A few days ago, the BBC published an article called “Children’s screen time has little effect on sleep, says study”. If you have read any of my other articles, you’ll know that this statement contrasts with a lot of the research done to date. I thought I’d take a look at the study and break it down.
In the BBC article they interviewed the lead author who stated that he thinks it’s because many of the other studies were simply “false positives”, which means other research found something that doesn’t really exist. The author is correct that much of the other literature is flawed, I think particularly because of the study designs. And his concluding statement that we should be focusing on other factors than screens such as consistent wake times and sleep routines seems totally accurate.
However in my opinion, when I examined the study I found, rather ironically, that there are more flaws with it than a lot of other research in this area. Here’s the link to the study.
Digital Displacement Hypothesis
The study said it was examining something called the “digital displacement hypothesis”. If you haven’t heard of this before, it is the idea that by using electronics children might be foregoing other important activities important for their development such as reading, socializing, and playing sports. It’s one of the key concerns with children using screens. I don’t think the research shows either way yet, likely because screens have massive advantages for kids as well as their disadvantages.
They predicted that:
- More screen use = Less sleep duration
- More screen use = Less sleep consistency (i.e. time going to bed/waking)
- Children who use no more than 2 hours of screens per day will sleep “better” (I think they mean more sleep duration by this).
What Did They Do?
They looked at a big research database collected across the US, and analyzed data of around 50,000 people. This is obviously a huge number and gives the study lots of power. They picked 4 questions from this database and looked at how they were related to each other, controlling for a bunch of factors they could affect the findings such as age, sex, ethnicity, education levels etc.
Herein lies the problem with this research, and I’m going to try and break it down for you. The entire study is based on self-report responses….to just 4 questions….by parents….!!! Let’s take apart that sentence….
- First, the study was entirely self-report. This is common is psychological research, but for this topic it’s problematic because we know self-report is highly unreliable with sleep data, and I suspect equally so for screen use. How can someone accurately track how much phone, computer, and TV time they use each day? It’s impossible without installing some type of tracking software on multiple devices. As such, let’s make one thing clear. This study is not tracking sleep or screen use behavior at all – It’s tracking parents’ estimates of this. So instead of the misleading BBC title “Children’s screen time has little effect on sleep” it should read “Parents’ estimate of their children’s screen time is not very strongly related to parents’ estimate of their children’s sleep”. Less sexy to read, but a lot more realistic.
- Second, there were only 4 questions analyzed. All were rated on scale that had preset answers. Read each question and think critically about how inaccurate and unreliable answering them is:
- How often does your child go to bed at about the same time on weeknights?
- During the past week, how many hours of sleep did your child get on an average day?
- On an average weekday, about how much time does your child usually spend with computers, cell phones, handheld video games, and other electronic devices?
- On an average weekday, about how much time does your child usually spend in front of a TV, watching TV programs, videos, or playing video games?
- Third, the only respondents were parents. Who knows how accurate this is compared to the child’s report or to reality if it could be properly measured? I don’t know whether the parents responses tell us very much.
Also, that the author never addressed any of these problems in the article is a real problem, I don’t know why the reviewers didn’t flag these issues.
What Did They Find?
They basically found that more screen time is correlated with reduced sleep duration and more sleep inconsistency. And that kids using 2 hours of more of screens per day had shorter sleep duration and greater inconsistency. All of their hypotheses were supported.
They calculated that for every hour of screen time a child loses 3-8 minutes of sleep. And that catchy statistic is probably why this made the BBC news.
Despite this, the researchers concluded that the impact of screens of sleep time is relatively minimal, which seems fair. The 3-8 minutes for every hour of screen use is not much of an impact on sleep, really.
Because of the methodology of this study, I find I have no choice than to disregard what this study says. At least until it is supported with much more research. It could be completely true, but there are SO MANY problems in the methodology that I’m not sure anyone can take anything from this study.
As such, I don’t believe there’s a takeaway message from it. I’d look to the other literature that exists and try to understand whether there are any consistent messages coming out, and that’s what I’ve done below. Based on the research literature in general, here are my takeaways for teens:
- Screen use likely disrupts sleep, including ability to fall asleep, bedtime, and amount of time asleep.
- Screens should be turned off at least 30 minutes before bed-time.
- Don’t allow phones (and likely also laptops, tablets, computer games, TVs etc.) in their bedroom at night. Likelihood that they will wake up and use social media in the middle of the night is high.
One final comment. If you’re going to implement these ideas as parents, you should model this too. You can’t ask your kid to stop using screens before bed and not do the same!
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