For every hour of television a child watches each day, they get seven fewer minutes sleep.
U.S. researchers found boys are particularly likely to miss out on sleep because of the presence of a television in their bedroom.
Researchers at MassGeneral Hospital for Children and the Harvard School of Public Health followed more than 1,800 children from the age of six months to eight years.
They found that those who had a television in their bedroom got less sleep than those who didn’t.
They also discovered that children from ethnic minorities were much more likely to sleep in a room with a television.
And, among these children, the presence of a television reduced sleep duration by about half an hour a day.
The study participants, the children and their mothers, were enrolled in Project Viva – a long-term investigation into the health effects of several factors during pregnancy and after birth.
This study analysed information reported by mothers when the children were about six months old and then annually for the next seven years.
The information included details of how much time each day infants were in a room where a television was on, how much time older children watched television daily, whether children aged four to seven slept in a room where a TV was present and the children’s average daily amount of sleep.
The research was the first to study the effects of having a bedroom television over a long time period.
The study authors note their results support previous short-term studies finding that both television viewing and sleeping in a room with a television decrease total sleep time.
They say reduced sleep duration can have negative effects on both mental and physical health.