It shouldn’t come as too much of a surprise that a new study links lack of sleep in children to the amount of television they watch while they’re awake. And this isn’t the first time that researchers have cautioned parents to limit how much television their children consume.

The new study, published this week by the American Academy of Pediatrics, followed 1,800 children from infancy to about age 8. Researchers recorded how much time the children watched television starting at six months, and also noted if children had televisions in their bedrooms.

While the differences weren’t dramatic, they did find that for every extra hour of television a child watched, he or she slept seven fewer minutes a night. Kids with TVs in their rooms slept almost half an hour less than kids who didn’t. The effect on minority children was even greater.

Doctors and researchers have long warned parents against too much screen time for children and teens, who can commonly spend anywhere from eight to 11 hours per day in front of some sort of media screen (TV, computer, tablet or smartphone). Too much screen time has, for a long time, been linked to poor sleep, weight problems, low physical activity, mental health issues, daytime fatigue and lower academic achievements in kids and young adults.