Kiwi kids early to bed and get most sleep,

Our children are earliest to bed and get more hours sleep than those in other countries, says a new study.

A comparative study of a dozen countries shows children in New Zealand go to bed the earliest, and get the longest sleep.

The study - outlined in an oral presentation to the American Academy of Sleep Medicine conference which has just finished in Baltimore, Maryland - compared the sleep patterns of over 20,000 infants and toddlers aged up to three years.

Cultural differences meant that young children in predominately Caucasian countries, such as New Zealand, had earlier bedtimes and more overall sleep than young children in predominately Asian countries.

No differences were found in night wakings or napping behaviours.

Children in New Zealand went to bed the earliest with an average bedtime of 7.27pm, the study said. Children in Hong Kong went to bed the latest with an average bedtime of 10.17pm. United States children had an average bedtime of 8.52pm.

New Zealand children also had the highest total sleep time of 13.3 hours of nightly sleep and daytime naps. Japanese children had the least, of 11.6 hours a day and US children averaged 12.9 hours daily of total sleep time.

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The study, by Jodi Mindell, of Saint Joseph's University in Philadelphia, focused on 28,287 infants and toddlers, whose parents completed an extensive questionnaire.

"This study is the first one to ever look at sleep in infants and toddlers cross-culturally, and the results are astonishing," said Dr. Mindell.

"We found vast differences in amounts of sleep and parents' perceptions of sleep problems across countries."

Dr Mindell said 76 per cent of Chinese parents perceived that their child had a small or severe sleep problem, but only 11 per cent of parents in Taiwan had a similar concern.

The results brought more questions than answers, and key matters that need to be investigated include the extent to which the differences were simply the result of differing cultural practices, and what impact those differences were having on children.

The children studied included 1081 from New Zealand.

The American Academy of Sleep Medicine recommends newborns up to three months of age need about 16 to 20 hours of total sleep time per day, while infants between three and 12 months old need 14 to 15 hours of total sleep time.

Toddlers between the ages of one and four years need about 12 to 14 hours of total sleep time.

One important difference between countries was that children from the countries with mainly European populations were less likely than Asian children to be sharing a room.

The proportion of children sharing the bedroom ranged from 15.1 per cent in Canada to 94.5 per cent in Thailand.

Earlier this year, a New Zealand researcher, Professor Ed Mitchell, of Auckland University, published a paper in the scientific journal SLEEP which showed children who don't get enough nightly sleep were more likely to be overweight and have behavioural problems.

He studied 591 children, now aged seven, at birth, at one year, at three-and-a-half years and at seven years.

Prof Mitchell found the average time spent in bed was 10.1 hours, and the children's sleep duration was shorter on weekends than on weekdays. It was also shorter in summer, compared with spring, autumn and winter - and for children with no younger siblings, or for children whose bedtime was after 9pm.

Children who slept less than nine hours were three times more likely to be overweight or obese and to have a 3.34 per cent increase in body fat than those who slept for more than nine hours.

Short sleep duration was also associated with higher emotional liability scores.

Prof Mitchell recommended that children in pre-school sleep between 11-13 hours a night and school-aged children between 10-11 hours of sleep a night.