Maybe parents should let their children sleep in a little more - it may help improve their behaviour and make them less restless in school, according to a Canadian study.

On the flip side, few parents are likely to be surprised to know that cutting back on children's sleep time seems to make them more likely to cry, lose their temper and become frustrated, according to the researchers, who published their findings in Pediatrics.

“You can think about it from a lot of different angles,” said Reut Gruber, of Montreal's McGill University and Douglas Research Centre, who led the study. “What we are showing here is that it can go both ways in terms of behaviour and academic performance.”

While Gruber's team is not the first to link sleep and behaviour, few studies have looked at whether more sleep actually leads to better behaviour in school children.

For the study, they recruited 33 children between seven and 11 years old to be followed over two weeks.

For the first week, the researchers monitored how long the children slept - about 9.3 hours, which is short of the 10 hours suggested by the US National Institutes of Health.

The children were split into two groups for the second week. One group's parents were told to add an hour to their kids' usual time asleep, while the other group was told to cut their sleep time by an hour.

Half of the children did lose an hour of sleep each night, but the other group was only able to add about 30 minutes. Still, that seemed long enough for teachers to notice an improvement in the kids' behaviour.

After the first week of monitoring, the teachers answered questions that rated the children's emotions, moodiness and restlessness at school on a scale from zero to 100, with higher scores indicating worse behaviour and scores above 60 indicating a behavioural problem.

The baseline score for both groups before the sleep manipulation began was about 50, but after a week of the experimental sleep changes teachers, who did not know which group any of the children were in, rated the kids again.

The children who got the extra 30 minutes of sleep during the second week scored, on average, about 47, meaning their behaviour had improved. But the children who lost an hour of sleep each night were scored about 54.

Gruber said that while the study only included 33 kids, it was still able to show that more sleep leads to better behaviour. But the parents' reporting of sleepiness and behaviour may have been influenced because of course they had to know how much more sleep their children were getting.

But she said it could be hard to add extra sleep in the evening, given how busy children's lives have become, and that perhaps adding just a little more in both morning and evening would help. - Reuters