"Teenagers sleep less when they have more computer screen time, says study,” The Guardian reports.
The study involved almost 10,000 older teens in Norway and included any device that had a screen, such as tablets, laptops, games consoles, smartphones, PCs and TVs. It found that those who used electronic devices in the hour before going to bed took longer to fall asleep. They were also more likely to feel they needed at least another two hours sleep more than they actually got. The same was true of those who spent at least two hours of their leisure in various forms of screen time. The more time a teenager spent on electronic devices, the less sleep they tended to get.
It's important to note that the researchers did not assess whether any of the differences seen had any impact on the teens' daily lives or health. Also, the study design means that we cannot interpret this as saying that device usage directly causes lack of sleep, as they were both measured at the same time. In some cases, teenagers unable to sleep may have used a device out of boredom.
However, it is important to stress that getting enough sleep is important for all age groups.
Where did the story come from?
The study was carried out by researchers from Uni Research Health and other research centres in Norway. It was funded by Uni Research Health and the Norwegian Directorate for Health and Social Affairs.
While the UK media reported the findings of the study accurately, they did not mention that this type of study cannot identify cause and effect.
The suggestion by some sources that restricting screen time in the evening would improve sleep also cannot be proven by this study. However, reducing activities that might replace or distract from sleep may improve sleep patterns.
What kind of research was this?
This was a cross-sectional study looking at whether there was a relationship between the amount of time that adolescents spend using electronic devices and how much sleep they get.
The researchers say that electronic devices have been used much more in the past decade, including by teens. This could be one factor contributing to the “shift towards poorer sleep” in adolescents seen over the same period. Several studies have found that more device usage is linked to less sleep. This body of research mainly focused on one or two devices (often TV and computers), and it has been suggested that more research is needed on newer devices and assessing different measures of sleep and sleep problems.
While the study design can tell us whether certain characteristics tend to occur together (e.g. more screen time and less sleep), it cannot tell us if one causes the other. The study also cannot tell us how these characteristics have changed over time.
What did the research involve?
The researchers assessed electronic device use, as well as sleep, in 9,843 adolescents aged 16 to 19 years old. They analysed whether those who used screens or electronic devices more tended to sleep different amounts to those who used them less.
The adolescents all lived in one county in Norway (Hordaland) and were taking part in the youth@hordaland study. This study invited all adolescents born from 1993 to 1995, and all students attending secondary school in 2012 in Hordaland to participate. Looking at devices and sleep was not the main aim of the study, which focused on mental health problems. Teens who agreed to participate (53% of those asked) were sent a web-based questionnaire to fill out.
The teens were asked about their use of six different electronic media devices and whether they used them in the bedroom during the hour before they went to sleep. The devices were:
- Cell phone
- MP3 player
- Games console
They were also asked how much time they spent on various on-screen activities outside of school hours on weekdays.
The teens were also asked:
- their typical bedtimes and getting up times in the week and on weekends
- how long it took them to fall asleep once in bed
- how much time they spent awake due to waking up in the night
- how much sleep they needed to feel rested
The researchers used this information to find out how much “sleep deficit” the teens had by subtracting how much sleep they actually reported having from how much they said they needed.
They looked at the difference in sleep among those using devices for different amounts of time.
What were the basic results?
The researchers found that most of the teens used electronic devices in the hour before going to sleep – between about 30% and 90%, depending on the device. Boys spent about six-and-a-half hours on leisure “screen time” on weekdays, and girls spent about five-and-a-half hours.
Using any electronic device in the hour before sleep was associated with an increased likelihood of taking more than an hour to fall asleep once in bed and also with needing at least two hours more sleep than they actually had. The same was true of any leisure screen time activity of over two hours.
The more time a teen spent on electronic devices, the less sleep they tended to get. In addition, those who used multiple devices also tended to be more likely to take at least an hour to fall asleep than those using just one device.
They found no differences between boys and girls in their analyses of the relationship between devices and sleep.
How did the researchers interpret the results?
The researchers conclude that adolescents frequently use electronic devices during the day and at bedtime. Those who used these devices more tended to sleep less. They say this suggests that “recommendations on healthy media use could include restrictions on electronic devices”.
This large cross-sectional study found that older teens who use their electronic devices more tend to sleep less.
The findings are unlikely to come as much of a surprise and it supports findings from previous studies on “screen time”. The new aspect of this research is that it has studied newer devices such as tablets, MP3 devices and phones, as well as PCs and TV. All of them seemed to have similar associations with sleep. The researchers say they did not assess why the teens were using the devices – for example, whether they were doing homework. They also note that some of the differences seen were small, and they did not assess whether they had any impact on the teens’ daily lives or health.
However, the study design means that we cannot interpret this as saying that device usage directly causes lack of sleep, as they were both measured at the same time. It is also possible that teens who cannot sleep use the devices to entertain themselves.
Another limitation is that the study did not take into account any other characteristics of the teens in their analyses. They also only used the teens’ own reports of their sleep patterns.
Overall, the practical implications of the study are probably limited. However, getting enough sleep is important for all age groups. Read more information and advice about children and sleep.
Analysis by Bazian
Edited by NHS Website
Links to the headlines
The Guardian, 3 February 2015
The Daily Telegraph, 2 February 2015
The Independent, 3 February 2015
Mail Online, 3 February 2015
Daily Express, 3 February 2015
Links to the science
BMJ Open. Published online February 2 2015