It’s clear kids are tired when parents find themselves having to pull at ankles or prod them every five minutes in order to get them moving in the morning, but what’s the source of their exhaustion?

Photo credit: Shutterstock

Photo credit: Shutterstock

While there are many factors at play, a recent study linked television with reduced sleep duration. It’s not the first to cite such findings but is the first to examine the connection over a several year period.

The study by researchers at Mass Hospital for Children and Harvard School of Public Health followed more than 1,800 children from 6 months to 7 years old. For every additional hour of television watched, investigators found the child slept seven minutes less. The effect was stronger in boys and for some ethnicities, the presence of a TV in a child’s bedroom was linked to up to 30 fewer minutes of sleep per day.

“I think in our case it’s possible that the content of the television watched may be different for boys than girls,” Elizabeth Cespedes, lead author of the study with Harvard, said, according to Reuters. “The content may be especially disruptive.”

“At all time points, racial and ethnic minority children in our study were sleeping a bit less and watching more television,” Cespedes added.

Dr. Heidi Connolly, a sleep specialist with the Golisano Children’s Hospital in New York, who was not involved with this study, told Reuters that it might be unreasonable to expect children to watch no TV at all, but limiting viewing to two hours or less is advisable.

“This doesn’t seem like very much, but if you think about it, seven minutes every night by the time you get to the end of the week you’re already a half hour short on sleep,” Connolly told Reuters.

The study was published in the journal Pediatrics.