If you want a decent night’s sleep stop fiddling with your phone, researchers have warned.
A US study has found that greater screen time, particularly at bedtime, is linked to disrupted sleep patterns - including taking a longer time to drop off.
“The more screen time, the worse the quality of sleep,” said Gregory Marcus, co-author of the research from the University of California, San Francisco.
The research ties in with a growing body of evidence that suggests that using electronic devices can get in the way of shut-eye.
“I think there is quite a lot of data now showing that these electronic devices being used at night is a problem,” said Simon Archer, an expert in sleep science from the University of Surrey, who was not involved in the research.
“A lot these devices emit quite a bit of blue light, and it is the blue light which is a particular problem because that suppresses the hormone melatonin,” he added. “[Melatonin] begins to rise a few hours before sleep onset and it is kind of your body’s signal to get ready for sleep.”
Blue light, said Archer, also has an alerting effect on the brain, while the perusal of content or emails that cause stress, and the act of simply using a device, could also play a role.
Published in the journal Plos One by researchers from the University of California, San Francisco and mental healthcare app Ginger.io, the study drew on self-reported answers from adults who had completed a series of online surveys as part of an international health study called Health eHeart.
Participants were also asked to download an app that continuously and automatically collected data on the number of hours during which their phone’s screen was turned on. Those who had used the app for at least 30 days were included in the team’s analysis.
In total 653 adults completed the study, with the results revealing that participants spent on average 3.7 minutes of every hour using their smartphones. Younger people and those identifying as black or “other” spent longer on average on their phones than others.
Further analysis, involving data from 136 of the participants, revealed that longer screen time was linked to fewer hours of shut-eye and a lower proportion of the time in bed spent asleep. On average, every extra minute of time individuals spent on their phone, said Marcus, was linked to a decrease in sleep duration of approximately five minutes.
The team then looked at smartphone use around bedtime for the 56 participants for whom sufficient data was available. The results reveal that greater screen time at the hour of bedtime or after was linked to a greater proportion of time spent awake in bed. What’s more, said Marcus, on average every extra minute of time individuals spent on their phone was linked to an increase in the time it took to fall asleep of a minute and a half.
The study itself does not show whether increased screen time drives poor sleep, or whether those who sleep badly end up using their phones more frequently. However, the authors referred to previous research into the disruptive effect of blue light from electronic devices, and suggest the effect of engaging websites and apps such as Facebook on sleep requires further research.
“I am a big fan of technology and think technology can help us solve many problems,” said Marcus. “However, I think that this suggests that we need to think carefully about how to optimise the use of that technology and understand the consequences of that use.”
With poor sleep linked to an increased risk of a number of health problems, from obesity to stroke, researchers say the impact of smartphones merits scrutiny.
“Although we cannot prove causality, these data do suggest that screen time, especially before bed, may be harmful in terms of helping us achieve a good night’s sleep,” said Marcus.
Archer agrees. “The whole point about sleep is [that it’s] basically downtime for the brain and the body, and revitalising and reenergising,” he said. “This type of activity just before sleep goes completely against all of that.”
