A new study appears to confirm the theory that children who watch a lot of television sleep less.

US researchers monitored the progress of over 1,800 children from when they were six months old to when they were almost eight years old. The mothers of the children were asked every year about the children's television and sleeping habits.

The study found a small but consistent link between increased television watching and reduced sleep duration. Every additional hour of TV watched by the children was associated with seven fewer minutes of sleep per day. This link appeared to be stronger in boys than in girls.

If a child had a television in their bedroom, they were even more likely to sleep less. In fact, having a TV in their room reduced a child's average amount of sleep by 30 minutes per day.

The researchers said that these findings support other studies that have found a link between TV viewing and sleep time, particularly if a TV is located in a child's bedroom.

Details of these findings are published in the journal, Pediatrics.