Parents who are concerned that their children are always tired or are having difficulties concentrating should look at their media habits, scientists have said.

They claim that the more time a child spends on a computer or watching television, the more their sleep pattern is likely to be disrupted.

According to the scientists from Finland, previous studies have already suggested that the use of electronic media can affect a child's sleep. Since sleep directly affects a child's mental and physical health, including their performance in school, they decided to look into this further.

They looked at the sleep, TV viewing and computer use patterns of children aged 10 and 11. These patterns were then reassessed in the children 18 months later.

The study found that overall, a child's sleep tended to be more disrupted the more time they spent on their computer or watching TV. Those who spent the most time on these habits at the start of the study had the shortest sleep duration after 18 months.

The study also noted that those with a computer or TV in their bedroom tended to go to bed later than those without. This applied both on school days and at the weekend. This resulted in less sleep overall.

The scientists believe that parents should look at their children's media habits if they are concerned about their sleeping habits.

"Children need extra sleep as they go through puberty but our study finds that TV and computer use affect the sleep of children. This is especially true during the week and may be impacting their school work as well as their development.

"Media viewing habits should be considered for kids who are tired and struggling to concentrate, or who have behaviour problems caused by lack of sleep," the team from Folkhälsan Research Center said.

Details of these findings are published in the journal, BMC Public Health.