If your morning routine currently includes trying to rouse a sleepy teen from their bed, then you're not alone. A new study has shown that today's adolescents are clocking fewer hours of sleep than previous generations - and smartphones are to blame.
The research, published in the journal Sleep Medicine, examined data from two large surveys of sleep duration, the first conducted in 1991, to determine whether the self-reported hours of sleep in US teens changed between 2009 and 2015. More than 360,000 adolescents were included in the final analysis
Compared to 2009, teens in 2015 were 16 - 17 per cent more likely to report sleeping fewer than seven hours a night, on most nights of the week.(Experts believe teens need approximately nine hours' sleep per night for optimal functioning.)
"New media screen time (electronic device use, social media, and reading news online) increased over this time period," the authors write, "and was associated with increased odds of short sleep duration."
The researchers also found what they called a clear "exposure-response" relationship for electronic devices after two or more hours of use per day. In other words, the more hours spent on Facebook, Snapchat, or Instagram, the more sleep-deprived the teen. Specifically, researchers found that teens who spent five hours a day online were 50 per cent more likely to not sleep enough than their peers whose use was limited to only one hour per day.
But, according to the researchers, it's not as simple as teens choosing scrolling over sleep. Prior research has indicated that light wavelengths emitted by smartphones and tablets can interfere with the body's natural sleep-wake rhythm.
Interestingly, other activities previously linked to not clocking as much shut-eye (homework, paid work, and watching television) were actually relatively stable or even decreased between 2009 - 2015, "making it unlikely they caused the sudden increase in short sleep duration".
"Teens' sleep began to shorten just as the majority started using smartphones," said study co-author Jean Twenge, who also authored iGen: Why Today's Super-Connected Kids Are Growing Up Less Rebellious, More Tolerant, Less Happy -- And Completely Unprepared for Adulthood. "It's a very suspicious pattern." In fact, foregoing sleep for social media or texting friends has even been given its own term: "Vamping", with a 2014 study showing that at least 80 per cent of teens had been smartphone vampires at some stage during high school.
Co-author Zlatan Krizan explains that in order to make up for all those lost Zs, teens will chase sleep at other times. "Our body is going to try to meet its sleep needs, which means sleep is going to interfere or shove its nose in other spheres of our lives," he said. "Teens may catch up with naps on the weekend or they may start falling asleep at school."
Acknowledging that smartphones and other tablets are an "indispensable" part of modern life, Twenge notes that the key is moderation - and limiting use to two hours per day. It's advice parents should be taking on board for themselves, too.
"Given the importance of sleep for both physical and mental health, both teens and adults should consider whether their smartphone use is interfering with their sleep," she says. "It's particularly important not to use screen devices right before bed, as they might interfere with falling asleep."
The findings follow recent research released by Telstra, which showed that Australian kids are spending, on average, an entire day per week on their smartphones. More than two thirds of children aged three to 17 own a smartphone, with kids spending 21 hours and 48 minutes per week glued to their devices.
So what can parents do?
In new guidelines released last year, The American Academy of Pediatrics reiterated the importance of ensuring that teens' media use doesn't "take the place of adequate sleep, physical activity and other behaviours essential to health."
To manage these competing priorities, the AAP recommends parents:
- Promote that children and adolescents get the recommended amount of daily physical activity (1 hour) and adequate sleep (8–12 hours, depending on age).
- Ensure children do not sleep with devices in their bedrooms, including TVs, computers, and smartphones.
- Avoid exposure to devices or screens for one hour before bedtime.
- Create a personalised Family Media Use Plan tool.