweight.
Poor sleep is thought to upset the balance of appetite-controlling hormones such as ghrelin, which tells our brains when we are hungry. When tired, we are more prone to crave foods high in sugar and fat.
Dr Archer fears that lack of sleep may severely harm teens’ — and adults’ — brains in later life.
"The risk of cognitive disorders such as Alzheimer’s may be increased," he says. "Research on this is in its early days, but the danger is there."
Dr Guy Meadows, clinical director of the Sleep School in London, is particularly worried by the effect of screen-induced insomnia on intelligence.
"Our brains are still forming right up to the age of 21," he says. "Most of the development occurs when we are sleeping. If this is not allowed to happen, we see children developing attention issues and hyperactivity, challenging behaviour and poor memory."
It is not just children who are affected by tech in bedrooms. Adults run similar health risks. Even a Kindle in the bedroom can cause insomnia, thanks to the light it emits, according to a 2015 study in the Proceedings of the National Academy of Sciences.
Relationships suffer, as well.Research by Relate in 2011 found that couples were spending more time looking at their laptops than they were looking at each other.
Sleep doctor Guy Meadows long ago banished all mobile devices from his bedroom. "Years ago, I found myself checking Facebook in bed and thought it ridiculous," he says. "I realised I needed to give my brain respite in order to relax and go to sleep."
But many parents fear that banning children from having mobile devices in their bedrooms makes them look like killjoys.
Dr Neil Stanley, former chair of the British Sleep Society, has a robust answer: "Our parents had no problem with being miserable old gits. We have to stop being scared to tell children that these technologies can be bad for them."