While it is widely accepted that screen time before bed affects sleep quality, a new analysis of more than 122,000 people has found exactly how much impact these behaviours have.
Those who used phones, tablets or laptops before going to bed each day got 48 minutes less sleep per week.
The study also revealed that the regular device users were also more likely to go to bed later.
The researchers, led by experts from the American Cancer Society, gathered data on adults from the US and Puerto Rico, including their sleeping habits and screen use − not including television − in the hour before sleep.
Man checking his smartphone. Photo: Getty Images
Man checking his smartphone. Photo: Getty Images
Today's News in 90 seconds - 28th March 2025
Some 41pc of the participants used a screen before bed every single day, while 17pc reported no screen use before bed.
Those who used their phones before bed every day were 33pc more likely to complain of a bad night’s sleep than those who did not use a screen in the hour before bed.
The group was split into morning larks and night owls, referring to those who prefer to be active earlier in the day or later at night, with the former accounting for 58pc of the group.
This can lead to reduced sleepiness and increased alertness
The team found that morning larks who used a screen before bed went to sleep 9.33 minutes later on workdays compared with those who kept screens out of the bedroom.
And night owls went to bed 15.62 minutes later on workdays. Results were similar for non-workdays.
The light from the screens may play a part, the authors suggested.
“Light exposure at night can disrupt sleep by disrupting this natural cycle through delaying the onset of melatonin,” they wrote. “This can lead to reduced sleepiness and increased alertness.”
But they said that disruptions to sleep due to screen use “may not be limited to effects of screen light,” adding: “It is not only the light being emitted from these devices that needs to be considered, but the content as well.”
They said that social media is one of the major sources of content being consumed on mobile devices but “only a handful of studies have looked at social media use at bedtime”.