Children as young as eight may already show unhealthy sleeping habits normally associated with adolescence according to new research, which could be affecting their school performance and health.

Carried out by researchers at McGill University in Montreal, the new study looked at the sleep patterns of 144 children aged six to 11 years old during the academic year.

Participants were divided into three age groups, 6-7 years; 8-9 years; and 10-11 years, with each participant's sleep pattern assessed over seven nights using a miniature actigraph, a wristwatch-like device that measures movement to evaluate sleep.

The recordings showed that the older the children were, the greater and more significant the delay in sleep start time and the shorter their sleep duration.

Only 17 per cent of children aged 6-7 got the recommended amount of sleep, with this figure dropping to just 2.5 per cent for those aged 10-11.

In addition, the team found that those aged 8-11 increasingly showed unhealthy sleep patterns usually found in teenagers, such as later bedtimes, inconsistent sleep schedules, and sleep deprivation.

Poor sleep patterns have previously been shown to impair academic performance at school, as well as children's physical and mental health.

"Our findings contradict the prevailing assumption that sleep patterns remain largely unchanged during the school-age period, from six to 13 years old," says Reut Gruber, an associate professor in McGill's Department of Psychiatry and lead author of the study, adding that the findings "highlight the importance of boundaries related to bedtime that parents should consider setting for their children even as they get older and more independent."

These boundaries include setting a regular time for bed, a regular time to wake up, teaching children the importance of sleep for school and health, and encouraging children to get sufficient amount of good quality sleep, as well as seeking help if they are having sleep problems.

The American Academy of Pediatrics recommends that children 6 to 12 years of age should sleep 9 to 12 hours per 24 hours on a regular basis for optimal health. Teenagers 13 to 18 years of age should aim to get 8 to 10 hours sleep.

The findings are to be published in the journal Sleep Medicine.