I’ll be the first to admit I’m occasionally guilty of checking my phone “one last time” before bed, only for 30 minutes to pass as I scroll through Facebook. Not surprisingly, kids are susceptible to the same temptation—and a new study shows it’s costing them valuable hours of sleep. But that’s not all: Kids and teens who look at screens before bed have higher BMIs than peers who put down the phones earlier in the evening.

“We also saw this technology use being associated with more fatigue in the morning, which circling back, is another risk factor for higher BMIs. So we’re seeing a loop pattern forming,” says study co-author Caitlyn Fuller.

For the study published in Global Pediatric Health, researchers from Penn State College of Medicine surveyed parents of 234 adolescents between the ages of 8 and 17 about the kids’ bedtime habits. This is what they found:

  • Kids who watched TV or played video games before bed averaged 30 fewer minutes of shut-eye
  • Kids who use their phones or computers right before attempting to shut down got an average 60 fewer minutes of sleep
  • All kids who used technology before bedtime were more prone to waking up during the night
  • Kids who used screens before bed had higher BMIs than peers who didn’t use screens

This sends a clear message to parents and pediatricians: Screen time and bed time don’t mix.

“Although there are many benefits to using technology, pediatricians may want to counsel parents about limiting technology for their kids, particularly at bedtime, to promote healthy childhood development and mental health,” says Dr. Marsha Novick, associate professor of pediatrics and family and community medicine.

With young kids spending way more time in front of screens than even a few years back, the boundaries parents work to create today are more important than ever. So, even when the sum of screen time hours is within the okay’ed amount, parents should work with their kids to minimize the minutes logged before bed.

As a suggestion: Winding down before bed is the perfect time to read a book. And, as great as Kindles can be, old-fashioned paper versions are pretty great, too.