Smartphones and tablets in bedrooms disrupt the sleep of children even if they are switched off, a new study has shown.

Researchers at King’s College London and Cardiff University reviewed 11 studies involving more than 125,000 children to find out if technology was impacting sleep.

They found that using smartphones or tablets before bedtime doubled the risk of a disrupted night’s sleep and raised the changes of feeling excessively sleepy the following day by two-fold.

But crucially, sleep was also significantly disturbed by the mere presence of devices – almost to the same level as actually using a gadget – suggesting that they should be removed from bedrooms altogether to improve sleep.

It is thought that the ‘always on’ nature of social media and instant messaging means children are continuously stimulated by devices in their environment, even when they are not using them.